IEqualityComparer<T> Interface

Definition

generic <typename T>
public interface class IEqualityComparer

public interface IEqualityComparer<in T>

public interface IEqualityComparer<T>

type IEqualityComparer<'T> = interface

Public Interface IEqualityComparer(Of In T)

Public Interface IEqualityComparer(Of T)

Type Parameters

Derived

Microsoft.Extensions.Primitives.StringSegmentComparer

System.StringComparer

System.UriTemplateEquivalenceComparer

System.Collections.Generic.EqualityComparer<T>

System.Collections.Generic.ReferenceEqualityComparer

System.Data.DataRowComparer<TRow>

System.Reflection.Metadata.HandleComparer

System.Xml.Linq.XNodeEqualityComparer

Examples

Im folgenden Beispiel werden einer Wörterbuch Auflistung benutzerdefinierte Box-Objekte hinzugefügt.The following example adds custom Box objects to a dictionary collection. Die Box Objekte werden als gleich betrachtet, wenn ihre Dimensionen identisch sind.The Box objects are considered equal if their dimensions are the same.

using System;
using System.Collections.Generic;

class Example
{
   static void Main()
   {
      BoxEqualityComparer boxEqC = new BoxEqualityComparer();

      var boxes = new Dictionary<Box, string>(boxEqC);

      var redBox = new Box(4, 3, 4);
      AddBox(boxes, redBox, "red");

      var blueBox = new Box(4, 3, 4);
      AddBox(boxes, blueBox, "blue");

      var greenBox = new Box(3, 4, 3);
      AddBox(boxes, greenBox, "green");
      Console.WriteLine();

      Console.WriteLine("The dictionary contains {0} Box objects.",
                        boxes.Count);
   }

   private static void AddBox(Dictionary<Box, String> dict, Box box, String name)
   {
      try {
         dict.Add(box, name);
      }
      catch (ArgumentException e) {
         Console.WriteLine("Unable to add {0}: {1}", box, e.Message);
      }
   }
}

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; }

    public override String ToString()
    {
       return String.Format("({0}, {1}, {2})", Height, Length, Width);
    }
}

class BoxEqualityComparer : IEqualityComparer<Box>
{
    public bool Equals(Box b1, Box b2)
    {
        if (b2 == null && b1 == null)
           return true;
        else if (b1 == null || b2 == null)
           return false;
        else if(b1.Height == b2.Height && b1.Length == b2.Length
                            && b1.Width == b2.Width)
            return true;
        else
            return false;
    }

    public int GetHashCode(Box bx)
    {
        int hCode = bx.Height ^ bx.Length ^ bx.Width;
        return hCode.GetHashCode();
    }
}
// The example displays the following output:
//    Unable to add (4, 3, 4): An item with the same key has already been added.
//
//    The dictionary contains 2 Box objects.

Imports System.Collections.Generic

Module Example
   Public Sub Main()

      Dim boxEqC As New BoxEqualityComparer()

      Dim boxes As New Dictionary(Of Box, String)(boxEqC)

      Dim redBox = New Box(4, 3, 4)
      AddBox(boxes, redBox, "red")

      Dim blueBox = new Box(4, 3, 4)
      AddBox(boxes, blueBox, "blue")

      Dim greenBox = new Box(3, 4, 3)
      AddBox(boxes, greenBox, "green")
      Console.WriteLine()

      Console.WriteLine("The dictionary contains {0} Box objects.",
                        boxes.Count)
   End Sub

   Private Sub AddBox(dict As Dictionary(Of Box, String), box As Box, name As String)
      Try
         dict.Add(box, name)
      Catch e As ArgumentException
         Console.WriteLine("Unable to add {0}: {1}", box, e.Message)
      End Try
   End Sub
End Module

Public Class Box
    Private _Height As Integer
    Private _Length As Integer
    Private _Width As Integer

    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

    Public Property Height() As Integer
        Get
            Return _Height
        End Get
        Set(ByVal value As Integer)
            _Height = value
        End Set
    End Property

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

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

    Public Overrides Function ToString() As String
       Return String.Format("({0}, {1}, {2})", _Height, _Length, _Width)
    End Function
End Class

Class BoxEqualityComparer
    Implements IEqualityComparer(Of Box)

    Public Overloads Function Equals(ByVal b1 As Box, ByVal b2 As Box) _
                   As Boolean Implements IEqualityComparer(Of Box).Equals

        If b1 Is Nothing AndAlso b2 Is Nothing Then
            Return True
        ElseIf b1 Is Nothing Or b2 Is Nothing Then
            Return False
        ElseIf b1.Height = b2.Height AndAlso b1.Length =
                b2.Length AndAlso b1.Width = b2.Width Then
            Return True
        Else
            Return False
        End If
    End Function

    Public Overloads Function GetHashCode(ByVal bx As Box) _
                As Integer Implements IEqualityComparer(Of Box).GetHashCode
        Dim hCode As Integer = bx.Height Xor bx.Length Xor bx.Width
        Return hCode.GetHashCode()
    End Function

End Class
' The example displays the following output:
'    Unable to add (4, 3, 4): An item with the same key has already been added.
'
'    The dictionary contains 2 Box objects.

Remarks

Diese Schnittstelle ermöglicht die Implementierung des angepassten Gleichheits Vergleichs für Auflistungen.This interface allows the implementation of customized equality comparison for collections. Das heißt, Sie können eine eigene Definition der Gleichheit für den Typ Terstellen und angeben, dass diese Definition mit einem Sammlungstyp verwendet werden soll, der die generische IEqualityComparer<T>-Schnittstelle annimmt.That is, you can create your own definition of equality for type T, and specify that this definition be used with a collection type that accepts the IEqualityComparer<T> generic interface. Im .NET Framework akzeptieren Konstruktoren des Dictionary<TKey,TValue> generischen Auflistungs Typs diese Schnittstelle.In the .NET Framework, constructors of the Dictionary<TKey,TValue> generic collection type accept this interface.

Eine Standard Implementierung dieser Schnittstelle wird von der Default-Eigenschaft der generischen Klasse EqualityComparer<T> bereitgestellt.A default implementation of this interface is provided by the Default property of the EqualityComparer<T> generic class. Die StringComparer-Klasse implementiert IEqualityComparer<T> vom Typ String.The StringComparer class implements IEqualityComparer<T> of type String.

Diese Schnittstelle unterstützt nur Gleichheits Vergleiche.This interface supports only equality comparisons. Die Anpassung von vergleichen für Sortierung und Sortierung wird durch die IComparer<T> generische Schnittstelle bereitgestellt.Customization of comparisons for sorting and ordering is provided by the IComparer<T> generic interface.

Es wird empfohlen, dass Sie von der EqualityComparer<T>-Klasse ableiten, anstatt die IEqualityComparer<T>-Schnittstelle zu implementieren, da die EqualityComparer<T>-Klasse mit der IEquatable<T>.Equals-Methode anstelle der Object.Equals-Methode auf Gleichheit prüft.We recommend that you derive from the EqualityComparer<T> class instead of implementing the IEqualityComparer<T> interface, because the EqualityComparer<T> class tests for equality using the IEquatable<T>.Equals method instead of the Object.Equals method. Dies entspricht den Methoden Contains, IndexOf, LastIndexOfund Remove der Dictionary<TKey,TValue>-Klasse und anderer generischer Auflistungen.This is consistent with the Contains, IndexOf, LastIndexOf, and Remove methods of the Dictionary<TKey,TValue> class and other generic collections.

Methods

Applies to

See also

• EqualityComparer<T>
• Dictionary<TKey,TValue>
• Dictionary<TKey,TValue>
• IComparer<T>