Dictionary.System.Collections.IDictionary.Add メソッドとは何？わかりやすく解説 Weblio辞書

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Dictionary.System.Collections.IDictionary.Add 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。

指定したキーと値をディクショナリに追加します。

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

Visual Basic (宣言)

Private Sub System.Collections.IDictionary.Add
 ( _
    key As Object, _
    value As Object _
) Implements IDictionary.Add

Visual Basic (使用法)

Dim instance As Dictionary(Of
 TKey, TValue)
Dim key As Object
Dim value As Object

CType(instance, IDictionary).Add(key, value)

void IDictionary.Add (
    Object key,
    Object value
)

C++

private:
virtual void System.Collections.IDictionary.Add (
    Object^ key, 
    Object^ value
) sealed = IDictionary::Add

J# では、明示的なインタフェースの実装は使用できますが、新規に宣言することはできません。

JScript

JScript では、明示的なインタフェースの実装は使用できますが、新規に宣言することはできません。

パラメータ

key: キーとして使用するオブジェクト。

value: 値として使用するオブジェクト。

例外

例外の種類	条件
ArgumentNullException	key が null 参照 (Visual Basic では Nothing) です。
ArgumentException	key が、Dictionary のキーの型 TKey に代入できない型です。または value が、Dictionary 内の値の型である TValue に代入できない型です。または同じキーを持つ値が、Dictionary に既に存在します。

例外の種類

条件

ArgumentNullException

key が null 参照 (Visual Basic では Nothing) です。

ArgumentException

key が、Dictionary のキーの型 TKey に代入できない型です。

または

value が、Dictionary 内の値の型である TValue に代入できない型です。

または

同じキーを持つ値が、Dictionary に既に存在します。

解説

Item プロパティを使用すると、ディクショナリ内に存在しないキーの値を設定することで、新しい要素を追加することもできます (例 : myCollection["myNonexistentKey"] = myValue)。ただし、指定したキーがディクショナリに既に存在する場合、Item プロパティを設定すると、既存の値が上書きされます。一方、Add メソッドは、指定したキーが既に存在する場合、例外をスローします。

Count が容量より小さい場合、このメソッドは O(1) 操作に近くなります。新しい要素を格納するために容量を増やす必要がある場合、このメソッドは O(n) 操作になります。ここで、n は Count です。

使用例

System.Collections.IDictionary インターフェイスを使って Dictionary クラスにアクセスする方法を次のコード例に示します。このコード例では、文字列キーを含む文字列の空の Dictionary を作成し、System.Collections.IDictionary.Add メソッドを使用していくつかの要素を追加します。この例では、重複するキーを追加しようとした場合、またはデータ型が適切でないキーや値を指定した場合に、System.Collections.IDictionary.Add メソッドによって ArgumentException がスローされることを示しています。

このコード例では、System.Collections.IDictionary インターフェイスにあるその他いくつかのメンバについても使用方法を示しています。

Visual Basic

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

Public Class Example
    
    Public Shared Sub Main()
 

        ' Create a new dictionary of strings, with string keys,
        ' and access it using the IDictionary interface.
        '
        Dim openWith As IDictionary = _
            New Dictionary(Of String,
 String)
        
        ' Add some elements to the dictionary. There are no 
        ' duplicate keys, but some of the values are duplicates.
        ' IDictionary.Add throws an exception if incorrect types
        ' are supplied for key or value.
        openWith.Add("txt", "notepad.exe")
        openWith.Add("bmp", "paint.exe")
        openWith.Add("dib", "paint.exe")
        openWith.Add("rtf", "wordpad.exe")
        Try
            openWith.Add(42, New Example())
        Catch ex As ArgumentException
            Console.WriteLine("An exception was caught for "
 & _
                "IDictionary.Add. Exception message:"
 & vbLf _
                & vbTab & ex.Message & vbLf)
        End Try
        
        ' The Add method throws an exception if the new key is 
        ' already in the dictionary.
        Try
            openWith.Add("txt", "winword.exe")
        Catch 
            Console.WriteLine("An element with Key = ""txt""
 already exists.")
        End Try

        ' The Item property is the default property, so you 
        ' can omit its name when accessing elements. 
        Console.WriteLine("For key = ""rtf"",
 value = {0}.", _
            openWith("rtf"))
        
        ' The default Item property can be used to change the value
        ' associated with a key.
        openWith("rtf") = "winword.exe"
        Console.WriteLine("For key = ""rtf"",
 value = {0}.", _
            openWith("rtf"))
        
        ' If a key does not exist, setting the default Item property
        ' for that key adds a new key/value pair.
        openWith("doc") = "winword.exe"

        ' The default Item property returns Nothing if the key
        ' is of the wrong data type.
        Console.WriteLine("The default Item property returns Nothing"
 _
            & " if the key is of the wrong type:")
        Console.WriteLine("For key = 2, value = {0}.",
 _
            openWith(2))

        ' The default Item property throws an exception when setting
        ' a value if the key is of the wrong data type.
        Try
            openWith(2) = "This does not get added."
        Catch 
            Console.WriteLine("A key of the wrong type was specified"
 _
                & " when setting the default Item property.")
        End Try

        ' Unlike the default Item property on the Dictionary class
        ' itself, IDictionary.Item does not throw an exception
        ' if the requested key is not in the dictionary.
        Console.WriteLine("For key = ""tif"",
 value = {0}.", _
            openWith("tif"))

        ' Contains can be used to test keys before inserting 
        ' them.
        If Not openWith.Contains("ht")
 Then
            openWith.Add("ht", "hypertrm.exe")
            Console.WriteLine("Value added for key = ""ht"":
 {0}", _
                openWith("ht"))
        End If

        ' IDictionary.Contains returns False if the wrong data 
        ' type is supplied.
        Console.WriteLine("openWith.Contains(29.7) returns {0}",
 _
            openWith.Contains(29.7))

        ' When you use foreach to enumerate dictionary elements
        ' with the IDictionary interface, the elements are retrieved
        ' as DictionaryEntry objects instead of KeyValuePair objects.
        Console.WriteLine()
        For Each de As DictionaryEntry
 In openWith
            Console.WriteLine("Key = {0}, Value = {1}",
 _
                de.Key, de.Value)
        Next 

        ' To get the values alone, use the Values property.
        Dim icoll As ICollection = openWith.Values
        
        ' The elements of the collection are strongly typed
        ' with the type that was specified for dictionary values,
        ' even though the ICollection interface is not strongly
        ' typed.
        Console.WriteLine()
        For Each s As String
 In  icoll
            Console.WriteLine("Value = {0}", s)
        Next s

        ' To get the keys alone, use the Keys property.
        icoll = openWith.Keys
        
        ' The elements of the collection are strongly typed
        ' with the type that was specified for dictionary keys,
        ' even though the ICollection interface is not strongly
        ' typed.
        Console.WriteLine()
        For Each s As String
 In  icoll
            Console.WriteLine("Key = {0}", s)
        Next s

        ' Use the Remove method to remove a key/value pair. No
        ' exception is thrown if the wrong data type is supplied.
        Console.WriteLine(vbLf + "Remove(""dib"")")
        openWith.Remove("dib")
        
        If Not openWith.Contains("dib")
 Then
            Console.WriteLine("Key ""dib""
 is not found.")
        End If

    End Sub

End Class

' This code example produces the following output:
'
'An exception was caught for IDictionary.Add. Exception message:
'        The value "42" is not of type "System.String"
 and cannot be used in this generic collection.
'Parameter name: key
'
'An element with Key = "txt" already exists.
'For key = "rtf", value = wordpad.exe.
'For key = "rtf", value = winword.exe.
'The default Item property returns Nothing if the key is of the wrong
 type:
'For key = 2, value = .
'A key of the wrong type was specified when setting the default Item
 property.
'For key = "tif", value = .
'Value added for key = "ht": hypertrm.exe
'openWith.Contains(29.7) returns False
'
'Key = txt, Value = notepad.exe
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = rtf, Value = winword.exe
'Key = doc, Value = winword.exe
'Key = ht, Value = hypertrm.exe
'
'Value = notepad.exe
'Value = paint.exe
'Value = paint.exe
'Value = winword.exe
'Value = winword.exe
'Value = hypertrm.exe
'
'Key = txt
'Key = bmp
'Key = dib
'Key = rtf
'Key = doc
'Key = ht
'
'Remove("dib")
'Key "dib" is not found.
'

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

public class Example
{
    public static void Main()
    {
        // Create a new dictionary of strings, with string keys,
        // and access it using the IDictionary interface.
        //
        IDictionary openWith = new Dictionary<string,
 string>();

        // Add some elements to the dictionary. There are no 
        // duplicate keys, but some of the values are duplicates.
        // IDictionary.Add throws an exception if incorrect types
        // are supplied for key or value.
        openWith.Add("txt", "notepad.exe");
        openWith.Add("bmp", "paint.exe");
        openWith.Add("dib", "paint.exe");
        openWith.Add("rtf", "wordpad.exe");
        try
        {
            openWith.Add(42, new Example());
        }
        catch (ArgumentException ex)
        {
            Console.WriteLine("An exception was caught for
 " + 
                "IDictionary.Add. Exception message:\n\t{0}\n",
                ex.Message);
        }

        // The Add method throws an exception if the new key is 
        // already in the dictionary.
        try
        {
            openWith.Add("txt", "winword.exe");
        }
        catch (ArgumentException)
        {
            Console.WriteLine("An element with Key = \"txt\" already
 exists.");
        }

        // The Item property is another name for the indexer, so you
 
        // can omit its name when accessing elements. 
        Console.WriteLine("For key = \"rtf\", value = {0}.",
 
            openWith["rtf"]);

        // The indexer can be used to change the value associated
        // with a key.
        openWith["rtf"] = "winword.exe";
        Console.WriteLine("For key = \"rtf\", value = {0}.",
 
            openWith["rtf"]);

        // If a key does not exist, setting the indexer for that key
        // adds a new key/value pair.
        openWith["doc"] = "winword.exe";

        // The indexer returns null if the key is of the wrong data
 
        // type.
        Console.WriteLine("The indexer returns null"
 
            + " if the key is of the wrong type:");
        Console.WriteLine("For key = 2, value = {0}.", 
            openWith[2]);

        // The indexer throws an exception when setting a value
        // if the key is of the wrong data type.
        try
        {
            openWith[2] = "This does not get added.";
        }
        catch (ArgumentException)
        {
            Console.WriteLine("A key of the wrong type was specified" 
                + " when assigning to the indexer.");
        }

        // Unlike the default Item property on the Dictionary class
        // itself, IDictionary.Item does not throw an exception
        // if the requested key is not in the dictionary.
        Console.WriteLine("For key = \"tif\", value = {0}.",
 
            openWith["tif"]);

        // Contains can be used to test keys before inserting 
        // them.
        if (!openWith.Contains("ht"))
        {
            openWith.Add("ht", "hypertrm.exe");
            Console.WriteLine("Value added for key = \"ht\":
 {0}", 
                openWith["ht"]);
        }

        // IDictionary.Contains returns false if the wrong data
        // type is supplied.
        Console.WriteLine("openWith.Contains(29.7) returns {0}",
            openWith.Contains(29.7));

        // When you use foreach to enumerate dictionary elements
        // with the IDictionary interface, the elements are retrieved
        // as DictionaryEntry objects instead of KeyValuePair objects.
        Console.WriteLine();
        foreach( DictionaryEntry de in openWith
 )
        {
            Console.WriteLine("Key = {0}, Value = {1}", 
                de.Key, de.Value);
        }

        // To get the values alone, use the Values property.
        ICollection icoll = openWith.Values;

        // The elements of the collection are strongly typed
        // with the type that was specified for dictionary values,
        // even though the ICollection interface is not strongly
        // typed.
        Console.WriteLine();
        foreach( string s in
 icoll )
        {
            Console.WriteLine("Value = {0}", s);
        }

        // To get the keys alone, use the Keys property.
        icoll = openWith.Keys;

        // The elements of the collection are strongly typed
        // with the type that was specified for dictionary keys,
        // even though the ICollection interface is not strongly
        // typed.
        Console.WriteLine();
        foreach( string s in
 icoll )
        {
            Console.WriteLine("Key = {0}", s);
        }

        // Use the Remove method to remove a key/value pair. No
        // exception is thrown if the wrong data type is supplied.
        Console.WriteLine("\nRemove(\"dib\")");
        openWith.Remove("dib");

        if (!openWith.Contains("dib"))
        {
            Console.WriteLine("Key \"dib\" is not found.");
        }
    }
}

/* This code example produces the following output:

An exception was caught for IDictionary.Add. Exception message:
        The value "42" is not of type "System.String" and cannot
 be used in this generic collection.
Parameter name: key

An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
The indexer returns null if the key is of the
 wrong type:
For key = 2, value = .
A key of the wrong type was specified when assigning to the indexer.
For key = "tif", value = .
Value added for key = "ht": hypertrm.exe
openWith.Contains(29.7) returns False

Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe

Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe

Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht

Remove("dib")
Key "dib" is not found.
 */

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
Dictionary ジェネリッククラス
Dictionary メンバ
System.Collections.Generic 名前空間
IDictionary.Item プロパティ

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Dictionary.System.Collections.IDictionary.Add メソッドとは？ わかりやすく解説

Dictionary.System.Collections.IDictionary.Add メソッド

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Dictionary.System.Collections.IDictionary.Add メソッドとは？わかりやすく解説