KeyedCollection<TKey,TItem> コンストラクター

定義

KeyedCollection<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class.

オーバーロード

KeyedCollection<TKey,TItem>()

既定の等値比較子を使用する KeyedCollection<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class that uses the default equality comparer.

KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>)

指定した等値比較子を使用する KeyedCollection<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class that uses the specified equality comparer.

KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32)

指定した等値比較子を使用し、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<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class that uses the specified equality comparer and creates a lookup dictionary when the specified threshold is exceeded.

KeyedCollection<TKey,TItem>()

既定の等値比較子を使用する KeyedCollection<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class that uses the default equality comparer.

protected:
 KeyedCollection();
protected KeyedCollection ();
Protected Sub New ()

このコード例は、KeyedCollection<TKey,TItem>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、基本クラスのコンストラクターにデリゲートするパブリックコンストラクターを提供します。This code example shows the minimum code necessary to derive a collection class from KeyedCollection<TKey,TItem>: overriding the GetKeyForItem method and providing a public constructor that delegates to a base class constructor. このコード例では、KeyedCollection<TKey,TItem> クラスと Collection<T> クラスから継承されたプロパティとメソッドの多くも示しています。The code example also demonstrates many of the properties and methods inherited from KeyedCollection<TKey,TItem> and Collection<T> classes.

SimpleOrder クラスは、OrderItem オブジェクトを含む非常に単純な要求リストです。各オブジェクトは、注文の品目を表します。The SimpleOrder class is a very simple requisition list that contains OrderItem objects, each of which represents a line item in the order. OrderItem のキーは不変であり、KeyedCollection<TKey,TItem>から派生するクラスにとって重要な考慮事項です。The key of OrderItem is immutable, an important consideration for classes that derive from KeyedCollection<TKey,TItem>. 変更可能なキーを使用するコード例については、「ChangeItemKey」を参照してください。For a code example that uses mutable keys, see ChangeItemKey.

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
 */
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>
{
       
    // 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
 */
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)


    ' 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
    
    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

注釈

このコンストラクターで作成された KeyedCollection<TKey,TItem> は、EqualityComparer<T>.Defaultから取得したキーの型に対して既定のジェネリック等値比較子を使用します。A KeyedCollection<TKey,TItem> created with this constructor uses the default generic equality comparer for the type of the key, obtained from EqualityComparer<T>.Default. 別のジェネリック等値比較子を指定するには、KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>) コンストラクターまたは KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) コンストラクターを使用します。To specify a different generic equality comparer, use the KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>) constructor or the KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor.

既定では、KeyedCollection<TKey,TItem> には、最初の項目が追加されたときに作成される検索ディクショナリが含まれます。By default, the KeyedCollection<TKey,TItem> includes a lookup dictionary that is created when the first item is added. 項目が KeyedCollection<TKey,TItem>に追加されると、項目のキーが1回抽出され、検索を高速にするために検索ディクショナリに保存されます。When an item is added to the KeyedCollection<TKey,TItem>, the item's key is extracted once and saved in the lookup dictionary for faster searches. この動作をオーバーライドするには、KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) コンストラクターを使用し、ディクショナリの作成しきい値を指定します。This behavior can be overridden by using the KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor and specifying a dictionary creation threshold.

注意

KeyedCollection<TKey,TItem> クラスは abstract (Visual Basic でMustInherit) であるため、それを使用するためには抽象クラスから派生する必要があります。Because the KeyedCollection<TKey,TItem> class is abstract (MustInherit in Visual Basic), you must derive from it in order to use it. 派生型のコンストラクターで、適切な KeyedCollection<TKey,TItem> コンストラクターを呼び出します。In the constructor for your derived type, call the appropriate KeyedCollection<TKey,TItem> constructor. コンストラクターで、等値比較子やディクショナリ作成のしきい値などの機能を公開する必要はありません。It is not necessary to expose functionality like the equality comparer or the dictionary creation threshold in your constructors.

このコンストラクターは O (1) 操作です。This constructor is an O(1) operation.

こちらもご覧ください

KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>)

指定した等値比較子を使用する KeyedCollection<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class that uses the specified equality comparer.

protected:
 KeyedCollection(System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
protected KeyedCollection (System.Collections.Generic.IEqualityComparer<TKey> comparer);
new System.Collections.ObjectModel.KeyedCollection<'Key, 'Item> : System.Collections.Generic.IEqualityComparer<'Key> -> System.Collections.ObjectModel.KeyedCollection<'Key, 'Item>
Protected Sub New (comparer As IEqualityComparer(Of TKey))

パラメーター

comparer
IEqualityComparer<TKey>

キーを比較する場合に使用する IEqualityComparer<T> ジェネリック インターフェイスの実装。または、Default から取得する、キーの型の既定の等値比較子を使用する場合は nullThe implementation of the IEqualityComparer<T> generic interface to use when comparing keys, or null to use the default equality comparer for the type of the key, obtained from Default.

注釈

既定では、KeyedCollection<TKey,TItem> には、最初の項目が追加されたときに作成される検索ディクショナリが含まれます。By default, the KeyedCollection<TKey,TItem> includes a lookup dictionary that is created when the first item is added. 項目が KeyedCollection<TKey,TItem>に追加されると、項目のキーが1回抽出され、検索を高速にするために検索ディクショナリに保存されます。When an item is added to the KeyedCollection<TKey,TItem>, the item's key is extracted once and saved in the lookup dictionary for faster searches. この動作をオーバーライドするには、KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) コンストラクターを使用し、ディクショナリの作成しきい値を指定します。This behavior can be overridden by using the KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor and specifying a dictionary creation threshold.

注意

KeyedCollection<TKey,TItem> クラスは abstract (Visual Basic でMustInherit) であるため、それを使用するためには抽象クラスから派生する必要があります。Because the KeyedCollection<TKey,TItem> class is abstract (MustInherit in Visual Basic), you must derive from it in order to use it. 派生型のコンストラクターで、適切な KeyedCollection<TKey,TItem> コンストラクターを呼び出します。In the constructor for your derived type, call the appropriate KeyedCollection<TKey,TItem> constructor. コンストラクターで、等値比較子やディクショナリ作成のしきい値などの機能を公開する必要はありません。It is not necessary to expose functionality like the equality comparer or the dictionary creation threshold in your constructors.

このコンストラクターは O (1) 操作です。This constructor is an O(1) operation.

こちらもご覧ください

KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32)

指定した等値比較子を使用し、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<TKey,TItem> クラスの新しいインスタンスを初期化します。Initializes a new instance of the KeyedCollection<TKey,TItem> class that uses the specified equality comparer and creates a lookup dictionary when the specified threshold is exceeded.

protected:
 KeyedCollection(System::Collections::Generic::IEqualityComparer<TKey> ^ comparer, int dictionaryCreationThreshold);
protected KeyedCollection (System.Collections.Generic.IEqualityComparer<TKey> comparer, int dictionaryCreationThreshold);
new System.Collections.ObjectModel.KeyedCollection<'Key, 'Item> : System.Collections.Generic.IEqualityComparer<'Key> * int -> System.Collections.ObjectModel.KeyedCollection<'Key, 'Item>
Protected Sub New (comparer As IEqualityComparer(Of TKey), dictionaryCreationThreshold As Integer)

パラメーター

comparer
IEqualityComparer<TKey>

キーを比較する場合に使用する IEqualityComparer<T> ジェネリック インターフェイスの実装。または、Default から取得する、キーの型の既定の等値比較子を使用する場合は nullThe implementation of the IEqualityComparer<T> generic interface to use when comparing keys, or null to use the default equality comparer for the type of the key, obtained from Default.

dictionaryCreationThreshold
Int32

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。The number of elements the collection can hold without creating a lookup dictionary (0 creates the lookup dictionary when the first item is added), or -1 to specify that a lookup dictionary is never created.

例外

dictionaryCreationThreshold が -1 未満です。dictionaryCreationThreshold is less than -1.

次のコード例は、protected InsertItemRemoveItemClearItems、および SetItem の各メソッドをオーバーライドして、AddRemove、および Clear の各メソッドのカスタム動作を提供し、既定の Item[Int32] プロパティ (のインデクサー) を設定する方法を示しています。C#).The following code example shows how to override the protected InsertItem, RemoveItem, ClearItems, and SetItem methods, to provide custom behavior for the Add, Remove, and Clear methods, and for setting the default Item[Int32] property (the indexer in C#). 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、オーバーライドされた各メソッドの最後に発生します。The custom behavior provided in this example is a notification event named Changed, which is raised at the end of each of the overridden methods.

このコード例では、しきい値が0の KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) コンストラクターを使用して、コレクションにオブジェクトを初めて追加するときに内部ディクショナリが作成されるようにします。The code example uses the KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor with a threshold of 0, so that the internal dictionary is created the first time an object is added to the collection.

このコード例では、KeyedCollection<TKey,TItem> から派生し、単純な注文フォームを表す SimpleOrder クラスを作成します。The code example creates the SimpleOrder class, which derives from KeyedCollection<TKey,TItem> and represents a simple order form. 注文フォームには、注文されたアイテムを表す OrderItem オブジェクトが含まれます。The order form contains OrderItem objects representing items ordered. また、このコード例では、イベント情報を格納する SimpleOrderChangedEventArgs クラスと、変更の種類を識別するための列挙も作成します。The code example also creates a SimpleOrderChangedEventArgs class to contain the event information, and an enumeration to identify the type of change.

このコード例では、Demo クラスの Main メソッドで、派生クラスのプロパティとメソッドを呼び出すことによって、カスタム動作を示します。The code example demonstrates the custom behavior by calling the properties and methods of the derived class, in the Main method of the Demo class.

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。This code example uses objects with immutable keys. 変更可能なキーを使用するコード例については、「ChangeItemKey」を参照してください。For a code example that uses mutable keys, see ChangeItemKey.

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.
 */
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.
 */
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
        
    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.

注釈

既定では、KeyedCollection<TKey,TItem> には、最初の項目が追加されたときに作成される検索ディクショナリが含まれます。By default, the KeyedCollection<TKey,TItem> includes a lookup dictionary that is created when the first item is added. 項目が KeyedCollection<TKey,TItem>に追加されると、項目のキーが1回抽出され、検索を高速にするために検索ディクショナリに保存されます。When an item is added to the KeyedCollection<TKey,TItem>, the item's key is extracted once and saved in the lookup dictionary for faster searches. このコンストラクターを使用すると、その動作をオーバーライドできます。This constructor allows you to override that behavior. 最初の要素が追加されたときにディクショナリを作成するには0を指定し、2番目の要素が追加されたときにディクショナリを作成するには1を指定します。Specify 0 to create the dictionary when the first element is added, 1 to create the dictionary when the second element is added, and so on. しきい値として-1 を指定した場合、検索辞書は作成されません。If you specify -1 as the threshold, the lookup dictionary is never created.

非常に小さなコレクションでは、検索ディクショナリによって提供される取得速度の向上は、辞書に必要な追加メモリには価値がない可能性があります。For very small collections the improvement in retrieval speed provided by the lookup dictionary might not be worth the extra memory required by the dictionary. しきい値を設定すると、そのトレードオフをいつどのようにするかを決めることができます。Setting a threshold allows you to decide when to make that tradeoff.

注意

KeyedCollection<TKey,TItem> クラスは abstract (Visual Basic でMustInherit) であるため、それを使用するためには抽象クラスから派生する必要があります。Because the KeyedCollection<TKey,TItem> class is abstract (MustInherit in Visual Basic), you must derive from it in order to use it. 派生型のコンストラクターで、適切な KeyedCollection<TKey,TItem> コンストラクターを呼び出します。In the constructor for your derived type, call the appropriate KeyedCollection<TKey,TItem> constructor. コンストラクターで、等値比較子やディクショナリ作成のしきい値などの機能を公開する必要はありません。It is not necessary to expose functionality like the equality comparer or the dictionary creation threshold in your constructors.

このコンストラクターは O (1) 操作です。This constructor is an O(1) operation.

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