KeyedCollection<TKey,TItem>.ChangeItemKey(TItem, TKey) メソッド

定義

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。Changes the key associated with the specified element in the lookup dictionary.

protected:
 void ChangeItemKey(TItem item, TKey newKey);
protected void ChangeItemKey (TItem item, TKey newKey);
member this.ChangeItemKey : 'Item * 'Key -> unit
Protected Sub ChangeItemKey (item As TItem, newKey As TKey)

パラメーター

item
TItem

変更するキーの要素。The element to change the key of.

newKey
TKey

item の新しいキー。The new key for item.

例外

itemnull です。item is null.

- または --or- keynull です。key is null.

item が見つかりません。item is not found.

- または --or- keyKeyedCollection<TKey,TItem> に既に存在します。key already exists in the KeyedCollection<TKey,TItem>.

次のコード例は、保護された ChangeItemKey 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、および保護された InsertItemRemoveItemClearItems、および SetItem の各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ています。The following code example shows how to override the protected ChangeItemKey method to support mutable keys, and how to override the protected InsertItem, RemoveItem, ClearItems, and SetItem methods to maintain the integrity of the keys and the collection.

このコード例では、KeyedCollection<TKey,TItem>から派生した MutableKeys コレクションと、MutableKey クラスを作成します。The code example creates the MutableKeys collection, which derives from KeyedCollection<TKey,TItem>, and the MutableKey class. MutableKey クラスには、設定可能な Key プロパティがあります。The MutableKey class has a settable Key property. 新しいキーがプロパティに割り当てられると、プロパティ set アクセス操作子は、コレクションの internal (Visual Basic でFriend ChangeKey) 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。When a new key is assigned to the property, the property setter calls the internal (Friend in Visual Basic) ChangeKey method of the collection to test whether the new key would conflict with an existing key. その場合は、例外がスローされ、プロパティ値は変更されません。If so, an exception is thrown and the property value is not changed.

MutableKey オブジェクトと MutableKeys コレクション間の接続を維持し、オブジェクトが2つのコレクションに挿入されないようにするために、MutableKey クラスにはFriend フィールドに internal (Visual Basic) があります。CollectionIn order to maintain the connection between a MutableKey object and the MutableKeys collection and to prevent an object from being inserted into two collections, the MutableKey class has an internal (Friend in Visual Basic) Collection field. このフィールドは、InsertItem メソッドなどのコレクションの項目を追加および削除するためのカスタム動作を提供する、保護されたメソッドによって管理されます。This field is maintained by the protected methods that provide custom behavior for adding and removing items from the collection, such as the InsertItem method. フィールドは、アイテムがコレクションに追加されたときに設定され、アイテムが削除されるとクリアされます。The field is set when the item is added to a collection and cleared when the item is removed.

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
 */
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
    
    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

注釈

このメソッドは itemに埋め込まれたキーを変更しません。単に、検索ディクショナリに保存されているキーを置き換えます。This method does not modify the key embedded in item; it simply replaces the key saved in the lookup dictionary. したがって、newKeyitemに埋め込まれているキーと異なる場合は、GetKeyForItemによって返されたキーを使用して item にアクセスすることはできません。Therefore, if newKey is different from the key that is embedded in item, you cannot access item by using the key returned by GetKeyForItem.

KeyedCollection<TKey,TItem> にルックアップディクショナリがない場合、このメソッドは何も実行しません。This method does nothing if the KeyedCollection<TKey,TItem> does not have a lookup dictionary.

KeyedCollection<TKey,TItem> 内のすべてのキーは一意である必要があります。Every key in a KeyedCollection<TKey,TItem> must be unique. キーを nullことはできません。A key cannot be null.

このメソッドは、O(1) 操作です。This method is an O(1) operation.

実装に関する注意事項Notes for Implementers

項目に埋め込まれたキーを変更する前に、このメソッドを呼び出して、検索ディクショナリのキーを更新する必要があります。Before modifying the key embedded in an item, you must call this method to update the key in the lookup dictionary. ディクショナリの作成しきい値が-1 の場合、このメソッドを呼び出す必要はありません。If the dictionary creation threshold is -1, calling this method is not necessary.

ChangeItemKey メソッドは、派生クラスのパブリックメソッドとして公開しないでください。Do not expose the ChangeItemKey method as a public method of a derived class. このメソッドを誤用すると、ルックアップディクショナリが項目キーと同期しなくなります。Misuse of this method puts the lookup dictionary out of sync with item keys. たとえば、キーを null に設定してから別の値に設定すると、項目の複数のキーが検索ディクショナリに追加されます。For example, setting the key to null and then setting it to another value adds multiple keys for an item to the lookup dictionary. このメソッドを内部で公開して、変更可能な項目キーを許可します。項目のキーが変更されたときに、このメソッドを使用して、検索ディクショナリのキーを変更します。Expose this method internally to allow mutable item keys: When the key for an item changes, this method is used to change the key in the lookup dictionary.

適用対象

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