通过

KeyedCollection<TKey,TItem>.Dictionary 属性

  • 参考

定义

命名空间:
System.Collections.ObjectModel
程序集:
System.ObjectModel.dll
程序集:
mscorlib.dll
程序集:
netstandard.dll
Source:
KeyedCollection.cs
Source:
KeyedCollection.cs
Source:
KeyedCollection.cs

获取 KeyedCollection<TKey,TItem> 的查找字典。

protected:
 property System::Collections::Generic::IDictionary<TKey, TItem> ^ Dictionary { System::Collections::Generic::IDictionary<TKey, TItem> ^ get(); };
protected System.Collections.Generic.IDictionary<TKey,TItem> Dictionary { get; }
protected System.Collections.Generic.IDictionary<TKey,TItem>? Dictionary { get; }
member this.Dictionary : System.Collections.Generic.IDictionary<'Key, 'Item>
Protected ReadOnly Property Dictionary As IDictionary(Of TKey, TItem)

属性值

IDictionary<TKey,TItem>

KeyedCollection<TKey,TItem> 的查找字典（如果存在），否则为 null。

示例

下面的代码示例演示如何重写受保护的 ChangeItemKey 方法以支持可变键，以及如何重写受保护的 InsertItem、 RemoveItem、 ClearItems和 SetItem 方法来保持键和集合的完整性。

该代码示例创建 MutableKeys 从 派生的 KeyedCollection<TKey,TItem>集合和 MutableKey 类。 类 MutableKey 具有可 Key 设置的属性。 将新键分配给 属性时，属性资源库调用 internal 集合的 Visual Basic) 方法中的 (FriendChangeKey ，以测试新键是否会与现有键冲突。 如果是，则会引发异常，并且不会更改属性值。

为了保持对象与集合之间的连接MutableKey，并防止将对象插入到两个集合中，MutableKey类在 Visual Basic) 字段中具有 (internalFriendCollection。MutableKeys 此字段由受保护的方法维护，这些方法提供用于在集合中添加和删除项的自定义行为，例如 InsertItem 方法。 字段在将项添加到集合时设置，并在删除项时清除。

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

注解

默认情况下， KeyedCollection<TKey,TItem> 包含添加第一项时创建的查找字典。 将项添加到 KeyedCollection<TKey,TItem>时，该项的键将提取一次并保存在查找字典中，以便更快地进行搜索。 可以使用 构造函数并指定字典创建阈值来重写 KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) 此行为。

检索此属性的值的运算复杂度为 O(1)。

适用于

另请参阅