EqualityComparer<T> Klasse

  • Referenz

Definition

Namespace:
System.Collections.Generic
Assembly:
System.Collections.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Quelle:
EqualityComparer.CoreCLR.cs
Quelle:
EqualityComparer.CoreCLR.cs
Quelle:
EqualityComparer.CoreCLR.cs

Stellt eine Basisklasse für Implementierungen der generischen IEqualityComparer<T>-Schnittstelle bereit.

generic <typename T>
public ref class EqualityComparer abstract : System::Collections::Generic::IEqualityComparer<T>, System::Collections::IEqualityComparer
public abstract class EqualityComparer<T> : System.Collections.Generic.IEqualityComparer<T>, System.Collections.IEqualityComparer
[System.Serializable]
public abstract class EqualityComparer<T> : System.Collections.Generic.IEqualityComparer<T>, System.Collections.IEqualityComparer
type EqualityComparer<'T> = class
    interface IEqualityComparer<'T>
    interface IEqualityComparer
[<System.Serializable>]
type EqualityComparer<'T> = class
    interface IEqualityComparer
    interface IEqualityComparer<'T>
Public MustInherit Class EqualityComparer(Of T)
Implements IEqualityComparer, IEqualityComparer(Of T)

Typparameter

T

Der Typ der zu vergleichenden Objekte.

Vererbung
Object
EqualityComparer<T>
Attribute
SerializableAttribute
Implementiert
IEqualityComparer<T> IEqualityComparer

Beispiele

Im folgenden Beispiel wird eine Wörterbuchauflistung von Objekten vom Typ Box mit einem Gleichheitsvergleich erstellt. Zwei Felder gelten als gleich, wenn ihre Abmessungen identisch sind. Anschließend werden die Felder der Auflistung hinzugefügt.

Das Wörterbuch wird mit einem Gleichheitsvergleich neu erstellt, der Gleichheit auf eine andere Weise definiert: Zwei Felder gelten als gleich, wenn ihre Volumes identisch sind.

using System;
using System.Collections.Generic;

class Program
{
    static Dictionary<Box, String> boxes;

    static void Main()
    {
        BoxSameDimensions boxDim = new BoxSameDimensions();
        boxes = new Dictionary<Box, string>(boxDim);

        Console.WriteLine("Boxes equality by dimensions:");
        Box redBox = new Box(8, 4, 8);
        Box greenBox = new Box(8, 6, 8);
        Box blueBox = new Box(8, 4, 8);
        Box yellowBox = new Box(8, 8, 8);
        AddBox(redBox, "red");
        AddBox(greenBox, "green");
        AddBox(blueBox, "blue");
        AddBox(yellowBox, "yellow");

        Console.WriteLine();
        Console.WriteLine("Boxes equality by volume:");

        BoxSameVolume boxVolume = new BoxSameVolume();
        boxes = new Dictionary<Box, string>(boxVolume);
        Box pinkBox = new Box(8, 4, 8);
        Box orangeBox = new Box(8, 6, 8);
        Box purpleBox = new Box(4, 8, 8);
        Box brownBox = new Box(8, 8, 4);
        AddBox(pinkBox, "pink");
        AddBox(orangeBox, "orange");
        AddBox(purpleBox, "purple");
        AddBox(brownBox, "brown");
    }

    public static void AddBox(Box bx, string name)
    {
        try
        {
            boxes.Add(bx, name);
            Console.WriteLine("Added {0}, Count = {1}, HashCode = {2}",
                name, boxes.Count.ToString(), bx.GetHashCode());
        }
        catch (ArgumentException)
        {
            Console.WriteLine("A box equal to {0} is already in the collection.", name);
        }
    }
}

public class Box
{
    public Box(int h, int l, int w)
    {
        this.Height = h;
        this.Length = l;
        this.Width = w;
    }
    public int Height { get; set; }
    public int Length { get; set; }
    public int Width { get; set; }
}

class BoxSameDimensions : EqualityComparer<Box>
{
    public override bool Equals(Box b1, Box b2)
    {
        if (b1 == null && b2 == null)
            return true;
        else if (b1 == null || b2 == null)
            return false;

        return (b1.Height == b2.Height &&
                b1.Length == b2.Length &&
                b1.Width == b2.Width);
    }

    public override int GetHashCode(Box bx)
    {
        int hCode = bx.Height ^ bx.Length ^ bx.Width;
        return hCode.GetHashCode();
    }
}

class BoxSameVolume : EqualityComparer<Box>
{
    public override bool Equals(Box b1, Box b2)
    {
        if (b1 == null && b2 == null)
            return true;
        else if (b1 == null || b2 == null)
            return false;

        return (b1.Height * b1.Width * b1.Length ==
                b2.Height * b2.Width * b2.Length);
    }

    public override int GetHashCode(Box bx)
    {
        int hCode = bx.Height * bx.Length * bx.Width;
        return hCode.GetHashCode();
    }
}
/* This example produces an output similar to the following:
 *
      Boxes equality by dimensions:
      Added red, Count = 1, HashCode = 46104728
      Added green, Count = 2, HashCode = 12289376
      A box equal to blue is already in the collection.
      Added yellow, Count = 3, HashCode = 43495525

      Boxes equality by volume:
      Added pink, Count = 1, HashCode = 55915408
      Added orange, Count = 2, HashCode = 33476626
      A box equal to purple is already in the collection.
      A box equal to brown is already in the collection.
 *
*/

'Imports System.Collections
Imports System.Collections.Generic

Module Program
    Dim boxes As Dictionary(Of Box, [String])

    Public Sub Main(ByVal args As String())

        Dim boxDim As New BoxSameDimensions()
        boxes = New Dictionary(Of Box, String)(boxDim)

        Console.WriteLine("Boxes equality by dimensions:")
        Dim redBox As New Box(8, 4, 8)
        Dim greenBox As New Box(8, 6, 8)
        Dim blueBox As New Box(8, 4, 8)
        Dim yellowBox As New Box(8, 8, 8)
        AddBox(redBox, "red")
        AddBox(greenBox, "green")
        AddBox(blueBox, "blue")
        AddBox(yellowBox, "yellow")

        Console.WriteLine()
        Console.WriteLine("Boxes equality by volume:")

        Dim boxVolume As New BoxSameVolume()
        boxes = New Dictionary(Of Box, String)(boxVolume)
        Dim pinkBox As New Box(8, 4, 8)
        Dim orangeBox As New Box(8, 6, 8)
        Dim purpleBox As New Box(4, 8, 8)
        Dim brownBox As New Box(8, 8, 4)
        AddBox(pinkBox, "pink")
        AddBox(orangeBox, "orange")
        AddBox(purpleBox, "purple")
        AddBox(brownBox, "brown")
    End Sub

    Public Sub AddBox(ByVal bx As Box, ByVal name As String)
        Try
            boxes.Add(bx, name)
            Console.WriteLine("Added {0}, Count = {1}, HashCode = {2}", _
                              name, boxes.Count.ToString(), bx.GetHashCode())
        Catch generatedExceptionName As ArgumentException
            Console.WriteLine("A box equal to {0} is already in the collection.", name)
        End Try
    End Sub
End Module

Public Class Box
    Public Sub New(ByVal h As Integer, ByVal l As Integer, ByVal w As Integer)
        Me.Height = h
        Me.Length = l
        Me.Width = w
    End Sub
    
    Private _Height As Integer
    Public Property Height() As Integer
        Get
            Return _Height
        End Get
        Set(ByVal value As Integer)
            _Height = value
        End Set
    End Property

    Private _Length As Integer
    Public Property Length() As Integer
        Get
            Return _Length
        End Get
        Set(ByVal value As Integer)
            _Length = value
        End Set
    End Property

    Private _Width As Integer
    Public Property Width() As Integer
        Get
            Return _Width
        End Get
        Set(ByVal value As Integer)
            _Width = value
        End Set
    End Property
End Class

Class BoxSameDimensions : Inherits EqualityComparer(Of Box)
    Public Overloads Overrides Function Equals(ByVal b1 As Box, _
                                      ByVal b2 As Box) As Boolean
        If b1 Is Nothing AndAlso b2 Is Nothing Then
           Return True
        Else If b1 Is Nothing OrElse b2 Is Nothing Then
           Return False
        End If

        Return (b1.Height = b2.Height AndAlso b1.Length = b2.Length _
                                      AndAlso b1.Width = b2.Width)
    End Function

    Public Overloads Overrides Function GetHashCode(ByVal bx As Box) As Integer
        Dim hCode As Integer = bx.Height Xor bx.Length Xor bx.Width
        Return hCode.GetHashCode()
    End Function
End Class

Class BoxSameVolume : Inherits EqualityComparer(Of Box)
    Public Overloads Overrides Function Equals(ByVal b1 As Box, _
                                          ByVal b2 As Box) As Boolean
        If b1 Is Nothing AndAlso b2 Is Nothing Then
           Return True
        Else If b1 Is Nothing OrElse b2 Is Nothing Then
           Return False
        End If

        Return (b1.Height * b1.Width * b1.Length = _
                b2.Height * b2.Width * b2.Length)
    End Function

    Public Overloads Overrides Function GetHashCode(ByVal bx As Box) As Integer
        Dim hCode As Integer = bx.Height * bx.Length * bx.Width
        Return hCode.GetHashCode()
    End Function
End Class
' This example produces an output similar to the following:
' * 
'    Boxes equality by dimensions:
'    Added red, Count = 1, HashCode = 46104728
'    Added green, Count = 2, HashCode = 12289376
'    A box equal to blue is already in the collection.
'    Added yellow, Count = 3, HashCode = 43495525
'
'    Boxes equality by volume:
'    Added pink, Count = 1, HashCode = 55915408
'    Added orange, Count = 2, HashCode = 33476626
'    A box equal to purple is already in the collection.
'    A box equal to brown is already in the collection.
' * 
'

Hinweise

Von dieser Klasse ableiten, um eine benutzerdefinierte Implementierung der generischen Schnittstelle für die IEqualityComparer<T> Verwendung mit Auflistungsklassen wie der Dictionary<TKey,TValue> generischen Klasse oder mit Methoden wie List<T>.Sortbereitzustellen.

Die Default -Eigenschaft überprüft, ob der Typ T die System.IEquatable<T> generische Schnittstelle implementiert, und gibt, falls ja, ein EqualityComparer<T> zurück, das die Implementierung der IEquatable<T>.Equals Methode aufruft. Andernfalls wird ein EqualityComparer<T>zurückgegeben, wie von Tbereitgestellt.

In .NET 8 und höheren Versionen wird empfohlen, die EqualityComparer<T>.Create(Func<T,T,Boolean>, Func<T,Int32>) -Methode zum Erstellen von Instanzen dieses Typs zu verwenden.

Konstruktoren

EqualityComparer<T>()

Initialisiert eine neue Instanz der EqualityComparer<T>-Klasse.

Eigenschaften

Default

Gibt für den vom generischen Argument angegebenen Typ einen Standardgleichheitsvergleich zurück.

Methoden

Create(Func<T,T,Boolean>, Func<T,Int32>)

Erstellt ein EqualityComparer<T> , indem die angegebenen Delegaten als Implementierung der Vergleichs Equals(T, T) - und GetHashCode(T) -Methoden verwendet werden.
Equals(Object)

Bestimmt, ob das angegebene Objekt gleich dem aktuellen Objekt ist.

(Geerbt von Object)
Equals(T, T)

Ermittelt beim Überschreiben in einer abgeleiteten Klasse, ob zwei Objekte vom Typ T gleich sind.
GetHashCode()

Fungiert als Standardhashfunktion.

(Geerbt von Object)
GetHashCode(T)

Dient beim Überschreiben in einer abgeleiteten Klasse für das angegebene Objekt als Hashfunktion für Hashalgorithmen und Datenstrukturen wie Hashtabellen.
GetType()

Ruft den Type der aktuellen Instanz ab.

(Geerbt von Object)
MemberwiseClone()

Erstellt eine flache Kopie des aktuellen Object.

(Geerbt von Object)
ToString()

Gibt eine Zeichenfolge zurück, die das aktuelle Objekt darstellt.

(Geerbt von Object)

Explizite Schnittstellenimplementierungen

IEqualityComparer.Equals(Object, Object)

Bestimmt, ob die angegebenen Objekte gleich sind.
IEqualityComparer.GetHashCode(Object)

Gibt einen Hashcode für das angegebene Objekt zurück.

Gilt für:

Weitere Informationen