KeyedCollection.RemoveItem メソッド
メモ : このメソッドは、.NET Framework version 2.0 で新しく追加されたものです。 KeyedCollection の指定したインデックスにある要素を削除します。
名前空間: System.Collections.ObjectModel
アセンブリ: mscorlib (mscorlib.dll 内)
構文
解説
使用例
プラットフォーム
バージョン情報
参照
アセンブリ: mscorlib (mscorlib.dll 内)
構文解説要素数がディクショナリ作成のしきい値を超えていて、KeyedCollection が検索ディクショナリを使用している場合は、要素数が再度しきい値より低くなっても、検索ディクショナリは継続して使用されます。
このメソッドは O(n) 操作です。ここで、n は Count です。
実装についてのメモ使用例このセクションでは、2 つのコード例により、RemoveItem メソッドをオーバーライドしてコレクションからオブジェクトを削除するカスタム動作を提供する例を示しています。最初の例では、カスタム通知イベントを追加し、2 番目の例では変更可能キーを持つオブジェクトのコレクションへのサポートを提供します。
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、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。
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. */
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. */
このコード例では、ChangeItemKey プロテクト メソッドをオーバーライドして変更可能なキーをサポートする方法、および 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してキーとコレクションの整合性を維持する方法を示します。
KeyedCollection クラスおよび MutableKey クラスから派生した MutableKeys コレクションを作成します。MutableKey クラスには、設定可能な Key プロパティが含まれています。新しいキーをプロパティに割り当てると、プロパティ Set アクセス操作子はコレクションの internal (Visual Basic の場合は Friend) ChangeKey メソッドを呼び出して、新しいキーが既存のキーと競合するかどうかをテストします。競合する場合は例外がスローされ、プロパティ値は変更されません。
MutableKey オブジェクトと MutableKeys コレクションの接続を維持するために、また、オブジェクトが 2 つのコレクションの間に挿入されないようにするために、MutableKey クラスには internal (Visual Basic の場合は Friend) Collection フィールドがあります。このフィールドは、InsertItem メソッドなど、コレクションの項目の追加および削除のためのカスタム動作を提供するプロテクト メソッドによって維持されます。このフィールドは、項目がコレクションに追加されるときに設定され、項目が削除されるときにクリアされます。
Imports System Imports System.Collections.Generic Imports System.Collections.ObjectModel ' This class demonstrates one way to use the ChangeItemKey ' method to store objects with keys that can be changed. The ' ChangeItemKey method is used to keep the internal lookup ' Dictionary in sync with the keys of the stored objects. ' ' MutableKeys stores MutableKey objects, which have an Integer ' Key property that can be set. Therefore, MutableKeys inherits ' KeyedCollection(Of Integer, MutableKey). ' Public Class MutableKeys Inherits KeyedCollection(Of Integer, MutableKey) ' This parameterless constructor delegates to the base class ' constructor that specifies a dictionary threshold. A ' threshold of 0 means the internal Dictionary is created ' the first time an object is added. ' Public Sub New() MyBase.New(Nothing, 0) End Sub Protected Overrides Function GetKeyForItem( _ ByVal item As MutableKey) As Integer ' The key is MutableKey.Key. Return item.Key End Function Protected Overrides Sub InsertItem( _ ByVal index As Integer, ByVal newItem As MutableKey) If newItem.Collection IsNot Nothing Then _ Throw New ArgumentException("The item already belongs to a collection.") MyBase.InsertItem(index, newItem) newItem.Collection = Me End Sub Protected Overrides Sub SetItem(ByVal index As Integer, _ ByVal newItem As MutableKey) Dim replaced As MutableKey = Items(index) If newItem.Collection IsNot Nothing Then _ Throw New ArgumentException("The item already belongs to a collection.") MyBase.SetItem(index, newItem) newItem.Collection = Me replaced.Collection = Nothing End Sub Protected Overrides Sub RemoveItem(ByVal index As Integer) Dim removedItem As MutableKey = Items(index) MyBase.RemoveItem(index) removedItem.Collection = Nothing End Sub Protected Overrides Sub ClearItems() For Each mk As MutableKey In Items mk.Collection = Nothing Next MyBase.ClearItems() End Sub Friend Sub ChangeKey(ByVal item As MutableKey, _ ByVal newKey As Integer) MyBase.ChangeItemKey(item, newKey) End Sub Public Sub Dump() Console.WriteLine(vbLf & "DUMP:") If Dictionary Is Nothing Then Console.WriteLine(" The dictionary has not been created.") Else Console.WriteLine(" Dictionary entries") Console.WriteLine(" ------------------") For Each kvp As KeyValuePair(Of Integer, MutableKey) In Dictionary Console.WriteLine(" {0} : {1}", kvp.Key, kvp.Value) Next End If Console.WriteLine(vbLf & " List of items") Console.WriteLine(" -------------") For Each mk As MutableKey In Items Console.WriteLine(" {0}", mk) Next End Sub End Class Public Class Demo Public Shared Sub Main() Dim mkeys As New MutableKeys() ' The Add method is inherited from Collection. ' mkeys.Add(New MutableKey(110072674, "Widget")) mkeys.Add(New MutableKey(110072675, "Sprocket")) mkeys.Dump() Console.WriteLine(vbLf & "Create and insert a new item:") Dim test As New MutableKey(110072684, "Gear") mkeys.Insert(1, test) mkeys.Dump() Try Console.WriteLine(vbLf & "Try to insert the item again:") mkeys.Insert(1, test) Catch ex As ArgumentException Console.WriteLine("Error: {0}", ex.Message) End Try Console.WriteLine(vbLf & "Change the Key property of the item:") test.Key = 100000072 mkeys.Dump() Try Console.WriteLine(vbLf & "Try to set the Key property to an existing key:") test.Key = 110072674 Catch ex As ArgumentException Console.WriteLine("Error: {0}", ex.Message) End Try mkeys.Dump() End Sub Private Shared Sub Display(ByVal order As MutableKeys) Console.WriteLine() For Each item As MutableKey In order Console.WriteLine(item) Next item End Sub End Class ' This class has a key that can be changed. ' Public Class MutableKey Public Sub New(ByVal newKey As Integer, ByVal newValue As String) _key = newKey Value = newValue End Sub 'New Public Value As String Friend Collection As MutableKeys Private _key As Integer Public Property Key As Integer Get Return _key End Get Set If Collection IsNot Nothing Then Collection.ChangeKey(Me, value) End If _key = value End Set End Property Public Overrides Function ToString() As String Return String.Format("{0,9} {1}", _key, Value) End Function End Class ' This code example produces the following output: ' 'DUMP: ' Dictionary entries ' ------------------ ' 110072674 : 110072674 Widget ' 110072675 : 110072675 Sprocket ' ' List of items ' ------------- ' 110072674 Widget ' 110072675 Sprocket ' 'Create and insert a new item: ' 'DUMP: ' Dictionary entries ' ------------------ ' 110072674 : 110072674 Widget ' 110072675 : 110072675 Sprocket ' 110072684 : 110072684 Gear ' ' List of items ' ------------- ' 110072674 Widget ' 110072684 Gear ' 110072675 Sprocket ' 'Try to insert the item again: 'Error: The item already belongs to a collection. ' 'Change the Key property of the item: ' 'DUMP: ' Dictionary entries ' ------------------ ' 110072674 : 110072674 Widget ' 110072675 : 110072675 Sprocket ' 100000072 : 100000072 Gear ' ' List of items ' ------------- ' 110072674 Widget ' 100000072 Gear ' 110072675 Sprocket ' 'Try to set the Key property to an existing key: 'Error: An item with the same key has already been added. ' 'DUMP: ' Dictionary entries ' ------------------ ' 110072674 : 110072674 Widget ' 110072675 : 110072675 Sprocket ' 100000072 : 100000072 Gear ' ' List of items ' ------------- ' 110072674 Widget ' 100000072 Gear ' 110072675 Sprocket
using System; using System.Collections.Generic; using System.Collections.ObjectModel; // This class demonstrates one way to use the ChangeItemKey // method to store objects with keys that can be changed. The // ChangeItemKey method is used to keep the internal lookup // Dictionary in sync with the keys of the stored objects. // // MutableKeys stores MutableKey objects, which have an Integer // Key property that can be set. Therefore, MutableKeys inherits // KeyedCollection(Of Integer, MutableKey). // public class MutableKeys : KeyedCollection<int, MutableKey> { // This parameterless constructor delegates to the base class // constructor that specifies a dictionary threshold. A // threshold of 0 means the internal Dictionary is created // the first time an object is added. // public MutableKeys() : base(null, 0) {} protected override int GetKeyForItem(MutableKey item) { // The key is MutableKey.Key. return item.Key; } protected override void InsertItem(int index, MutableKey newItem) { if (newItem.Collection != null) throw new ArgumentException("The item already belongs to a collection."); base.InsertItem(index, newItem); newItem.Collection = this; } protected override void SetItem(int index, MutableKey newItem) { MutableKey replaced = Items[index]; if (newItem.Collection != null) throw new ArgumentException("The item already belongs to a collection."); base.SetItem(index, newItem); newItem.Collection = this; replaced.Collection = null; } protected override void RemoveItem(int index) { MutableKey removedItem = Items[index]; base.RemoveItem(index); removedItem.Collection = null; } protected override void ClearItems() { foreach( MutableKey mk in Items ) { mk.Collection = null; } base.ClearItems(); } internal void ChangeKey(MutableKey item, int newKey) { base.ChangeItemKey(item, newKey); } public void Dump() { Console.WriteLine("\nDUMP:"); if (Dictionary == null) { Console.WriteLine(" The dictionary has not been created."); } else { Console.WriteLine(" Dictionary entries"); Console.WriteLine(" ------------------"); foreach( KeyValuePair<int, MutableKey> kvp in Dictionary ) { Console.WriteLine(" {0} : {1}", kvp.Key, kvp.Value); } } Console.WriteLine("\n List of items"); Console.WriteLine(" -------------"); foreach( MutableKey mk in Items ) { Console.WriteLine(" {0}", mk); } } } public class Demo { public static void Main() { MutableKeys mkeys = new MutableKeys(); // The Add method is inherited from Collection. // mkeys.Add(new MutableKey(110072674, "Widget")); mkeys.Add(new MutableKey(110072675, "Sprocket")); mkeys.Dump(); Console.WriteLine("\nCreate and insert a new item:"); MutableKey test = new MutableKey(110072684, "Gear"); mkeys.Insert(1, test); mkeys.Dump(); try { Console.WriteLine("\nTry to insert the item again:"); mkeys.Insert(1, test); } catch(ArgumentException ex) { Console.WriteLine("Error: {0}", ex.Message); } Console.WriteLine("\nChange the Key property of the item:"); test.Key = 100000072; mkeys.Dump(); try { Console.WriteLine("\nTry to set the Key property to an existing key:"); test.Key = 110072674; } catch(ArgumentException ex) { Console.WriteLine("Error: {0}", ex.Message); } mkeys.Dump(); } private static void Display(MutableKeys order) { Console.WriteLine(); foreach( MutableKey item in order ) { Console.WriteLine(item); } } } // This class has a key that can be changed. // public class MutableKey { public MutableKey(int newKey, string newValue) { _key = newKey; Value = newValue; } //New public string Value; internal MutableKeys Collection; private int _key; public int Key { get { return _key; } set { if (Collection != null) { Collection.ChangeKey(this, value); } _key = value; } } public override string ToString() { return String.Format("{0,9} {1}", _key, Value); } } /* This code example produces the following output: DUMP: Dictionary entries ------------------ 110072674 : 110072674 Widget 110072675 : 110072675 Sprocket List of items ------------- 110072674 Widget 110072675 Sprocket Create and insert a new item: DUMP: Dictionary entries ------------------ 110072674 : 110072674 Widget 110072675 : 110072675 Sprocket 110072684 : 110072684 Gear List of items ------------- 110072674 Widget 110072684 Gear 110072675 Sprocket Try to insert the item again: Error: The item already belongs to a collection. Change the Key property of the item: DUMP: Dictionary entries ------------------ 110072674 : 110072674 Widget 110072675 : 110072675 Sprocket 100000072 : 100000072 Gear List of items ------------- 110072674 Widget 100000072 Gear 110072675 Sprocket Try to set the Key property to an existing key: Error: An item with the same key has already been added. DUMP: Dictionary entries ------------------ 110072674 : 110072674 Widget 110072675 : 110072675 Sprocket 100000072 : 100000072 Gear List of items ------------- 110072674 Widget 100000072 Gear 110072675 Sprocket */
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