KeyedCollectionとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

KeyedCollection コンストラクタ ()

メモ : このコンストラクタは、.NET Framework version 2.0 で新しく追加されたものです。

既定の等値比較演算子を使用する KeyedCollection クラスの新しいインスタンスを初期化します。

名前空間: System.Collections.ObjectModel
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Protected Sub New

Visual Basic (使用法)

Dim instance As New KeyedCollection(Of
 TKey, TItem)

protected KeyedCollection ()

C++

protected:
KeyedCollection ()

protected KeyedCollection ()

JScript

protected function KeyedCollection ()

解説

このコンストラクタで作成された KeyedCollection は、EqualityComparer.Default から取得する、キーの型の既定のジェネリック等値比較演算子を使用します。異なるジェネリック等値比較演算子を指定するには、KeyedCollection(ジェネリック IEqualityComparer) コンストラクタまたは KeyedCollection(ジェネリック IEqualityComparer,Int32) コンストラクタを使用します。

既定では、KeyedCollection には最初の項目の追加時に作成される検索ディクショナリが含まれます。高速な検索を可能にするため、KeyedCollection に項目が追加されると、項目のキーが 1 度だけ抽出され、検索ディクショナリに保存されます。この動作は、KeyedCollection(ジェネリック IEqualityComparer,Int32) コンストラクタを使用し、ディクショナリ作成のしきい値を指定することによりオーバーライドできます。

メモ
KeyedCollection クラスは抽象クラス (Visual Basic の場合は MustInherit) なので、使用するためにはこのクラスから派生させる必要があります。派生型のコンストラクタで、適切な KeyedCollection コンストラクタを呼び出します。コンストラクタ内の等値比較演算子やディクショナリ作成のしきい値のように機能を公開する必要はありません。

メモ

KeyedCollection クラスは抽象クラス (Visual Basic の場合は MustInherit) なので、使用するためにはこのクラスから派生させる必要があります。派生型のコンストラクタで、適切な KeyedCollection コンストラクタを呼び出します。コンストラクタ内の等値比較演算子やディクショナリ作成のしきい値のように機能を公開する必要はありません。

このコンストラクタは O(1) 操作です。

使用例

このコード例は、KeyedCollection からコレクションクラスを派生させるために必要な最小限のコードを示しています。GetKeyForItem メソッドをオーバーライドし、基本クラスコンストラクタに処理を代行させるパブリックコンストラクタを用意しています。また、KeyedCollection クラスおよび Collection クラスから継承されたプロパティおよびメソッドも多数示しています。

SimpleOrder クラスは、OrderItem オブジェクトを含んでいる非常に単純な発注リストです。各オブジェクトは行項目を順番に表します。OrderItem のキーは変更できません。これは、KeyedCollection の派生クラスを使用する際に考慮する必要がある重要な事項です。変更可能なキーを使用するコード例の詳細については、ChangeItemKey のトピックを参照してください。

Visual Basic

Imports System
Imports System.Collections.Generic
Imports System.Collections.ObjectModel

' This class represents a very simple keyed list of OrderItems,
' inheriting most of its behavior from the KeyedCollection and 
' Collection classes. The immediate base class is the constructed
' type KeyedCollection(Of Integer, OrderItem). When you inherit
' from KeyedCollection, the second generic type argument is the 
' type that you want to store in the collection -- in this case
' OrderItem. The first generic argument is the type that you want
' to use as a key. Its values must be calculated from OrderItem; 
' in this case it is the Integer field PartNumber, so SimpleOrder
' inherits KeyedCollection(Of Integer, OrderItem).
'
Public Class SimpleOrder
    Inherits KeyedCollection(Of Integer,
 OrderItem)

    ' The parameterless constructor of the base class creates a 
    ' KeyedCollection with an internal dictionary. For this code 
    ' example, no other constructors are exposed.
    '
    Public Sub New()
        MyBase.New()
    End Sub
    
    ' This is the only method that absolutely must be overridden,
    ' because without it the KeyedCollection cannot extract the
    ' keys from the items. The input parameter type is the 
    ' second generic type argument, in this case OrderItem, and 
    ' the return value type is the first generic type argument,
    ' in this case Integer.
    '
    Protected Overrides Function
 GetKeyForItem( _
        ByVal item As OrderItem) As
 Integer

        ' In this example, the key is the part number.
        Return item.PartNumber   
    End Function

End Class

Public Class Demo
    
    Public Shared Sub Main()
 
        Dim weekly As New
 SimpleOrder()

        ' The Add method, inherited from Collection, takes OrderItem.
        '
        weekly.Add(New OrderItem(110072674, "Widget",
 400, 45.17))
        weekly.Add(New OrderItem(110072675, "Sprocket",
 27, 5.3))
        weekly.Add(New OrderItem(101030411, "Motor",
 10, 237.5))
        weekly.Add(New OrderItem(110072684, "Gear",
 175, 5.17))
        
        Display(weekly)
    
        ' The Contains method of KeyedCollection takes TKey.
        '
        Console.WriteLine(vbLf & "Contains(101030411): {0}",
 _
            weekly.Contains(101030411))

        ' The default Item property of KeyedCollection takes the key
        ' type, Integer.
        '
        Console.WriteLine(vbLf & "weekly(101030411).Description:
 {0}", _
            weekly(101030411).Description)

        ' The Remove method of KeyedCollection takes a key.
        '
        Console.WriteLine(vbLf & "Remove(101030411)")
        weekly.Remove(101030411)
        Display(weekly)

        ' The Insert method, inherited from Collection, takes an 
        ' index and an OrderItem.
        '
        Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
        weekly.Insert(2, New OrderItem(111033401, "Nut",
 10, .5))
        Display(weekly)

        ' The default Item property is overloaded. One overload comes
        ' from KeyedCollection(Of Integer, OrderItem); that overload
        ' is read-only, and takes Integer because it retrieves by key.
 
        ' The other overload comes from Collection(Of OrderItem), the
 
        ' base class of KeyedCollection(Of Integer, OrderItem); it 
        ' retrieves by index, so it also takes an Integer. The compiler
        ' uses the most-derived overload, from KeyedCollection, so the
        ' only way to access SimpleOrder by index is to cast it to
        ' Collection(Of OrderItem). Otherwise the index is interpreted
        ' as a key, and KeyNotFoundException is thrown.
        '
        Dim coweekly As Collection(Of
 OrderItem) = weekly
        Console.WriteLine(vbLf & "coweekly(2).Description:
 {0}", _
            coweekly(2).Description)
 
        Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
        coweekly(2) = New OrderItem(127700026, "Crank",
 27, 5.98)

        Dim temp As OrderItem = coweekly(2)

        ' The IndexOf method, inherited from Collection(Of OrderItem),
 
        ' takes an OrderItem instead of a key.
        ' 
        Console.WriteLine(vbLf & "IndexOf(temp): {0}",
 _
            weekly.IndexOf(temp))

        ' The inherited Remove method also takes an OrderItem.
        '
        Console.WriteLine(vbLf & "Remove(temp)")
        weekly.Remove(temp)
        Display(weekly)

        Console.WriteLine(vbLf & "RemoveAt(0)")
        weekly.RemoveAt(0)
        Display(weekly)

    End Sub
    
    Private Shared Sub Display(ByVal
 order As SimpleOrder) 
        Console.WriteLine()
        For Each item As
 OrderItem In  order
            Console.WriteLine(item)
        Next item
    End Sub
End Class

' This class represents a simple line item in an order. All the 
' values are immutable except quantity.
' 
Public Class OrderItem
    Public ReadOnly PartNumber As
 Integer
    Public ReadOnly Description As
 String
    Public ReadOnly UnitPrice As
 Double
    
    Private _quantity As Integer
 = 0
    
    Public Sub New(ByVal
 partNumber As Integer, _
                   ByVal description As String,
 _
                   ByVal quantity As Integer,
 _
                   ByVal unitPrice As Double)
 
        Me.PartNumber = partNumber
        Me.Description = description
        Me.Quantity = quantity
        Me.UnitPrice = unitPrice
    End Sub 'New
    
    Public Property Quantity() As
 Integer 
        Get
            Return _quantity
        End Get
        Set
            If value < 0 Then
                Throw New ArgumentException("Quantity
 cannot be negative.")
            End If
            _quantity = value
        End Set
    End Property
        
    Public Overrides Function
 ToString() As String 
        Return String.Format( _
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 _
            PartNumber, _quantity, Description, UnitPrice, _
            UnitPrice * _quantity)
    End Function
End Class

' This code example produces the following output:
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'101030411     10 Motor        at   237.50 =   2,375.00
'110072684    175 Gear         at     5.17 =     904.75
'
'Contains(101030411): True
'
'weekly(101030411).Description: Motor
'
'Remove(101030411)
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684    175 Gear         at     5.17 =     904.75
'
'Insert(2, New OrderItem(...))
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'111033401     10 Nut          at      .50 =       5.00
'110072684    175 Gear         at     5.17 =     904.75
'
'coweekly(2).Description: Nut
'
'coweekly(2) = New OrderItem(...)
'
'IndexOf(temp): 2
'
'Remove(temp)
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684    175 Gear         at     5.17 =     904.75
'
'RemoveAt(0)
'
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684    175 Gear         at     5.17 =     904.75

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

// This class represents a very simple keyed list of OrderItems,
// inheriting most of its behavior from the KeyedCollection and 
// Collection classes. The immediate base class is the constructed
// type KeyedCollection<int, OrderItem>. When you inherit
// from KeyedCollection, the second generic type argument is the 
// type that you want to store in the collection -- in this case
// OrderItem. The first type argument is the type that you want
// to use as a key. Its values must be calculated from OrderItem; 
// in this case it is the int field PartNumber, so SimpleOrder
// inherits KeyedCollection<int, OrderItem>.
//
public class SimpleOrder : KeyedCollection<int,
 OrderItem>
{
    // The parameterless constructor of the base class creates a 
    // KeyedCollection with an internal dictionary. For this code 
    // example, no other constructors are exposed.
    //
    public SimpleOrder() : base() {}
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. The input parameter type is the 
    // second generic type argument, in this case OrderItem, and 
    // the return value type is the first generic type argument,
    // in this case int.
    //
    protected override int GetKeyForItem(OrderItem
 item)
    {
        // In this example, the key is the part number.
        return item.PartNumber;
    }
}

public class Demo
{    
    public static void Main()
    {
        SimpleOrder weekly = new SimpleOrder();

        // The Add method, inherited from Collection, takes OrderItem.
        //
        weekly.Add(new OrderItem(110072674, "Widget",
 400, 45.17));
        weekly.Add(new OrderItem(110072675, "Sprocket",
 27, 5.3));
        weekly.Add(new OrderItem(101030411, "Motor",
 10, 237.5));
        weekly.Add(new OrderItem(110072684, "Gear",
 175, 5.17));
        
        Display(weekly);
    
        // The Contains method of KeyedCollection takes the key, 
        // type, in this case int.
        //
        Console.WriteLine("\nContains(101030411): {0}", 
            weekly.Contains(101030411));

        // The default Item property of KeyedCollection takes a key.
        //
        Console.WriteLine("\nweekly[101030411].Description: {0}", 
            weekly[101030411].Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console.WriteLine("\nRemove(101030411)");
        weekly.Remove(101030411);
        Display(weekly);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console.WriteLine("\nInsert(2, New OrderItem(...))");
        weekly.Insert(2, new OrderItem(111033401, "Nut",
 10, .5));
        Display(weekly);

        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem> coweekly = weekly;
        Console.WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2].Description);
 
        Console.WriteLine("\ncoweekly[2] = new OrderItem(...)");
        coweekly[2] = new OrderItem(127700026, "Crank",
 27, 5.98);

        OrderItem temp = coweekly[2];

        // The IndexOf method inherited from Collection<OrderItem>
 
        // takes an OrderItem instead of a key
        // 
        Console.WriteLine("\nIndexOf(temp): {0}", weekly.IndexOf(temp));

        // The inherited Remove method also takes an OrderItem.
        //
        Console.WriteLine("\nRemove(temp)");
        weekly.Remove(temp);
        Display(weekly);

        Console.WriteLine("\nRemoveAt(0)");
        weekly.RemoveAt(0);
        Display(weekly);

    }
    
    private static void
 Display(SimpleOrder order)
    {
        Console.WriteLine();
        foreach( OrderItem item in order )
        {
            Console.WriteLine(item);
        }
    }
}

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public class OrderItem
{
    public readonly int PartNumber;
    public readonly string Description;
    public readonly double UnitPrice;
    
    private int _quantity = 0;
    
    public OrderItem(int partNumber, string
 description, 
        int quantity, double unitPrice)
    {
        this.PartNumber = partNumber;
        this.Description = description;
        this.Quantity = quantity;
        this.UnitPrice = unitPrice;
    } 
    
    public int Quantity    
    {
        get { return _quantity; }
        set
        {
            if (value<0)
                throw new ArgumentException("Quantity cannot
 be negative.");
            
            _quantity = value;
        }
    }
        
    public override string ToString()
    {
        return String.Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    }
}

/* This code example produces the following output:

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly[101030411].Description: Motor

Remove(101030411)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

Insert(2, New OrderItem(...))

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
111033401     10 Nut          at      .50 =       5.00
110072684    175 Gear         at     5.17 =     904.75

coweekly[2].Description: Nut

coweekly[2] = new OrderItem(...)

IndexOf(temp): 2

Remove(temp)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

RemoveAt(0)

110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75
 */

C++

using namespace System;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public ref class OrderItem
{
private:
    int _quantity;
    
public:
    initonly int PartNumber;
    initonly String^ Description;
    initonly double UnitPrice;
    
    OrderItem(int partNumber, String^ description, 
        int quantity, double unitPrice)
    {
        this->PartNumber = partNumber;
        this->Description = description;
        this->Quantity = quantity;
        this->UnitPrice = unitPrice;
    } 
    
    property int Quantity    
    {
        int get() { return
 _quantity; }
        void set(int value)
        {
            if (value < 0)
                throw gcnew ArgumentException("Quantity cannot be negative.");
            
            _quantity = value;
        }
    }
        
    virtual String^ ToString() override 
    {
        return String::Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    }
};

// This class represents a very simple keyed list of OrderItems,
// inheriting most of its behavior from the KeyedCollection and 
// Collection classes. The immediate base class is the constructed
// type KeyedCollection<int, OrderItem>. When you inherit
// from KeyedCollection, the second generic type argument is the 
// type that you want to store in the collection -- in this case
// OrderItem. The first type argument is the type that you want
// to use as a key. Its values must be calculated from OrderItem; 
// in this case it is the int field PartNumber, so SimpleOrder
// inherits KeyedCollection<int, OrderItem>.
//
public ref class SimpleOrder : KeyedCollection<int,
 OrderItem^>
{
    // The parameterless constructor of the base class creates a 
    // KeyedCollection with an internal dictionary. For this code 
    // example, no other constructors are exposed.
    //
public:
    SimpleOrder() {}
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. The input parameter type is the 
    // second generic type argument, in this case OrderItem, and 
    // the return value type is the first generic type argument,
    // in this case int.
    //
protected:
    virtual int GetKeyForItem(OrderItem^ item) override 
    {
        // In this example, the key is the part number.
        return item->PartNumber;
    }
};

public ref class Demo
{    
public:
    static void Main()
    {
        SimpleOrder^ weekly = gcnew SimpleOrder();

        // The Add method, inherited from Collection, takes OrderItem.
        //
        weekly->Add(gcnew OrderItem(110072674, "Widget", 400, 45.17));
        weekly->Add(gcnew OrderItem(110072675, "Sprocket", 27, 5.3));
        weekly->Add(gcnew OrderItem(101030411, "Motor", 10, 237.5));
        weekly->Add(gcnew OrderItem(110072684, "Gear", 175, 5.17));
        
        Display(weekly);
    
        // The Contains method of KeyedCollection takes the key, 
        // type, in this case int.
        //
        Console::WriteLine("\nContains(101030411): {0}", 
            weekly->Contains(101030411));

        // The default Item property of KeyedCollection takes a key.
        //
        Console::WriteLine("\nweekly(101030411)->Description: {0}",
 
            weekly[101030411]->Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console::WriteLine("\nRemove(101030411)");
        weekly->Remove(101030411);
        Display(weekly);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console::WriteLine("\nInsert(2, New OrderItem(...))");
        weekly->Insert(2, gcnew OrderItem(111033401, "Nut", 10, .5));
        Display(weekly);

        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem^>^ coweekly = weekly;
        Console::WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2]->Description);
 
        Console::WriteLine("\ncoweekly[2] = gcnew OrderItem(...)");
        coweekly[2] = gcnew OrderItem(127700026, "Crank", 27, 5.98);

        OrderItem^ temp = coweekly[2];

        // The IndexOf method inherited from Collection<OrderItem>
 
        // takes an OrderItem instead of a key
        // 
        Console::WriteLine("\nIndexOf(temp): {0}", weekly->IndexOf(temp));

        // The inherited Remove method also takes an OrderItem.
        //
        Console::WriteLine("\nRemove(temp)");
        weekly->Remove(temp);
        Display(weekly);

        Console::WriteLine("\nRemoveAt(0)");
        weekly->RemoveAt(0);
        Display(weekly);

    }
    
private:
    static void Display(SimpleOrder^ order)
    {
        Console::WriteLine();
        for each( OrderItem^ item in order
 )
        {
            Console::WriteLine(item);
        }
    }
};

void main()
{
    Demo::Main();
}

/* This code example produces the following output:

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly(101030411)->Description: Motor

Remove(101030411)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

Insert(2, New OrderItem(...))

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
111033401     10 Nut          at      .50 =       5.00
110072684    175 Gear         at     5.17 =     904.75

coweekly(2)->Description: Nut

coweekly[2] = gcnew OrderItem(...)

IndexOf(temp): 2

Remove(temp)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

RemoveAt(0)

110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75
 */

プラットフォーム

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0
.NET Compact Framework
サポート対象 : 2.0

参照

関連項目
KeyedCollection ジェネリッククラス
KeyedCollection メンバ
System.Collections.ObjectModel 名前空間
IEqualityComparer ジェネリックインターフェイス

KeyedCollection コンストラクタ

KeyedCollection クラスの新しいインスタンスを初期化します。
オーバーロードの一覧

名前	説明
KeyedCollection ()	既定の等値比較演算子を使用する KeyedCollection クラスの新しいインスタンスを初期化します。 .NET Compact Framework によってサポートされています。
KeyedCollection (ジェネリック IEqualityComparer)	指定した等値比較演算子を使用する KeyedCollection クラスの新しいインスタンスを初期化します。 .NET Compact Framework によってサポートされています。
KeyedCollection (ジェネリック IEqualityComparer, Int32)	指定した等値比較演算子を使用し、指定したしきい値を超えた場合に検索ディクショナリを作成する、KeyedCollection クラスの新しいインスタンスを初期化します。 .NET Compact Framework によってサポートされています。

参照

KeyedCollection コンストラクタ (ジェネリック IEqualityComparer)

メモ : このコンストラクタは、.NET Framework version 2.0 で新しく追加されたものです。

指定した等値比較演算子を使用する KeyedCollection クラスの新しいインスタンスを初期化します。

名前空間: System.Collections.ObjectModel
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Protected Sub New ( _
    comparer As IEqualityComparer(Of TKey)
 _
)

Visual Basic (使用法)

Dim comparer As IEqualityComparer(Of
 TKey)

Dim instance As New KeyedCollection(Of
 TKey, TItem)(comparer)

protected KeyedCollection (
    IEqualityComparer<TKey> comparer
)

C++

protected:
KeyedCollection (
    IEqualityComparer<TKey>^ comparer
)

protected KeyedCollection (
    IEqualityComparer<TKey> comparer
)

JScript

protected function KeyedCollection (
    comparer : IEqualityComparer<TKey>
)

パラメータ

comparer: キーを比較する場合に使用する IEqualityComparer ジェネリックインターフェイスの実装。または、EqualityComparer.Default から取得する、キーの型の既定の等値比較演算子を使用する場合は null 参照 (Visual Basic では Nothing)。

解説

既定では、KeyedCollection には最初の項目の追加時に作成される検索ディクショナリが含まれます。高速な検索を可能にするため、KeyedCollection に項目が追加されると、項目のキーが 1 度だけ抽出され、検索ディクショナリに保存されます。この動作は、KeyedCollection(ジェネリック IEqualityComparer,Int32) コンストラクタを使用し、ディクショナリ作成のしきい値を指定することによりオーバーライドできます。

メモ
KeyedCollection クラスは抽象クラス (Visual Basic の場合は MustInherit) なので、使用するためにはこのクラスから派生させる必要があります。派生型のコンストラクタで、適切な KeyedCollection コンストラクタを呼び出します。コンストラクタ内の等値比較演算子やディクショナリ作成のしきい値のように機能を公開する必要はありません。

メモ

このコンストラクタは O(1) 操作です。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0
.NET Compact Framework
サポート対象 : 2.0

参照

関連項目
KeyedCollection ジェネリッククラス
KeyedCollection メンバ
System.Collections.ObjectModel 名前空間
IEqualityComparer ジェネリックインターフェイス

KeyedCollection コンストラクタ (ジェネリック IEqualityComparer, Int32)

メモ : このコンストラクタは、.NET Framework version 2.0 で新しく追加されたものです。

指定した等値比較演算子を使用し、指定したしきい値を超えた場合に検索ディクショナリを作成する、KeyedCollection クラスの新しいインスタンスを初期化します。

名前空間: System.Collections.ObjectModel
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Protected Sub New ( _
    comparer As IEqualityComparer(Of TKey),
 _
    dictionaryCreationThreshold As Integer
 _
)

Visual Basic (使用法)

Dim comparer As IEqualityComparer(Of
 TKey)
Dim dictionaryCreationThreshold As Integer

Dim instance As New KeyedCollection(Of
 TKey, TItem)(comparer, dictionaryCreationThreshold)

protected KeyedCollection (
    IEqualityComparer<TKey> comparer,
    int dictionaryCreationThreshold
)

C++

protected:
KeyedCollection (
    IEqualityComparer<TKey>^ comparer, 
    int dictionaryCreationThreshold
)

protected KeyedCollection (
    IEqualityComparer<TKey> comparer, 
    int dictionaryCreationThreshold
)

JScript

protected function KeyedCollection (
    comparer : IEqualityComparer<TKey>, 
    dictionaryCreationThreshold : int
)

パラメータ

comparer: キーを比較する場合に使用する IEqualityComparer ジェネリックインターフェイスの実装。または、EqualityComparer.Default から取得する、キーの型の既定の等値比較演算子を使用する場合は null 参照 (Visual Basic では Nothing)。

dictionaryCreationThreshold: 検索ディクショナリを作成せずにコレクションが保有できる要素数 (0 を指定すると最初の項目の追加時に検索ディクショナリが作成される)。検索ディクショナリを作成しない場合は -1。

例外

例外の種類	条件
ArgumentOutOfRangeException	dictionaryCreationThreshold が –1 未満です。

解説

既定では、KeyedCollection には最初の項目の追加時に作成される検索ディクショナリが含まれます。高速な検索を可能にするため、KeyedCollection に項目が追加されると、項目のキーが 1 度だけ抽出され、検索ディクショナリに保存されます。このコンストラクタでは動作をオーバーライドできます。0 を指定すると、最初の要素の追加時にディクショナリが作成され、1 を指定すると 2 番目の要素の追加時にディクショナリが作成されます。以降も同様です。しきい値として –1 を指定した場合、検索ディクショナリは作成されません。

非常に小さいコレクションの場合、検索ディクショナリによって実現する検索速度の向上効果が、ディクショナリによる必要メモリ量の増加に見合わない可能性があります。しきい値を設定することにより、このトレードオフについて判断を切り替える境界を決定できます。

メモ
KeyedCollection クラスは抽象クラス (Visual Basic の場合は MustInherit) なので、使用するためにはこのクラスから派生させる必要があります。派生型のコンストラクタで、適切な KeyedCollection コンストラクタを呼び出します。コンストラクタ内の等値比較演算子やディクショナリ作成のしきい値のように機能を公開する必要はありません。

メモ

このコンストラクタは O(1) 操作です。

使用例

このコード例では、InsertItem、RemoveItem、ClearItems、および SetItem の各プロテクトメソッドをオーバーライドする方法を示し、Add、Remove、および Clear の各メソッドのカスタム動作と、既定の Item プロパティ (C# の場合はインデクサ) を設定するためのカスタム動作を提供します。この例で提供されるカスタム動作は、Changed という名前の通知イベントです。これは、オーバーライドされた各メソッドの最後で発生します。

このコード例では、しきい値を 0 に設定して KeyedCollection(ジェネリック IEqualityComparer,Int32) コンストラクタを使用するため、オブジェクトがコレクションに最初に追加されたときに内部ディクショナリが作成されます。

このコード例では、SimpleOrder クラスを作成します。このクラスは、KeyedCollection から派生し、単純な注文フォームを表しています。この注文フォームには、注文する項目を表す OrderItem オブジェクトが含まれています。また、イベント情報や、変更の種類を識別する列挙を含めるために、SimpleOrderChangedEventArgs クラスも作成します。

Demo クラスの Main メソッドで、派生クラスのプロパティおよびメソッドを呼び出すことにより、カスタム動作の例を示します。

このコード例では、変更できないキーを持つオブジェクトを使用します。変更可能なキーを使用するコード例の詳細については、ChangeItemKey のトピックを参照してください。

Visual Basic

Imports System
Imports System.Collections.Generic
Imports System.Collections.ObjectModel

' This class derives from KeyedCollection and shows how to override
' the protected ClearItems, InsertItem, RemoveItem, and SetItem 
' methods in order to change the behavior of the default Item 
' property and the Add, Clear, Insert, and Remove methods. The
' class implements a Changed event, which is raised by all the
' protected methods.
'
' SimpleOrder is a collection of OrderItem objects, and its key
' is the PartNumber field of OrderItem. PartNumber is an Integer,
' so SimpleOrder inherits KeyedCollection(Of Integer, OrderItem).
' (Note that the key of OrderItem cannot be changed; if it could 
' be changed, SimpleOrder would have to override ChangeItemKey.)
'
Public Class SimpleOrder
    Inherits KeyedCollection(Of Integer,
 OrderItem)

    Public Event Changed As
 EventHandler(Of SimpleOrderChangedEventArgs)

    ' This parameterless constructor calls the base class constructor
    ' that specifies a dictionary threshold of 0, so that the internal
    ' dictionary is created as soon as an item is added to the 
    ' collection.
    '
    Public Sub New()
        MyBase.New(Nothing, 0)
    End Sub
    
    ' This is the only method that absolutely must be overridden,
    ' because without it the KeyedCollection cannot extract the
    ' keys from the items. 
    '
    Protected Overrides Function
 GetKeyForItem( _
        ByVal item As OrderItem) As
 Integer

        ' In this example, the key is the part number.
        Return item.PartNumber   
    End Function

    Protected Overrides Sub
 InsertItem( _
        ByVal index As Integer,
 ByVal newItem As OrderItem)

        MyBase.InsertItem(index, newItem)

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Added, newItem, Nothing))
    End Sub

    Protected Overrides Sub
 SetItem(ByVal index As Integer,
 _
        ByVal newItem As OrderItem)

        Dim replaced As OrderItem = Items(index)
        MyBase.SetItem(index, newItem)

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Replaced, replaced, newItem))
    End Sub

    Protected Overrides Sub
 RemoveItem(ByVal index As Integer)

        Dim removedItem As OrderItem = Items(index)
        MyBase.RemoveItem(index)

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Removed, removedItem, Nothing))
    End Sub

    Protected Overrides Sub
 ClearItems()
        MyBase.ClearItems()

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Cleared, Nothing, Nothing))
    End Sub

End Class

' Event argument for the Changed event.
'
Public Class SimpleOrderChangedEventArgs
    Inherits EventArgs

    Private _changedItem As OrderItem
    Private _changeType As ChangeType
    Private _replacedWith As OrderItem

    Public ReadOnly Property
 ChangedItem As OrderItem
        Get
            Return _changedItem
        End Get
    End Property

    Public ReadOnly Property
 ChangeType As ChangeType
        Get
            Return _changeType
        End Get
    End Property

    Public ReadOnly Property
 ReplacedWith As OrderItem
        Get
            Return _replacedWith
        End Get
    End Property

    Public Sub New(ByVal
 change As ChangeType, ByVal item As
 OrderItem, _
        ByVal replacement As OrderItem)

        _changeType = change
        _changedItem = item
        _replacedWith = replacement
    End Sub
End Class

Public Enum ChangeType
    Added
    Removed
    Replaced
    Cleared
End Enum

Public Class Demo
    
    Public Shared Sub Main()
 
        Dim weekly As New
 SimpleOrder()
        AddHandler weekly.Changed, AddressOf
 ChangedHandler

        ' The Add method, inherited from Collection, takes OrderItem.
        '
        weekly.Add(New OrderItem(110072674, "Widget",
 400, 45.17))
        weekly.Add(New OrderItem(110072675, "Sprocket",
 27, 5.3))
        weekly.Add(New OrderItem(101030411, "Motor",
 10, 237.5))
        weekly.Add(New OrderItem(110072684, "Gear",
 175, 5.17))

        Display(weekly)
        
        ' The Contains method of KeyedCollection takes TKey.
        '
        Console.WriteLine(vbLf & "Contains(101030411): {0}",
 _
            weekly.Contains(101030411))

        ' The default Item property of KeyedCollection takes the key
        ' type, Integer. The property is read-only.
        '
        Console.WriteLine(vbLf & "weekly(101030411).Description:
 {0}", _
            weekly(101030411).Description)

        ' The Remove method of KeyedCollection takes a key.
        '
        Console.WriteLine(vbLf & "Remove(101030411)")
        weekly.Remove(101030411)

        ' The Insert method, inherited from Collection, takes an 
        ' index and an OrderItem.
        '
        Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
        weekly.Insert(2, New OrderItem(111033401, "Nut",
 10, .5))
         
        ' The default Item property is overloaded. One overload comes
        ' from KeyedCollection(Of Integer, OrderItem); that overload
        ' is read-only, and takes Integer because it retrieves by key.
 
        ' The other overload comes from Collection(Of OrderItem), the
 
        ' base class of KeyedCollection(Of Integer, OrderItem); it 
        ' retrieves by index, so it also takes an Integer. The compiler
        ' uses the most-derived overload, from KeyedCollection, so the
        ' only way to access SimpleOrder by index is to cast it to
        ' Collection(Of OrderItem). Otherwise the index is interpreted
        ' as a key, and KeyNotFoundException is thrown.
        '
        Dim coweekly As Collection(Of
 OrderItem) = weekly
        Console.WriteLine(vbLf & "coweekly(2).Description:
 {0}", _
            coweekly(2).Description)
 
        Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
        coweekly(2) = New OrderItem(127700026, "Crank",
 27, 5.98)

        Dim temp As OrderItem = coweekly(2)

        ' The IndexOf method, inherited from Collection(Of OrderItem),
 
        ' takes an OrderItem instead of a key.
        ' 
        Console.WriteLine(vbLf & "IndexOf(temp): {0}",
 _
            weekly.IndexOf(temp))

        ' The inherited Remove method also takes an OrderItem.
        '
        Console.WriteLine(vbLf & "Remove(temp)")
        weekly.Remove(temp)

        Console.WriteLine(vbLf & "RemoveAt(0)")
        weekly.RemoveAt(0)

        ' Increase the quantity for a line item.
        Console.WriteLine(vbLf & "coweekly(1) = New OrderItem(...)")
        coweekly(1) = New OrderItem(coweekly(1).PartNumber, _
            coweekly(1).Description, coweekly(1).Quantity + 1000, _
            coweekly(1).UnitPrice)

        Display(weekly)

        Console.WriteLine()
        weekly.Clear()
    End Sub
    
    Private Shared Sub Display(ByVal
 order As SimpleOrder) 
        Console.WriteLine()
        For Each item As
 OrderItem In  order
            Console.WriteLine(item)
        Next item
    End Sub

    Private Shared Sub ChangedHandler(ByVal
 source As Object, _
        ByVal e As SimpleOrderChangedEventArgs)

        Dim item As OrderItem = e.ChangedItem

        If e.ChangeType = ChangeType.Replaced Then
            Dim replacement As OrderItem =
 e.ReplacedWith

            Console.WriteLine("{0} (quantity {1}) was replaced
 " & _
                "by {2}, (quantity {3}).", item.Description,
 _
                item.Quantity, replacement.Description, replacement.Quantity)

        ElseIf e.ChangeType = ChangeType.Cleared Then
            Console.WriteLine("The order list was cleared.")

        Else
            Console.WriteLine("{0} (quantity {1}) was {2}.",
 _
                item.Description, item.Quantity, e.ChangeType)
        End If
    End Sub
End Class

' This class represents a simple line item in an order. All the 
' values are immutable except quantity.
' 
Public Class OrderItem
    
    Private _partNumber As Integer
    Private _description As String
    Private _unitPrice As Double
    Private _quantity As Integer

    Public ReadOnly Property
 PartNumber As Integer
        Get
            Return _partNumber
        End Get
    End Property

    Public ReadOnly Property
 Description As String
        Get
            Return _description
        End Get
    End Property

    Public ReadOnly Property
 UnitPrice As Double
        Get
            Return _unitPrice
        End Get
    End Property
    
    Public ReadOnly Property
 Quantity() As Integer 
        Get
            Return _quantity
        End Get
    End Property
    
    Public Sub New(ByVal
 partNumber As Integer, _
                   ByVal description As String,
 _
                   ByVal quantity As Integer,
 _
                   ByVal unitPrice As Double)
 
        _partNumber = partNumber
        _description = description
        _quantity = quantity
        _unitPrice = unitPrice
    End Sub 'New
        
    Public Overrides Function
 ToString() As String 
        Return String.Format( _
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 _
            PartNumber, _quantity, Description, UnitPrice, _
            UnitPrice * _quantity)
    End Function
End Class

' This code example produces the following output:
'
'Widget (quantity 400) was Added.
'Sprocket (quantity 27) was Added.
'Motor (quantity 10) was Added.
'Gear (quantity 175) was Added.
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'101030411     10 Motor        at   237.50 =   2,375.00
'110072684    175 Gear         at     5.17 =     904.75
'
'Contains(101030411): True
'
'weekly(101030411).Description: Motor
'
'Remove(101030411)
'Motor (quantity 10) was Removed.
'
'Insert(2, New OrderItem(...))
'Nut (quantity 10) was Added.
'
'coweekly(2).Description: Nut
'
'coweekly(2) = New OrderItem(...)
'Nut (quantity 10) was replaced by Crank, (quantity 27).
'
'IndexOf(temp): 2
'
'Remove(temp)
'Crank (quantity 27) was Removed.
'
'RemoveAt(0)
'Widget (quantity 400) was Removed.
'
'coweekly(1) = New OrderItem(...)
'Gear (quantity 175) was replaced by Gear, (quantity 1175).
'
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684   1175 Gear         at     5.17 =   6,074.75
'
'The order list was cleared.

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

// This class derives from KeyedCollection and shows how to override
// the protected ClearItems, InsertItem, RemoveItem, and SetItem 
// methods in order to change the behavior of the default Item 
// property and the Add, Clear, Insert, and Remove methods. The
// class implements a Changed event, which is raised by all the
// protected methods.
//
// SimpleOrder is a collection of OrderItem objects, and its key
// is the PartNumber field of OrderItem. PartNumber is an Integer,
// so SimpleOrder inherits KeyedCollection<int, OrderItem>.
// (Note that the key of OrderItem cannot be changed; if it could 
// be changed, SimpleOrder would have to override ChangeItemKey.)
//
public class SimpleOrder : KeyedCollection<int,
 OrderItem>
{
    public event EventHandler<SimpleOrderChangedEventArgs>
 Changed;

    // This parameterless constructor calls the base class constructor
    // that specifies a dictionary threshold of 0, so that the internal
    // dictionary is created as soon as an item is added to the 
    // collection.
    //
    public SimpleOrder() : base(null,
 0) {}
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. 
    //
    protected override int GetKeyForItem(OrderItem
 item)
    {
        // In this example, the key is the part number.
        return item.PartNumber;
    }

    protected override void InsertItem(int
 index, OrderItem newItem)
    {
        base.InsertItem(index, newItem);

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Added, newItem, null));
        }
    }

    protected override void SetItem(int
 index, OrderItem newItem)
    {
        OrderItem replaced = Items[index];
        base.SetItem(index, newItem);

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Replaced, replaced, newItem));
        }
    }

    protected override void RemoveItem(int
 index)
    {
        OrderItem removedItem = Items[index];
        base.RemoveItem(index);

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Removed, removedItem, null));
        }
    }

    protected override void ClearItems()
    {
        base.ClearItems();

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Cleared, null, null));
        }
    }
}

// Event argument for the Changed event.
//
public class SimpleOrderChangedEventArgs :
 EventArgs
{
    private OrderItem _changedItem;
    private ChangeType _changeType;
    private OrderItem _replacedWith;

    public OrderItem ChangedItem { get { return
 _changedItem; }}
    public ChangeType ChangeType { get { return
 _changeType; }}
    public OrderItem ReplacedWith { get { return
 _replacedWith; }}

    public SimpleOrderChangedEventArgs(ChangeType change, 
        OrderItem item, OrderItem replacement)
    {
        _changeType = change;
        _changedItem = item;
        _replacedWith = replacement;
    }
}

public enum ChangeType
{
    Added, 
    Removed, 
    Replaced, 
    Cleared
};

public class Demo
{    
    public static void Main()
    {
        SimpleOrder weekly = new SimpleOrder();
        weekly.Changed += new 
            EventHandler<SimpleOrderChangedEventArgs>(ChangedHandler);

        // The Add method, inherited from Collection, takes OrderItem.
        //
        weekly.Add(new OrderItem(110072674, "Widget",
 400, 45.17));
        weekly.Add(new OrderItem(110072675, "Sprocket",
 27, 5.3));
        weekly.Add(new OrderItem(101030411, "Motor",
 10, 237.5));
        weekly.Add(new OrderItem(110072684, "Gear",
 175, 5.17));

        Display(weekly);
        
        // The Contains method of KeyedCollection takes TKey.
        //
        Console.WriteLine("\nContains(101030411): {0}", 
            weekly.Contains(101030411));

        // The default Item property of KeyedCollection takes the key
        // type, Integer. The property is read-only.
        //
        Console.WriteLine("\nweekly[101030411].Description: {0}", 
            weekly[101030411].Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console.WriteLine("\nRemove(101030411)");
        weekly.Remove(101030411);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console.WriteLine("\nInsert(2, new OrderItem(...))");
        weekly.Insert(2, new OrderItem(111033401, "Nut",
 10, .5));
         
        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem> coweekly = weekly;
        Console.WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2].Description);
 
        Console.WriteLine("\ncoweekly[2] = new OrderItem(...)");
        coweekly[2] = new OrderItem(127700026, "Crank",
 27, 5.98);

        OrderItem temp = coweekly[2];

        // The IndexOf method, inherited from Collection<OrderItem>,
 
        // takes an OrderItem instead of a key.
        // 
        Console.WriteLine("\nIndexOf(temp): {0}", weekly.IndexOf(temp));

        // The inherited Remove method also takes an OrderItem.
        //
        Console.WriteLine("\nRemove(temp)");
        weekly.Remove(temp);

        Console.WriteLine("\nRemoveAt(0)");
        weekly.RemoveAt(0);

        // Increase the quantity for a line item.
        Console.WriteLine("\ncoweekly(1) = New OrderItem(...)");
        coweekly[1] = new OrderItem(coweekly[1].PartNumber, 
            coweekly[1].Description, coweekly[1].Quantity + 1000, 
            coweekly[1].UnitPrice);

        Display(weekly);

        Console.WriteLine();
        weekly.Clear();
    }
    
    private static void
 Display(SimpleOrder order)
    {
        Console.WriteLine();
        foreach( OrderItem item in order )
        {
            Console.WriteLine(item);
        }
    }

    private static void
 ChangedHandler(object source, 
        SimpleOrderChangedEventArgs e)
    {

        OrderItem item = e.ChangedItem;

        if (e.ChangeType==ChangeType.Replaced)
        {
            OrderItem replacement = e.ReplacedWith;

            Console.WriteLine("{0} (quantity {1}) was replaced " +
                "by {2}, (quantity {3}).", item.Description, 
                item.Quantity, replacement.Description, 
                replacement.Quantity);
        }
        else if(e.ChangeType == ChangeType.Cleared)
        {
            Console.WriteLine("The order list was cleared.");
        }
        else
        {
            Console.WriteLine("{0} (quantity {1}) was {2}.", 
                item.Description, item.Quantity, e.ChangeType);
        }
    }
}

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public class OrderItem
{
    private int _partNumber;
    private string _description;
    private double _unitPrice;
    private int _quantity;
    
    public int PartNumber { get
 { return _partNumber; }}
    public string Description { get
 { return _description; }}
    public double UnitPrice { get { return
 _unitPrice; }}
    public int Quantity { get
 { return _quantity; }}
    
    public OrderItem(int partNumber, string
 description, int quantity, 
        double unitPrice)
    {
        _partNumber = partNumber;
        _description = description;
        _quantity = quantity;
        _unitPrice = unitPrice;
    }
    
    public override string ToString()
    {
        return String.Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    }
}

/* This code example produces the following output:

Widget (quantity 400) was Added.
Sprocket (quantity 27) was Added.
Motor (quantity 10) was Added.
Gear (quantity 175) was Added.

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly[101030411].Description: Motor

Remove(101030411)
Motor (quantity 10) was Removed.

Insert(2, new OrderItem(...))
Nut (quantity 10) was Added.

coweekly[2].Description: Nut

coweekly[2] = new OrderItem(...)
Nut (quantity 10) was replaced by Crank, (quantity 27).

IndexOf(temp): 2

Remove(temp)
Crank (quantity 27) was Removed.

RemoveAt(0)
Widget (quantity 400) was Removed.

coweekly(1) = New OrderItem(...)
Gear (quantity 175) was replaced by Gear, (quantity 1175).

110072675     27 Sprocket     at     5.30 =     143.10
110072684   1175 Gear         at     5.17 =   6,074.75

The order list was cleared.
 */

C++

using namespace System;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;

public enum class ChangeTypes
{
    Added,
    Removed, 
    Replaced, 
    Cleared
};

ref class SimpleOrderChangedEventArgs; 

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public ref class OrderItem
{
private:
    int _quantity;

public:
    initonly int PartNumber;
    initonly String^ Description;
    initonly double UnitPrice;
        
    OrderItem(int partNumber, String^ description, int
 quantity, 
        double unitPrice)
    {
        this->PartNumber = partNumber;
        this->Description = description;
        this->Quantity = quantity;
        this->UnitPrice = unitPrice;
    };
    
    property int Quantity    
    {
        int get() { return
 _quantity; };
        void set(int value)
        {
            if (value < 0)
                throw gcnew ArgumentException("Quantity cannot be negative.");
            
            _quantity = value;
        };
    };
        
    virtual String^ ToString() override 
    {
        return String::Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    };
};

// Event argument for the Changed event.
//
public ref class SimpleOrderChangedEventArgs
 : EventArgs
{
public:
    OrderItem^ ChangedItem;
    initonly ChangeTypes ChangeType;
    OrderItem^ ReplacedWith;

    SimpleOrderChangedEventArgs(ChangeTypes change, 
        OrderItem^ item, OrderItem^ replacement)
    {
        this->ChangeType = change;
        this->ChangedItem = item;
        this->ReplacedWith = replacement;
    }
};

// This class derives from KeyedCollection and shows how to override
// the protected ClearItems, InsertItem, RemoveItem, and SetItem 
// methods in order to change the behavior of the default Item 
// property and the Add, Clear, Insert, and Remove methods. The
// class implements a Changed event, which is raised by all the
// protected methods.
//
// SimpleOrder is a collection of OrderItem objects, and its key
// is the PartNumber field of OrderItem-> PartNumber is an Integer
,
// so SimpleOrder inherits KeyedCollection<int, OrderItem>.
// (Note that the key of OrderItem cannot be changed; if it could 
// be changed, SimpleOrder would have to override ChangeItemKey.)
//
public ref class SimpleOrder : KeyedCollection<int,
 OrderItem^>
{
public:
    event EventHandler<SimpleOrderChangedEventArgs^>^ Changed;

    // This parameterless constructor calls the base class constructor
    // that specifies a dictionary threshold of 0, so that the internal
    // dictionary is created as soon as an item is added to the 
    // collection.
    //
    SimpleOrder() : KeyedCollection<int, OrderItem^>(nullptr,
 0) {};
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. 
    //
protected:
    virtual int GetKeyForItem(OrderItem^ item) override
    {
        // In this example, the key is the part number.
        return item->PartNumber;
    }

    virtual void InsertItem(int index, OrderItem^
 newItem) override 
    {
        __super::InsertItem(index, newItem);

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Added, newItem, nullptr));
    }

    virtual void SetItem(int index, OrderItem^
 newItem) override 
    {
        OrderItem^ replaced = this->Items[index];
        __super::SetItem(index, newItem);

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Replaced, replaced, newItem));
    }

    virtual void RemoveItem(int index) override
 
    {
        OrderItem^ removedItem = Items[index];
        __super::RemoveItem(index);

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Removed, removedItem, nullptr));
    }

    virtual void ClearItems() override 
    {
        __super::ClearItems();

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Cleared, nullptr, nullptr));
    }

    // This method uses the internal reference to the dictionary
    // to test fo
public:
    void AddOrMerge(OrderItem^ newItem)
    {

        int key = this->GetKeyForItem(newItem);
        OrderItem^ existingItem = nullptr;

        // The dictionary is not created until the first item is 
        // added, so it is necessary to test for null. Using 
        // AndAlso ensures that TryGetValue is not called if the
        // dictionary does not exist.
        //
        if (this->Dictionary != nullptr
 && 
            this->Dictionary->TryGetValue(key, existingItem))
        {
            existingItem->Quantity += newItem->Quantity;
        }
        else
        {
            this->Add(newItem);
        }
    }
};

public ref class Demo
{    
public:
    static void Main()
    {
        SimpleOrder^ weekly = gcnew SimpleOrder();
        weekly->Changed += gcnew 
            EventHandler<SimpleOrderChangedEventArgs^>(ChangedHandler);

        // The Add method, inherited from Collection, takes OrderItem->
        //
        weekly->Add(gcnew OrderItem(110072674, "Widget", 400, 45.17));
        weekly->Add(gcnew OrderItem(110072675, "Sprocket", 27, 5.3));
        weekly->Add(gcnew OrderItem(101030411, "Motor", 10, 237.5));
        weekly->Add(gcnew OrderItem(110072684, "Gear", 175, 5.17));

        Display(weekly);
        
        // The Contains method of KeyedCollection takes TKey.
        //
        Console::WriteLine("\nContains(101030411): {0}", 
            weekly->Contains(101030411));

        // The default Item property of KeyedCollection takes the key
        // type, Integer. The property is read-only.
        //
        Console::WriteLine("\nweekly[101030411]->Description: {0}",
 
            weekly[101030411]->Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console::WriteLine("\nRemove(101030411)");
        weekly->Remove(101030411);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console::WriteLine("\nInsert(2, gcnew OrderItem(...))");
        weekly->Insert(2, gcnew OrderItem(111033401, "Nut", 10, .5));
         
        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem^>^ coweekly = weekly;
        Console::WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2]->Description);
 
        Console::WriteLine("\ncoweekly[2] = gcnew OrderItem(...)");
        coweekly[2] = gcnew OrderItem(127700026, "Crank", 27, 5.98);

        OrderItem^ temp = coweekly[2];

        // The IndexOf method, inherited from Collection<OrderItem>,
 
        // takes an OrderItem instead of a key.
        // 
        Console::WriteLine("\nIndexOf(temp): {0}", weekly->IndexOf(temp));

        // The inherited Remove method also takes an OrderItem->
        //
        Console::WriteLine("\nRemove(temp)");
        weekly->Remove(temp);

        Console::WriteLine("\nRemoveAt(0)");
        weekly->RemoveAt(0);

        weekly->AddOrMerge(gcnew OrderItem(110072684, "Gear", 1000,
 5.17));

        Display(weekly);

        Console::WriteLine();
        weekly->Clear();
    }
    
private:
    static void Display(SimpleOrder^ order)
    {
        Console::WriteLine();
        for each( OrderItem^ item in order
 )
        {
            Console::WriteLine(item);
        }
    }

    static void ChangedHandler(Object^ source,
 
        SimpleOrderChangedEventArgs^ e)
    {
        OrderItem^ item = e->ChangedItem;

        if (e->ChangeType == ChangeTypes::Replaced)
        {
            OrderItem^ replacement = e->ReplacedWith;

            Console::WriteLine("{0} (quantity {1}) was replaced " +
                "by {2}, (quantity {3}).", item->Description, 
                item->Quantity, replacement->Description, 
                replacement->Quantity);
        }
        else if(e->ChangeType == ChangeTypes::Cleared)
        {
            Console::WriteLine("The order list was cleared.");
        }
        else
        {
            Console::WriteLine("{0} (quantity {1}) was {2}.", 
                item->Description, item->Quantity, e->ChangeType);
        }
    }
};

void main()
{
    Demo::Main();
}

/* This code example produces the following output:

Widget (quantity 400) was Added.
Sprocket (quantity 27) was Added.
Motor (quantity 10) was Added.
Gear (quantity 175) was Added.

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly[101030411]->Description: Motor

Remove(101030411)
Motor (quantity 10) was Removed.

Insert(2, gcnew OrderItem(...))
Nut (quantity 10) was Added.

coweekly[2].Description: Nut

coweekly[2] = gcnew OrderItem(...)
Nut (quantity 10) was replaced by Crank, (quantity 27).

IndexOf(temp): 2

Remove(temp)
Crank (quantity 27) was Removed.

RemoveAt(0)
Widget (quantity 400) was Removed.

110072675     27 Sprocket     at     5.30 =     143.10
110072684   1175 Gear         at     5.17 =   6,074.75

The order list was cleared.
 */

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0
.NET Compact Framework
サポート対象 : 2.0

参照

関連項目
KeyedCollection ジェネリッククラス
KeyedCollection メンバ
System.Collections.ObjectModel 名前空間
IEqualityComparer ジェネリックインターフェイス

KeyedCollection ジェネリッククラス

メモ : このクラスは、.NET Framework version 2.0 で新しく追加されたものです。

キーが値に埋め込まれているコレクションの抽象基本クラスを提供します。

名前空間: System.Collections.ObjectModel
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

<SerializableAttribute> _
<ComVisibleAttribute(False)> _
Public MustInherit Class
 KeyedCollection(Of TKey, TItem)
    Inherits Collection(Of TItem)

Visual Basic (使用法)

Dim instance As KeyedCollection(Of
 TKey, TItem)

[SerializableAttribute] 
[ComVisibleAttribute(false)] 
public abstract class KeyedCollection<TKey,TItem>
 : Collection<TItem>

C++

[SerializableAttribute] 
[ComVisibleAttribute(false)] 
generic<typename TKey, typename TItem>
public ref class KeyedCollection abstract :
 public Collection<TItem>

J# では、ジェネリックな型およびメソッドは使用できますが、新規に宣言することはできません。

JScript

JScript では、ジェネリックな型およびメソッドは使用できません。

型パラメータ

: TKey
コレクション内のキーの型。

: TItem
コレクション内の項目の型。

解説

KeyedCollection クラスでは、O(1) のインデックスによる取得と、O(1) に近いキーによる取得の両方を使用できます。これは抽象型 (Visual Basic の場合は MustInherit) ですが、このクラスの構築ジェネリック型がそれぞれ抽象基本クラスとなるため、より正確には、無数にある抽象型の集合ということもできます。KeyedCollection を使用するには、適切な構築型からコレクション型を派生させます。

KeyedCollection クラスは、IList ジェネリックインターフェイスに基づいたコレクションと IDictionary ジェネリックインターフェイスに基づいたコレクションの両方の特性を備えています。IList ジェネリックインターフェイスに基づいたコレクションと同様に、KeyedCollection も、項目のインデックス付けされたリストです。IDictionary ジェネリックインターフェイスに基づいたコレクションと同様に、KeyedCollection にも各要素に関連付けられたキーがあります。

ディクショナリと異なり、KeyedCollection の要素はキー/値ペアではなく、この場合は、要素全体が値であり、キーはその値内に埋め込まれています。たとえば、KeyedCollection<String,String> (Visual Basic の場合は KeyedCollection(Of String, String)) から派生したコレクションに "John Doe Jr." という要素があるとき、この要素の値が "John Doe Jr."、キーが "Doe" であるような場合が考えられます。また、整数キーを含む従業員レコードのコレクションを KeyedCollection<int,Employee> から派生させることもできます。抽象メソッド GetKeyForItem (Visual Basic の場合は MustOverride) は、キーを要素から抽出します。

既定では、KeyedCollection には検索ディクショナリが含まれます。高速な検索を可能にするため、KeyedCollection に項目が追加されると、項目のキーが 1 度だけ抽出され、検索ディクショナリに保存されます。KeyedCollection を作成する場合、この動作は、ディクショナリ作成のしきい値を指定することによりオーバーライドできます。検索ディクショナリは、要素の数が最初にそのしきい値を超えたときに作成されます。しきい値として –1 を指定した場合、検索ディクショナリは作成されません。既定のディクショナリ作成のしきい値はゼロ (0) です。

メモ
内部検索ディクショナリを使用する場合、このディクショナリには、TItem が参照型のときはコレクションのすべての項目への参照が含まれ、TItem が値型のときはコレクションのすべての項目のコピーが含まれます。したがって、TItem が値型のときに検索ディクショナリを使用するのは適切ではありません。

メモ

内部検索ディクショナリを使用する場合、このディクショナリには、TItem が参照型のときはコレクションのすべての項目への参照が含まれ、TItem が値型のときはコレクションのすべての項目のコピーが含まれます。したがって、TItem が値型のときに検索ディクショナリを使用するのは適切ではありません。

KeyedCollection 内のすべてのキーは一意である必要があります。キーには null 参照 (Visual Basic では Nothing) は使用できません。

使用例

このセクションには、2 つのコード例が含まれています。最初の例は、KeyedCollection から派生させるための必要最小限のコードであり、多数のメソッドを継承しています。2 番目の例は、KeyedCollection のプロテクトメソッドをオーバーライドしてカスタム動作を提供する方法を示しています。

例 1

このコード例は、KeyedCollection からコレクションクラスを派生させるために必要な最小限のコードを示しています。GetKeyForItem メソッドをオーバーライドし、基本クラスコンストラクタに処理を代行させるパブリックコンストラクタを用意しています。また、KeyedCollection クラスおよび Collection クラスから継承されたプロパティおよびメソッドも多数示しています。

Visual Basic

Imports System
Imports System.Collections.Generic
Imports System.Collections.ObjectModel

' This class represents a very simple keyed list of OrderItems,
' inheriting most of its behavior from the KeyedCollection and 
' Collection classes. The immediate base class is the constructed
' type KeyedCollection(Of Integer, OrderItem). When you inherit
' from KeyedCollection, the second generic type argument is the 
' type that you want to store in the collection -- in this case
' OrderItem. The first generic argument is the type that you want
' to use as a key. Its values must be calculated from OrderItem; 
' in this case it is the Integer field PartNumber, so SimpleOrder
' inherits KeyedCollection(Of Integer, OrderItem).
'
Public Class SimpleOrder
    Inherits KeyedCollection(Of Integer,
 OrderItem)

    ' The parameterless constructor of the base class creates a 
    ' KeyedCollection with an internal dictionary. For this code 
    ' example, no other constructors are exposed.
    '
    Public Sub New()
        MyBase.New()
    End Sub
    
    ' This is the only method that absolutely must be overridden,
    ' because without it the KeyedCollection cannot extract the
    ' keys from the items. The input parameter type is the 
    ' second generic type argument, in this case OrderItem, and 
    ' the return value type is the first generic type argument,
    ' in this case Integer.
    '
    Protected Overrides Function
 GetKeyForItem( _
        ByVal item As OrderItem) As
 Integer

        ' In this example, the key is the part number.
        Return item.PartNumber   
    End Function

End Class

Public Class Demo
    
    Public Shared Sub Main()
 
        Dim weekly As New
 SimpleOrder()

        ' The Add method, inherited from Collection, takes OrderItem.
        '
        weekly.Add(New OrderItem(110072674, "Widget",
 400, 45.17))
        weekly.Add(New OrderItem(110072675, "Sprocket",
 27, 5.3))
        weekly.Add(New OrderItem(101030411, "Motor",
 10, 237.5))
        weekly.Add(New OrderItem(110072684, "Gear",
 175, 5.17))
        
        Display(weekly)
    
        ' The Contains method of KeyedCollection takes TKey.
        '
        Console.WriteLine(vbLf & "Contains(101030411): {0}",
 _
            weekly.Contains(101030411))

        ' The default Item property of KeyedCollection takes the key
        ' type, Integer.
        '
        Console.WriteLine(vbLf & "weekly(101030411).Description:
 {0}", _
            weekly(101030411).Description)

        ' The Remove method of KeyedCollection takes a key.
        '
        Console.WriteLine(vbLf & "Remove(101030411)")
        weekly.Remove(101030411)
        Display(weekly)

        ' The Insert method, inherited from Collection, takes an 
        ' index and an OrderItem.
        '
        Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
        weekly.Insert(2, New OrderItem(111033401, "Nut",
 10, .5))
        Display(weekly)

        ' The default Item property is overloaded. One overload comes
        ' from KeyedCollection(Of Integer, OrderItem); that overload
        ' is read-only, and takes Integer because it retrieves by key.
 
        ' The other overload comes from Collection(Of OrderItem), the
 
        ' base class of KeyedCollection(Of Integer, OrderItem); it 
        ' retrieves by index, so it also takes an Integer. The compiler
        ' uses the most-derived overload, from KeyedCollection, so the
        ' only way to access SimpleOrder by index is to cast it to
        ' Collection(Of OrderItem). Otherwise the index is interpreted
        ' as a key, and KeyNotFoundException is thrown.
        '
        Dim coweekly As Collection(Of
 OrderItem) = weekly
        Console.WriteLine(vbLf & "coweekly(2).Description:
 {0}", _
            coweekly(2).Description)
 
        Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
        coweekly(2) = New OrderItem(127700026, "Crank",
 27, 5.98)

        Dim temp As OrderItem = coweekly(2)

        ' The IndexOf method, inherited from Collection(Of OrderItem),
 
        ' takes an OrderItem instead of a key.
        ' 
        Console.WriteLine(vbLf & "IndexOf(temp): {0}",
 _
            weekly.IndexOf(temp))

        ' The inherited Remove method also takes an OrderItem.
        '
        Console.WriteLine(vbLf & "Remove(temp)")
        weekly.Remove(temp)
        Display(weekly)

        Console.WriteLine(vbLf & "RemoveAt(0)")
        weekly.RemoveAt(0)
        Display(weekly)

    End Sub
    
    Private Shared Sub Display(ByVal
 order As SimpleOrder) 
        Console.WriteLine()
        For Each item As
 OrderItem In  order
            Console.WriteLine(item)
        Next item
    End Sub
End Class

' This class represents a simple line item in an order. All the 
' values are immutable except quantity.
' 
Public Class OrderItem
    Public ReadOnly PartNumber As
 Integer
    Public ReadOnly Description As
 String
    Public ReadOnly UnitPrice As
 Double
    
    Private _quantity As Integer
 = 0
    
    Public Sub New(ByVal
 partNumber As Integer, _
                   ByVal description As String,
 _
                   ByVal quantity As Integer,
 _
                   ByVal unitPrice As Double)
 
        Me.PartNumber = partNumber
        Me.Description = description
        Me.Quantity = quantity
        Me.UnitPrice = unitPrice
    End Sub 'New
    
    Public Property Quantity() As
 Integer 
        Get
            Return _quantity
        End Get
        Set
            If value < 0 Then
                Throw New ArgumentException("Quantity
 cannot be negative.")
            End If
            _quantity = value
        End Set
    End Property
        
    Public Overrides Function
 ToString() As String 
        Return String.Format( _
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 _
            PartNumber, _quantity, Description, UnitPrice, _
            UnitPrice * _quantity)
    End Function
End Class

' This code example produces the following output:
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'101030411     10 Motor        at   237.50 =   2,375.00
'110072684    175 Gear         at     5.17 =     904.75
'
'Contains(101030411): True
'
'weekly(101030411).Description: Motor
'
'Remove(101030411)
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684    175 Gear         at     5.17 =     904.75
'
'Insert(2, New OrderItem(...))
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'111033401     10 Nut          at      .50 =       5.00
'110072684    175 Gear         at     5.17 =     904.75
'
'coweekly(2).Description: Nut
'
'coweekly(2) = New OrderItem(...)
'
'IndexOf(temp): 2
'
'Remove(temp)
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684    175 Gear         at     5.17 =     904.75
'
'RemoveAt(0)
'
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684    175 Gear         at     5.17 =     904.75

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

// This class represents a very simple keyed list of OrderItems,
// inheriting most of its behavior from the KeyedCollection and 
// Collection classes. The immediate base class is the constructed
// type KeyedCollection<int, OrderItem>. When you inherit
// from KeyedCollection, the second generic type argument is the 
// type that you want to store in the collection -- in this case
// OrderItem. The first type argument is the type that you want
// to use as a key. Its values must be calculated from OrderItem; 
// in this case it is the int field PartNumber, so SimpleOrder
// inherits KeyedCollection<int, OrderItem>.
//
public class SimpleOrder : KeyedCollection<int,
 OrderItem>
{
    // The parameterless constructor of the base class creates a 
    // KeyedCollection with an internal dictionary. For this code 
    // example, no other constructors are exposed.
    //
    public SimpleOrder() : base() {}
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. The input parameter type is the 
    // second generic type argument, in this case OrderItem, and 
    // the return value type is the first generic type argument,
    // in this case int.
    //
    protected override int GetKeyForItem(OrderItem
 item)
    {
        // In this example, the key is the part number.
        return item.PartNumber;
    }
}

public class Demo
{    
    public static void Main()
    {
        SimpleOrder weekly = new SimpleOrder();

        // The Add method, inherited from Collection, takes OrderItem.
        //
        weekly.Add(new OrderItem(110072674, "Widget",
 400, 45.17));
        weekly.Add(new OrderItem(110072675, "Sprocket",
 27, 5.3));
        weekly.Add(new OrderItem(101030411, "Motor",
 10, 237.5));
        weekly.Add(new OrderItem(110072684, "Gear",
 175, 5.17));
        
        Display(weekly);
    
        // The Contains method of KeyedCollection takes the key, 
        // type, in this case int.
        //
        Console.WriteLine("\nContains(101030411): {0}", 
            weekly.Contains(101030411));

        // The default Item property of KeyedCollection takes a key.
        //
        Console.WriteLine("\nweekly[101030411].Description: {0}", 
            weekly[101030411].Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console.WriteLine("\nRemove(101030411)");
        weekly.Remove(101030411);
        Display(weekly);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console.WriteLine("\nInsert(2, New OrderItem(...))");
        weekly.Insert(2, new OrderItem(111033401, "Nut",
 10, .5));
        Display(weekly);

        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem> coweekly = weekly;
        Console.WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2].Description);
 
        Console.WriteLine("\ncoweekly[2] = new OrderItem(...)");
        coweekly[2] = new OrderItem(127700026, "Crank",
 27, 5.98);

        OrderItem temp = coweekly[2];

        // The IndexOf method inherited from Collection<OrderItem>
 
        // takes an OrderItem instead of a key
        // 
        Console.WriteLine("\nIndexOf(temp): {0}", weekly.IndexOf(temp));

        // The inherited Remove method also takes an OrderItem.
        //
        Console.WriteLine("\nRemove(temp)");
        weekly.Remove(temp);
        Display(weekly);

        Console.WriteLine("\nRemoveAt(0)");
        weekly.RemoveAt(0);
        Display(weekly);

    }
    
    private static void
 Display(SimpleOrder order)
    {
        Console.WriteLine();
        foreach( OrderItem item in order )
        {
            Console.WriteLine(item);
        }
    }
}

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public class OrderItem
{
    public readonly int PartNumber;
    public readonly string Description;
    public readonly double UnitPrice;
    
    private int _quantity = 0;
    
    public OrderItem(int partNumber, string
 description, 
        int quantity, double unitPrice)
    {
        this.PartNumber = partNumber;
        this.Description = description;
        this.Quantity = quantity;
        this.UnitPrice = unitPrice;
    } 
    
    public int Quantity    
    {
        get { return _quantity; }
        set
        {
            if (value<0)
                throw new ArgumentException("Quantity cannot
 be negative.");
            
            _quantity = value;
        }
    }
        
    public override string ToString()
    {
        return String.Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    }
}

/* This code example produces the following output:

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly[101030411].Description: Motor

Remove(101030411)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

Insert(2, New OrderItem(...))

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
111033401     10 Nut          at      .50 =       5.00
110072684    175 Gear         at     5.17 =     904.75

coweekly[2].Description: Nut

coweekly[2] = new OrderItem(...)

IndexOf(temp): 2

Remove(temp)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

RemoveAt(0)

110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75
 */

C++

using namespace System;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public ref class OrderItem
{
private:
    int _quantity;
    
public:
    initonly int PartNumber;
    initonly String^ Description;
    initonly double UnitPrice;
    
    OrderItem(int partNumber, String^ description, 
        int quantity, double unitPrice)
    {
        this->PartNumber = partNumber;
        this->Description = description;
        this->Quantity = quantity;
        this->UnitPrice = unitPrice;
    } 
    
    property int Quantity    
    {
        int get() { return
 _quantity; }
        void set(int value)
        {
            if (value < 0)
                throw gcnew ArgumentException("Quantity cannot be negative.");
            
            _quantity = value;
        }
    }
        
    virtual String^ ToString() override 
    {
        return String::Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    }
};

// This class represents a very simple keyed list of OrderItems,
// inheriting most of its behavior from the KeyedCollection and 
// Collection classes. The immediate base class is the constructed
// type KeyedCollection<int, OrderItem>. When you inherit
// from KeyedCollection, the second generic type argument is the 
// type that you want to store in the collection -- in this case
// OrderItem. The first type argument is the type that you want
// to use as a key. Its values must be calculated from OrderItem; 
// in this case it is the int field PartNumber, so SimpleOrder
// inherits KeyedCollection<int, OrderItem>.
//
public ref class SimpleOrder : KeyedCollection<int,
 OrderItem^>
{
    // The parameterless constructor of the base class creates a 
    // KeyedCollection with an internal dictionary. For this code 
    // example, no other constructors are exposed.
    //
public:
    SimpleOrder() {}
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. The input parameter type is the 
    // second generic type argument, in this case OrderItem, and 
    // the return value type is the first generic type argument,
    // in this case int.
    //
protected:
    virtual int GetKeyForItem(OrderItem^ item) override 
    {
        // In this example, the key is the part number.
        return item->PartNumber;
    }
};

public ref class Demo
{    
public:
    static void Main()
    {
        SimpleOrder^ weekly = gcnew SimpleOrder();

        // The Add method, inherited from Collection, takes OrderItem.
        //
        weekly->Add(gcnew OrderItem(110072674, "Widget", 400, 45.17));
        weekly->Add(gcnew OrderItem(110072675, "Sprocket", 27, 5.3));
        weekly->Add(gcnew OrderItem(101030411, "Motor", 10, 237.5));
        weekly->Add(gcnew OrderItem(110072684, "Gear", 175, 5.17));
        
        Display(weekly);
    
        // The Contains method of KeyedCollection takes the key, 
        // type, in this case int.
        //
        Console::WriteLine("\nContains(101030411): {0}", 
            weekly->Contains(101030411));

        // The default Item property of KeyedCollection takes a key.
        //
        Console::WriteLine("\nweekly(101030411)->Description: {0}",
 
            weekly[101030411]->Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console::WriteLine("\nRemove(101030411)");
        weekly->Remove(101030411);
        Display(weekly);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console::WriteLine("\nInsert(2, New OrderItem(...))");
        weekly->Insert(2, gcnew OrderItem(111033401, "Nut", 10, .5));
        Display(weekly);

        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem^>^ coweekly = weekly;
        Console::WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2]->Description);
 
        Console::WriteLine("\ncoweekly[2] = gcnew OrderItem(...)");
        coweekly[2] = gcnew OrderItem(127700026, "Crank", 27, 5.98);

        OrderItem^ temp = coweekly[2];

        // The IndexOf method inherited from Collection<OrderItem>
 
        // takes an OrderItem instead of a key
        // 
        Console::WriteLine("\nIndexOf(temp): {0}", weekly->IndexOf(temp));

        // The inherited Remove method also takes an OrderItem.
        //
        Console::WriteLine("\nRemove(temp)");
        weekly->Remove(temp);
        Display(weekly);

        Console::WriteLine("\nRemoveAt(0)");
        weekly->RemoveAt(0);
        Display(weekly);

    }
    
private:
    static void Display(SimpleOrder^ order)
    {
        Console::WriteLine();
        for each( OrderItem^ item in order
 )
        {
            Console::WriteLine(item);
        }
    }
};

void main()
{
    Demo::Main();
}

/* This code example produces the following output:

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly(101030411)->Description: Motor

Remove(101030411)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

Insert(2, New OrderItem(...))

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
111033401     10 Nut          at      .50 =       5.00
110072684    175 Gear         at     5.17 =     904.75

coweekly(2)->Description: Nut

coweekly[2] = gcnew OrderItem(...)

IndexOf(temp): 2

Remove(temp)

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75

RemoveAt(0)

110072675     27 Sprocket     at     5.30 =     143.10
110072684    175 Gear         at     5.17 =     904.75
 */

例 2

Demo クラスの Main メソッドで、派生クラスのプロパティおよびメソッドを呼び出すことにより、カスタム動作の例を示します。

このコード例では、変更できないキーを持つオブジェクトを使用します。変更可能なキーを使用するコード例の詳細については、ChangeItemKey のトピックを参照してください。

Visual Basic

Imports System
Imports System.Collections.Generic
Imports System.Collections.ObjectModel

' This class derives from KeyedCollection and shows how to override
' the protected ClearItems, InsertItem, RemoveItem, and SetItem 
' methods in order to change the behavior of the default Item 
' property and the Add, Clear, Insert, and Remove methods. The
' class implements a Changed event, which is raised by all the
' protected methods.
'
' SimpleOrder is a collection of OrderItem objects, and its key
' is the PartNumber field of OrderItem. PartNumber is an Integer,
' so SimpleOrder inherits KeyedCollection(Of Integer, OrderItem).
' (Note that the key of OrderItem cannot be changed; if it could 
' be changed, SimpleOrder would have to override ChangeItemKey.)
'
Public Class SimpleOrder
    Inherits KeyedCollection(Of Integer,
 OrderItem)

    Public Event Changed As
 EventHandler(Of SimpleOrderChangedEventArgs)

    ' This parameterless constructor calls the base class constructor
    ' that specifies a dictionary threshold of 0, so that the internal
    ' dictionary is created as soon as an item is added to the 
    ' collection.
    '
    Public Sub New()
        MyBase.New(Nothing, 0)
    End Sub
    
    ' This is the only method that absolutely must be overridden,
    ' because without it the KeyedCollection cannot extract the
    ' keys from the items. 
    '
    Protected Overrides Function
 GetKeyForItem( _
        ByVal item As OrderItem) As
 Integer

        ' In this example, the key is the part number.
        Return item.PartNumber   
    End Function

    Protected Overrides Sub
 InsertItem( _
        ByVal index As Integer,
 ByVal newItem As OrderItem)

        MyBase.InsertItem(index, newItem)

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Added, newItem, Nothing))
    End Sub

    Protected Overrides Sub
 SetItem(ByVal index As Integer,
 _
        ByVal newItem As OrderItem)

        Dim replaced As OrderItem = Items(index)
        MyBase.SetItem(index, newItem)

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Replaced, replaced, newItem))
    End Sub

    Protected Overrides Sub
 RemoveItem(ByVal index As Integer)

        Dim removedItem As OrderItem = Items(index)
        MyBase.RemoveItem(index)

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Removed, removedItem, Nothing))
    End Sub

    Protected Overrides Sub
 ClearItems()
        MyBase.ClearItems()

        RaiseEvent Changed(Me, New
 SimpleOrderChangedEventArgs( _
            ChangeType.Cleared, Nothing, Nothing))
    End Sub

End Class

' Event argument for the Changed event.
'
Public Class SimpleOrderChangedEventArgs
    Inherits EventArgs

    Private _changedItem As OrderItem
    Private _changeType As ChangeType
    Private _replacedWith As OrderItem

    Public ReadOnly Property
 ChangedItem As OrderItem
        Get
            Return _changedItem
        End Get
    End Property

    Public ReadOnly Property
 ChangeType As ChangeType
        Get
            Return _changeType
        End Get
    End Property

    Public ReadOnly Property
 ReplacedWith As OrderItem
        Get
            Return _replacedWith
        End Get
    End Property

    Public Sub New(ByVal
 change As ChangeType, ByVal item As
 OrderItem, _
        ByVal replacement As OrderItem)

        _changeType = change
        _changedItem = item
        _replacedWith = replacement
    End Sub
End Class

Public Enum ChangeType
    Added
    Removed
    Replaced
    Cleared
End Enum

Public Class Demo
    
    Public Shared Sub Main()
 
        Dim weekly As New
 SimpleOrder()
        AddHandler weekly.Changed, AddressOf
 ChangedHandler

        ' The Add method, inherited from Collection, takes OrderItem.
        '
        weekly.Add(New OrderItem(110072674, "Widget",
 400, 45.17))
        weekly.Add(New OrderItem(110072675, "Sprocket",
 27, 5.3))
        weekly.Add(New OrderItem(101030411, "Motor",
 10, 237.5))
        weekly.Add(New OrderItem(110072684, "Gear",
 175, 5.17))

        Display(weekly)
        
        ' The Contains method of KeyedCollection takes TKey.
        '
        Console.WriteLine(vbLf & "Contains(101030411): {0}",
 _
            weekly.Contains(101030411))

        ' The default Item property of KeyedCollection takes the key
        ' type, Integer. The property is read-only.
        '
        Console.WriteLine(vbLf & "weekly(101030411).Description:
 {0}", _
            weekly(101030411).Description)

        ' The Remove method of KeyedCollection takes a key.
        '
        Console.WriteLine(vbLf & "Remove(101030411)")
        weekly.Remove(101030411)

        ' The Insert method, inherited from Collection, takes an 
        ' index and an OrderItem.
        '
        Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
        weekly.Insert(2, New OrderItem(111033401, "Nut",
 10, .5))
         
        ' The default Item property is overloaded. One overload comes
        ' from KeyedCollection(Of Integer, OrderItem); that overload
        ' is read-only, and takes Integer because it retrieves by key.
 
        ' The other overload comes from Collection(Of OrderItem), the
 
        ' base class of KeyedCollection(Of Integer, OrderItem); it 
        ' retrieves by index, so it also takes an Integer. The compiler
        ' uses the most-derived overload, from KeyedCollection, so the
        ' only way to access SimpleOrder by index is to cast it to
        ' Collection(Of OrderItem). Otherwise the index is interpreted
        ' as a key, and KeyNotFoundException is thrown.
        '
        Dim coweekly As Collection(Of
 OrderItem) = weekly
        Console.WriteLine(vbLf & "coweekly(2).Description:
 {0}", _
            coweekly(2).Description)
 
        Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
        coweekly(2) = New OrderItem(127700026, "Crank",
 27, 5.98)

        Dim temp As OrderItem = coweekly(2)

        ' The IndexOf method, inherited from Collection(Of OrderItem),
 
        ' takes an OrderItem instead of a key.
        ' 
        Console.WriteLine(vbLf & "IndexOf(temp): {0}",
 _
            weekly.IndexOf(temp))

        ' The inherited Remove method also takes an OrderItem.
        '
        Console.WriteLine(vbLf & "Remove(temp)")
        weekly.Remove(temp)

        Console.WriteLine(vbLf & "RemoveAt(0)")
        weekly.RemoveAt(0)

        ' Increase the quantity for a line item.
        Console.WriteLine(vbLf & "coweekly(1) = New OrderItem(...)")
        coweekly(1) = New OrderItem(coweekly(1).PartNumber, _
            coweekly(1).Description, coweekly(1).Quantity + 1000, _
            coweekly(1).UnitPrice)

        Display(weekly)

        Console.WriteLine()
        weekly.Clear()
    End Sub
    
    Private Shared Sub Display(ByVal
 order As SimpleOrder) 
        Console.WriteLine()
        For Each item As
 OrderItem In  order
            Console.WriteLine(item)
        Next item
    End Sub

    Private Shared Sub ChangedHandler(ByVal
 source As Object, _
        ByVal e As SimpleOrderChangedEventArgs)

        Dim item As OrderItem = e.ChangedItem

        If e.ChangeType = ChangeType.Replaced Then
            Dim replacement As OrderItem =
 e.ReplacedWith

            Console.WriteLine("{0} (quantity {1}) was replaced
 " & _
                "by {2}, (quantity {3}).", item.Description,
 _
                item.Quantity, replacement.Description, replacement.Quantity)

        ElseIf e.ChangeType = ChangeType.Cleared Then
            Console.WriteLine("The order list was cleared.")

        Else
            Console.WriteLine("{0} (quantity {1}) was {2}.",
 _
                item.Description, item.Quantity, e.ChangeType)
        End If
    End Sub
End Class

' This class represents a simple line item in an order. All the 
' values are immutable except quantity.
' 
Public Class OrderItem
    
    Private _partNumber As Integer
    Private _description As String
    Private _unitPrice As Double
    Private _quantity As Integer

    Public ReadOnly Property
 PartNumber As Integer
        Get
            Return _partNumber
        End Get
    End Property

    Public ReadOnly Property
 Description As String
        Get
            Return _description
        End Get
    End Property

    Public ReadOnly Property
 UnitPrice As Double
        Get
            Return _unitPrice
        End Get
    End Property
    
    Public ReadOnly Property
 Quantity() As Integer 
        Get
            Return _quantity
        End Get
    End Property
    
    Public Sub New(ByVal
 partNumber As Integer, _
                   ByVal description As String,
 _
                   ByVal quantity As Integer,
 _
                   ByVal unitPrice As Double)
 
        _partNumber = partNumber
        _description = description
        _quantity = quantity
        _unitPrice = unitPrice
    End Sub 'New
        
    Public Overrides Function
 ToString() As String 
        Return String.Format( _
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 _
            PartNumber, _quantity, Description, UnitPrice, _
            UnitPrice * _quantity)
    End Function
End Class

' This code example produces the following output:
'
'Widget (quantity 400) was Added.
'Sprocket (quantity 27) was Added.
'Motor (quantity 10) was Added.
'Gear (quantity 175) was Added.
'
'110072674    400 Widget       at    45.17 =  18,068.00
'110072675     27 Sprocket     at     5.30 =     143.10
'101030411     10 Motor        at   237.50 =   2,375.00
'110072684    175 Gear         at     5.17 =     904.75
'
'Contains(101030411): True
'
'weekly(101030411).Description: Motor
'
'Remove(101030411)
'Motor (quantity 10) was Removed.
'
'Insert(2, New OrderItem(...))
'Nut (quantity 10) was Added.
'
'coweekly(2).Description: Nut
'
'coweekly(2) = New OrderItem(...)
'Nut (quantity 10) was replaced by Crank, (quantity 27).
'
'IndexOf(temp): 2
'
'Remove(temp)
'Crank (quantity 27) was Removed.
'
'RemoveAt(0)
'Widget (quantity 400) was Removed.
'
'coweekly(1) = New OrderItem(...)
'Gear (quantity 175) was replaced by Gear, (quantity 1175).
'
'110072675     27 Sprocket     at     5.30 =     143.10
'110072684   1175 Gear         at     5.17 =   6,074.75
'
'The order list was cleared.

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

// This class derives from KeyedCollection and shows how to override
// the protected ClearItems, InsertItem, RemoveItem, and SetItem 
// methods in order to change the behavior of the default Item 
// property and the Add, Clear, Insert, and Remove methods. The
// class implements a Changed event, which is raised by all the
// protected methods.
//
// SimpleOrder is a collection of OrderItem objects, and its key
// is the PartNumber field of OrderItem. PartNumber is an Integer,
// so SimpleOrder inherits KeyedCollection<int, OrderItem>.
// (Note that the key of OrderItem cannot be changed; if it could 
// be changed, SimpleOrder would have to override ChangeItemKey.)
//
public class SimpleOrder : KeyedCollection<int,
 OrderItem>
{
    public event EventHandler<SimpleOrderChangedEventArgs>
 Changed;

    // This parameterless constructor calls the base class constructor
    // that specifies a dictionary threshold of 0, so that the internal
    // dictionary is created as soon as an item is added to the 
    // collection.
    //
    public SimpleOrder() : base(null,
 0) {}
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. 
    //
    protected override int GetKeyForItem(OrderItem
 item)
    {
        // In this example, the key is the part number.
        return item.PartNumber;
    }

    protected override void InsertItem(int
 index, OrderItem newItem)
    {
        base.InsertItem(index, newItem);

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Added, newItem, null));
        }
    }

    protected override void SetItem(int
 index, OrderItem newItem)
    {
        OrderItem replaced = Items[index];
        base.SetItem(index, newItem);

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Replaced, replaced, newItem));
        }
    }

    protected override void RemoveItem(int
 index)
    {
        OrderItem removedItem = Items[index];
        base.RemoveItem(index);

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Removed, removedItem, null));
        }
    }

    protected override void ClearItems()
    {
        base.ClearItems();

        EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new SimpleOrderChangedEventArgs(
                ChangeType.Cleared, null, null));
        }
    }
}

// Event argument for the Changed event.
//
public class SimpleOrderChangedEventArgs :
 EventArgs
{
    private OrderItem _changedItem;
    private ChangeType _changeType;
    private OrderItem _replacedWith;

    public OrderItem ChangedItem { get { return
 _changedItem; }}
    public ChangeType ChangeType { get { return
 _changeType; }}
    public OrderItem ReplacedWith { get { return
 _replacedWith; }}

    public SimpleOrderChangedEventArgs(ChangeType change, 
        OrderItem item, OrderItem replacement)
    {
        _changeType = change;
        _changedItem = item;
        _replacedWith = replacement;
    }
}

public enum ChangeType
{
    Added, 
    Removed, 
    Replaced, 
    Cleared
};

public class Demo
{    
    public static void Main()
    {
        SimpleOrder weekly = new SimpleOrder();
        weekly.Changed += new 
            EventHandler<SimpleOrderChangedEventArgs>(ChangedHandler);

        // The Add method, inherited from Collection, takes OrderItem.
        //
        weekly.Add(new OrderItem(110072674, "Widget",
 400, 45.17));
        weekly.Add(new OrderItem(110072675, "Sprocket",
 27, 5.3));
        weekly.Add(new OrderItem(101030411, "Motor",
 10, 237.5));
        weekly.Add(new OrderItem(110072684, "Gear",
 175, 5.17));

        Display(weekly);
        
        // The Contains method of KeyedCollection takes TKey.
        //
        Console.WriteLine("\nContains(101030411): {0}", 
            weekly.Contains(101030411));

        // The default Item property of KeyedCollection takes the key
        // type, Integer. The property is read-only.
        //
        Console.WriteLine("\nweekly[101030411].Description: {0}", 
            weekly[101030411].Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console.WriteLine("\nRemove(101030411)");
        weekly.Remove(101030411);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console.WriteLine("\nInsert(2, new OrderItem(...))");
        weekly.Insert(2, new OrderItem(111033401, "Nut",
 10, .5));
         
        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem> coweekly = weekly;
        Console.WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2].Description);
 
        Console.WriteLine("\ncoweekly[2] = new OrderItem(...)");
        coweekly[2] = new OrderItem(127700026, "Crank",
 27, 5.98);

        OrderItem temp = coweekly[2];

        // The IndexOf method, inherited from Collection<OrderItem>,
 
        // takes an OrderItem instead of a key.
        // 
        Console.WriteLine("\nIndexOf(temp): {0}", weekly.IndexOf(temp));

        // The inherited Remove method also takes an OrderItem.
        //
        Console.WriteLine("\nRemove(temp)");
        weekly.Remove(temp);

        Console.WriteLine("\nRemoveAt(0)");
        weekly.RemoveAt(0);

        // Increase the quantity for a line item.
        Console.WriteLine("\ncoweekly(1) = New OrderItem(...)");
        coweekly[1] = new OrderItem(coweekly[1].PartNumber, 
            coweekly[1].Description, coweekly[1].Quantity + 1000, 
            coweekly[1].UnitPrice);

        Display(weekly);

        Console.WriteLine();
        weekly.Clear();
    }
    
    private static void
 Display(SimpleOrder order)
    {
        Console.WriteLine();
        foreach( OrderItem item in order )
        {
            Console.WriteLine(item);
        }
    }

    private static void
 ChangedHandler(object source, 
        SimpleOrderChangedEventArgs e)
    {

        OrderItem item = e.ChangedItem;

        if (e.ChangeType==ChangeType.Replaced)
        {
            OrderItem replacement = e.ReplacedWith;

            Console.WriteLine("{0} (quantity {1}) was replaced " +
                "by {2}, (quantity {3}).", item.Description, 
                item.Quantity, replacement.Description, 
                replacement.Quantity);
        }
        else if(e.ChangeType == ChangeType.Cleared)
        {
            Console.WriteLine("The order list was cleared.");
        }
        else
        {
            Console.WriteLine("{0} (quantity {1}) was {2}.", 
                item.Description, item.Quantity, e.ChangeType);
        }
    }
}

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public class OrderItem
{
    private int _partNumber;
    private string _description;
    private double _unitPrice;
    private int _quantity;
    
    public int PartNumber { get
 { return _partNumber; }}
    public string Description { get
 { return _description; }}
    public double UnitPrice { get { return
 _unitPrice; }}
    public int Quantity { get
 { return _quantity; }}
    
    public OrderItem(int partNumber, string
 description, int quantity, 
        double unitPrice)
    {
        _partNumber = partNumber;
        _description = description;
        _quantity = quantity;
        _unitPrice = unitPrice;
    }
    
    public override string ToString()
    {
        return String.Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    }
}

/* This code example produces the following output:

Widget (quantity 400) was Added.
Sprocket (quantity 27) was Added.
Motor (quantity 10) was Added.
Gear (quantity 175) was Added.

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly[101030411].Description: Motor

Remove(101030411)
Motor (quantity 10) was Removed.

Insert(2, new OrderItem(...))
Nut (quantity 10) was Added.

coweekly[2].Description: Nut

coweekly[2] = new OrderItem(...)
Nut (quantity 10) was replaced by Crank, (quantity 27).

IndexOf(temp): 2

Remove(temp)
Crank (quantity 27) was Removed.

RemoveAt(0)
Widget (quantity 400) was Removed.

coweekly(1) = New OrderItem(...)
Gear (quantity 175) was replaced by Gear, (quantity 1175).

110072675     27 Sprocket     at     5.30 =     143.10
110072684   1175 Gear         at     5.17 =   6,074.75

The order list was cleared.
 */

C++

using namespace System;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;

public enum class ChangeTypes
{
    Added,
    Removed, 
    Replaced, 
    Cleared
};

ref class SimpleOrderChangedEventArgs; 

// This class represents a simple line item in an order. All the 
// values are immutable except quantity.
// 
public ref class OrderItem
{
private:
    int _quantity;

public:
    initonly int PartNumber;
    initonly String^ Description;
    initonly double UnitPrice;
        
    OrderItem(int partNumber, String^ description, int
 quantity, 
        double unitPrice)
    {
        this->PartNumber = partNumber;
        this->Description = description;
        this->Quantity = quantity;
        this->UnitPrice = unitPrice;
    };
    
    property int Quantity    
    {
        int get() { return
 _quantity; };
        void set(int value)
        {
            if (value < 0)
                throw gcnew ArgumentException("Quantity cannot be negative.");
            
            _quantity = value;
        };
    };
        
    virtual String^ ToString() override 
    {
        return String::Format(
            "{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
 
            PartNumber, _quantity, Description, UnitPrice, 
            UnitPrice * _quantity);
    };
};

// Event argument for the Changed event.
//
public ref class SimpleOrderChangedEventArgs
 : EventArgs
{
public:
    OrderItem^ ChangedItem;
    initonly ChangeTypes ChangeType;
    OrderItem^ ReplacedWith;

    SimpleOrderChangedEventArgs(ChangeTypes change, 
        OrderItem^ item, OrderItem^ replacement)
    {
        this->ChangeType = change;
        this->ChangedItem = item;
        this->ReplacedWith = replacement;
    }
};

// This class derives from KeyedCollection and shows how to override
// the protected ClearItems, InsertItem, RemoveItem, and SetItem 
// methods in order to change the behavior of the default Item 
// property and the Add, Clear, Insert, and Remove methods. The
// class implements a Changed event, which is raised by all the
// protected methods.
//
// SimpleOrder is a collection of OrderItem objects, and its key
// is the PartNumber field of OrderItem-> PartNumber is an Integer
,
// so SimpleOrder inherits KeyedCollection<int, OrderItem>.
// (Note that the key of OrderItem cannot be changed; if it could 
// be changed, SimpleOrder would have to override ChangeItemKey.)
//
public ref class SimpleOrder : KeyedCollection<int,
 OrderItem^>
{
public:
    event EventHandler<SimpleOrderChangedEventArgs^>^ Changed;

    // This parameterless constructor calls the base class constructor
    // that specifies a dictionary threshold of 0, so that the internal
    // dictionary is created as soon as an item is added to the 
    // collection.
    //
    SimpleOrder() : KeyedCollection<int, OrderItem^>(nullptr,
 0) {};
    
    // This is the only method that absolutely must be overridden,
    // because without it the KeyedCollection cannot extract the
    // keys from the items. 
    //
protected:
    virtual int GetKeyForItem(OrderItem^ item) override
    {
        // In this example, the key is the part number.
        return item->PartNumber;
    }

    virtual void InsertItem(int index, OrderItem^
 newItem) override 
    {
        __super::InsertItem(index, newItem);

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Added, newItem, nullptr));
    }

    virtual void SetItem(int index, OrderItem^
 newItem) override 
    {
        OrderItem^ replaced = this->Items[index];
        __super::SetItem(index, newItem);

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Replaced, replaced, newItem));
    }

    virtual void RemoveItem(int index) override
 
    {
        OrderItem^ removedItem = Items[index];
        __super::RemoveItem(index);

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Removed, removedItem, nullptr));
    }

    virtual void ClearItems() override 
    {
        __super::ClearItems();

        Changed(this, gcnew SimpleOrderChangedEventArgs(
            ChangeTypes::Cleared, nullptr, nullptr));
    }

    // This method uses the internal reference to the dictionary
    // to test fo
public:
    void AddOrMerge(OrderItem^ newItem)
    {

        int key = this->GetKeyForItem(newItem);
        OrderItem^ existingItem = nullptr;

        // The dictionary is not created until the first item is 
        // added, so it is necessary to test for null. Using 
        // AndAlso ensures that TryGetValue is not called if the
        // dictionary does not exist.
        //
        if (this->Dictionary != nullptr
 && 
            this->Dictionary->TryGetValue(key, existingItem))
        {
            existingItem->Quantity += newItem->Quantity;
        }
        else
        {
            this->Add(newItem);
        }
    }
};

public ref class Demo
{    
public:
    static void Main()
    {
        SimpleOrder^ weekly = gcnew SimpleOrder();
        weekly->Changed += gcnew 
            EventHandler<SimpleOrderChangedEventArgs^>(ChangedHandler);

        // The Add method, inherited from Collection, takes OrderItem->
        //
        weekly->Add(gcnew OrderItem(110072674, "Widget", 400, 45.17));
        weekly->Add(gcnew OrderItem(110072675, "Sprocket", 27, 5.3));
        weekly->Add(gcnew OrderItem(101030411, "Motor", 10, 237.5));
        weekly->Add(gcnew OrderItem(110072684, "Gear", 175, 5.17));

        Display(weekly);
        
        // The Contains method of KeyedCollection takes TKey.
        //
        Console::WriteLine("\nContains(101030411): {0}", 
            weekly->Contains(101030411));

        // The default Item property of KeyedCollection takes the key
        // type, Integer. The property is read-only.
        //
        Console::WriteLine("\nweekly[101030411]->Description: {0}",
 
            weekly[101030411]->Description);

        // The Remove method of KeyedCollection takes a key.
        //
        Console::WriteLine("\nRemove(101030411)");
        weekly->Remove(101030411);

        // The Insert method, inherited from Collection, takes an 
        // index and an OrderItem.
        //
        Console::WriteLine("\nInsert(2, gcnew OrderItem(...))");
        weekly->Insert(2, gcnew OrderItem(111033401, "Nut", 10, .5));
         
        // The default Item property is overloaded. One overload comes
        // from KeyedCollection<int, OrderItem>; that overload
        // is read-only, and takes Integer because it retrieves by key.
 
        // The other overload comes from Collection<OrderItem>,
 the 
        // base class of KeyedCollection<int, OrderItem>; it 
        // retrieves by index, so it also takes an Integer. The compiler
        // uses the most-derived overload, from KeyedCollection, so
 the
        // only way to access SimpleOrder by index is to cast it to
        // Collection<OrderItem>. Otherwise the index is interpreted
        // as a key, and KeyNotFoundException is thrown.
        //
        Collection<OrderItem^>^ coweekly = weekly;
        Console::WriteLine("\ncoweekly[2].Description: {0}", 
            coweekly[2]->Description);
 
        Console::WriteLine("\ncoweekly[2] = gcnew OrderItem(...)");
        coweekly[2] = gcnew OrderItem(127700026, "Crank", 27, 5.98);

        OrderItem^ temp = coweekly[2];

        // The IndexOf method, inherited from Collection<OrderItem>,
 
        // takes an OrderItem instead of a key.
        // 
        Console::WriteLine("\nIndexOf(temp): {0}", weekly->IndexOf(temp));

        // The inherited Remove method also takes an OrderItem->
        //
        Console::WriteLine("\nRemove(temp)");
        weekly->Remove(temp);

        Console::WriteLine("\nRemoveAt(0)");
        weekly->RemoveAt(0);

        weekly->AddOrMerge(gcnew OrderItem(110072684, "Gear", 1000,
 5.17));

        Display(weekly);

        Console::WriteLine();
        weekly->Clear();
    }
    
private:
    static void Display(SimpleOrder^ order)
    {
        Console::WriteLine();
        for each( OrderItem^ item in order
 )
        {
            Console::WriteLine(item);
        }
    }

    static void ChangedHandler(Object^ source,
 
        SimpleOrderChangedEventArgs^ e)
    {
        OrderItem^ item = e->ChangedItem;

        if (e->ChangeType == ChangeTypes::Replaced)
        {
            OrderItem^ replacement = e->ReplacedWith;

            Console::WriteLine("{0} (quantity {1}) was replaced " +
                "by {2}, (quantity {3}).", item->Description, 
                item->Quantity, replacement->Description, 
                replacement->Quantity);
        }
        else if(e->ChangeType == ChangeTypes::Cleared)
        {
            Console::WriteLine("The order list was cleared.");
        }
        else
        {
            Console::WriteLine("{0} (quantity {1}) was {2}.", 
                item->Description, item->Quantity, e->ChangeType);
        }
    }
};

void main()
{
    Demo::Main();
}

/* This code example produces the following output:

Widget (quantity 400) was Added.
Sprocket (quantity 27) was Added.
Motor (quantity 10) was Added.
Gear (quantity 175) was Added.

110072674    400 Widget       at    45.17 =  18,068.00
110072675     27 Sprocket     at     5.30 =     143.10
101030411     10 Motor        at   237.50 =   2,375.00
110072684    175 Gear         at     5.17 =     904.75

Contains(101030411): True

weekly[101030411]->Description: Motor

Remove(101030411)
Motor (quantity 10) was Removed.

Insert(2, gcnew OrderItem(...))
Nut (quantity 10) was Added.

coweekly[2].Description: Nut

coweekly[2] = gcnew OrderItem(...)
Nut (quantity 10) was replaced by Crank, (quantity 27).

IndexOf(temp): 2

Remove(temp)
Crank (quantity 27) was Removed.

RemoveAt(0)
Widget (quantity 400) was Removed.

110072675     27 Sprocket     at     5.30 =     143.10
110072684   1175 Gear         at     5.17 =   6,074.75

The order list was cleared.
 */

継承階層

System.Object
System.Collections.ObjectModel.Collection
System.Collections.ObjectModel.KeyedCollection

スレッドセーフ

この型の public static (Visual Basic では Shared) メンバはすべて、スレッドセーフです。インスタンスメンバの場合は、スレッドセーフであるとは限りません。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0
.NET Compact Framework
サポート対象 : 2.0

参照

関連項目
KeyedCollection メンバ
System.Collections.ObjectModel 名前空間
StringDictionary

KeyedCollection プロパティ

パブリックプロパティパブリックプロパティ

( プロテクトプロパティも参照)

	名前	説明
	Count	Collection に実際に格納されている要素の数を取得します。 ( Collection から継承されます。)
	Item	オーバーロードされます。指定したキーを持つ要素を取得します。

プロテクトプロパティ

	名前	説明
	Items	Collection をラップする List ラッパーを取得します。 ( Collection から継承されます。)

参照

KeyedCollection メソッド

パブリックメソッドパブリックメソッド

( プロテクトメソッドも参照)

	名前	説明
	Add	Collection の末尾にオブジェクトを追加します。 ( Collection から継承されます。)
	Clear	Collection からすべての要素を削除します。 ( Collection から継承されます。)
	Contains	指定したキーの要素がコレクションに含まれているかどうかを確認します。
	CopyTo	Collection 全体を互換性のある 1 次元の Array にコピーします。コピー操作は、コピー先の配列の指定したインデックスから始まります。 ( Collection から継承されます。)
	Equals	オーバーロードされます。 2 つの Object インスタンスが等しいかどうかを判断します。 ( Object から継承されます。)
	GetEnumerator	Collection を反復処理する列挙子を返します。 ( Collection から継承されます。)
	GetHashCode	特定の型のハッシュ関数として機能します。GetHashCode は、ハッシュアルゴリズムや、ハッシュテーブルのようなデータ構造での使用に適しています。 ( Object から継承されます。)
	GetType	現在のインスタンスの Type を取得します。 ( Object から継承されます。)
	IndexOf	指定したオブジェクトを検索し、Collection 全体内で最初に見つかった位置の 0 から始まるインデックスを返します。 ( Collection から継承されます。)
	Insert	Collection 内の指定したインデックスの位置に要素を挿入します。 ( Collection から継承されます。)
	ReferenceEquals	指定した複数の Object インスタンスが同一かどうかを判断します。 ( Object から継承されます。)
	Remove	指定したキーを持つ要素を KeyedCollection から削除します。
	RemoveAt	Collection の指定したインデックスにある要素を削除します。 ( Collection から継承されます。)
	ToString	現在の Object を表す String を返します。 ( Object から継承されます。)

プロテクトメソッド

	名前	説明
	ChangeItemKey	検索ディクショナリの指定した要素に関連付けられたキーを変更します。
	ClearItems	オーバーライドされます。 KeyedCollection からすべての要素を削除します。
	Finalize	Object がガベージコレクションにより収集される前に、その Object がリソースを解放し、その他のクリーンアップ操作を実行できるようにします。 ( Object から継承されます。)
	GetKeyForItem	派生クラスで実装された場合、指定した要素からキーを抽出します。
	InsertItem	オーバーロードされます。 KeyedCollection 内の指定したインデックスの位置に要素を挿入します。
	MemberwiseClone	現在の Object の簡易コピーを作成します。 ( Object から継承されます。)
	RemoveItem	オーバーライドされます。 KeyedCollection の指定したインデックスにある要素を削除します。
	SetItem	オーバーロードされます。指定したインデックス位置の項目を、指定した項目で置き換えます。

参照

KeyedCollection メンバ

キーが値に埋め込まれているコレクションの抽象基本クラスを提供します。

KeyedCollection ジェネリック型で公開されるメンバを以下の表に示します。

プロテクトコンストラクタ

	名前	説明
	KeyedCollection	オーバーロードされます。 KeyedCollection クラスの新しいインスタンスを初期化します。

パブリックプロパティ

( プロテクトプロパティも参照)

	名前	説明
	Count	Collection に実際に格納されている要素の数を取得します。(Collection から継承されます。)
	Item	オーバーロードされます。指定したキーを持つ要素を取得します。

プロテクトプロパティ

	名前	説明
	Items	Collection をラップする List ラッパーを取得します。(Collection から継承されます。)

パブリックメソッド

( プロテクトメソッドも参照)

	名前	説明
	Add	Collection の末尾にオブジェクトを追加します。 (Collection から継承されます。)
	Clear	Collection からすべての要素を削除します。 (Collection から継承されます。)
	Contains	指定したキーの要素がコレクションに含まれているかどうかを確認します。
	CopyTo	Collection 全体を互換性のある 1 次元の Array にコピーします。コピー操作は、コピー先の配列の指定したインデックスから始まります。 (Collection から継承されます。)
	Equals	オーバーロードされます。 2 つの Object インスタンスが等しいかどうかを判断します。 (Object から継承されます。)
	GetEnumerator	Collection を反復処理する列挙子を返します。 (Collection から継承されます。)
	GetHashCode	特定の型のハッシュ関数として機能します。GetHashCode は、ハッシュアルゴリズムや、ハッシュテーブルのようなデータ構造での使用に適しています。 (Object から継承されます。)
	GetType	現在のインスタンスの Type を取得します。 (Object から継承されます。)
	IndexOf	指定したオブジェクトを検索し、Collection 全体内で最初に見つかった位置の 0 から始まるインデックスを返します。 (Collection から継承されます。)
	Insert	Collection 内の指定したインデックスの位置に要素を挿入します。 (Collection から継承されます。)
	ReferenceEquals	指定した複数の Object インスタンスが同一かどうかを判断します。 (Object から継承されます。)
	Remove	指定したキーを持つ要素を KeyedCollection から削除します。
	RemoveAt	Collection の指定したインデックスにある要素を削除します。 (Collection から継承されます。)
	ToString	現在の Object を表す String を返します。 (Object から継承されます。)

プロテクトメソッド

	名前	説明
	ChangeItemKey	検索ディクショナリの指定した要素に関連付けられたキーを変更します。
	ClearItems	オーバーライドされます。 KeyedCollection からすべての要素を削除します。
	Finalize	Object がガベージコレクションにより収集される前に、その Object がリソースを解放し、その他のクリーンアップ操作を実行できるようにします。 (Object から継承されます。)
	GetKeyForItem	派生クラスで実装された場合、指定した要素からキーを抽出します。
	InsertItem	オーバーロードされます。 KeyedCollection 内の指定したインデックスの位置に要素を挿入します。
	MemberwiseClone	現在の Object の簡易コピーを作成します。 (Object から継承されます。)
	RemoveItem	オーバーライドされます。 KeyedCollection の指定したインデックスにある要素を削除します。
	SetItem	オーバーロードされます。指定したインデックス位置の項目を、指定した項目で置き換えます。

参照

KeyedCollectionとは？わかりやすく解説

KeyedCollection コンストラクタ ()

KeyedCollection コンストラクタ

関連項目

KeyedCollection コンストラクタ (ジェネリック IEqualityComparer)

KeyedCollection コンストラクタ (ジェネリック IEqualityComparer, Int32)

KeyedCollection ジェネリッククラス

KeyedCollection プロパティ

関連項目

KeyedCollection メソッド

関連項目

KeyedCollection メンバ

関連項目

「KeyedCollection」の関連用語


	© 2025 Microsoft.All rights reserved.

KeyedCollectionとは？ わかりやすく解説

KeyedCollection コンストラクタ ()

KeyedCollection コンストラクタ

関連項目

KeyedCollection コンストラクタ (ジェネリック IEqualityComparer)

KeyedCollection コンストラクタ (ジェネリック IEqualityComparer, Int32)

KeyedCollection ジェネリック クラス

KeyedCollection プロパティ

関連項目

KeyedCollection メソッド

関連項目

KeyedCollection メンバ

関連項目

急上昇のことば

「KeyedCollection」の関連用語

KeyedCollectionとは？わかりやすく解説

KeyedCollection ジェネリッククラス