EqualityComparer<T> EqualityComparer<T> EqualityComparer<T> EqualityComparer<T> Class

定義

提供基底類別 (Base Class) 用於 IEqualityComparer<T> 泛型介面的實作。Provides a base class for implementations of the IEqualityComparer<T> generic interface.

generic <typename T>
public ref class EqualityComparer abstract : 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
    interface IEqualityComparer<'T>
Public MustInherit Class EqualityComparer(Of T)
Implements IEqualityComparer, IEqualityComparer(Of T)

類型參數

T

要比較之物件的類型。The type of objects to compare.

繼承
EqualityComparer<T>EqualityComparer<T>EqualityComparer<T>EqualityComparer<T>
屬性
實作

範例

下列範例會建立型別之物件的字典集合Box使用相等比較子。The following example creates a dictionary collection of objects of type Box with an equality comparer. 這兩個箱子會被視為相等,如果維度相同的。Two boxes are considered equal if their dimensions are the same. 然後將方塊新增至集合。It then adds the boxes to the collection.

字典會使用不同的方式定義等號比較相等比較子來重新建立:這兩個箱子會被視為相等,如果其磁碟區相同。The dictionary is recreated with an equality comparer that defines equality in a different way: Two boxes are considered equal if their volumes are the same.

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 the following output:
 * 
      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 the following output:
' * 
'    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.
' * 
' 

備註

衍生自這個類別提供的自訂實作IEqualityComparer<T>泛型介面與集合搭配使用這類類別Dictionary<TKey,TValue>泛型類別,或使用這類方法List<T>.SortDerive from this class to provide a custom implementation of the IEqualityComparer<T> generic interface for use with collection classes such as the Dictionary<TKey,TValue> generic class, or with methods such as List<T>.Sort.

Default屬性檢查是否輸入T實作System.IEquatable<T>泛型介面,如果是的話,會傳回EqualityComparer<T>叫用的實作IEquatable<T>.Equals方法。The Default property checks whether type T implements the System.IEquatable<T> generic interface and, if so, returns an EqualityComparer<T> that invokes the implementation of the IEquatable<T>.Equals method. 否則,它會傳回EqualityComparer<T>所提供TOtherwise, it returns an EqualityComparer<T>, as provided by T.

我們建議您衍生自EqualityComparer<T>類別而不是實作IEqualityComparer<T>介面,因為EqualityComparer<T>類別使用等號比較測試IEquatable<T>.Equals方法,而非Object.Equals方法。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. 這是與一致ContainsIndexOfLastIndexOf,以及Remove方法Dictionary<TKey,TValue>類別和其他泛型集合。This is consistent with the Contains, IndexOf, LastIndexOf, and Remove methods of the Dictionary<TKey,TValue> class and other generic collections.

建構函式

EqualityComparer<T>() EqualityComparer<T>() EqualityComparer<T>() EqualityComparer<T>()

初始化 EqualityComparer<T> 類別的新執行個體。Initializes a new instance of the EqualityComparer<T> class.

屬性

Default Default Default Default

傳回泛型引數指定之型別的預設相等比較子 (Comparer)。Returns a default equality comparer for the type specified by the generic argument.

方法

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

判斷指定的物件是否等於目前的物件。Determines whether the specified object is equal to the current object.

(Inherited from Object)
Equals(T, T) Equals(T, T) Equals(T, T) Equals(T, T)

在衍生類別中覆寫時,判斷型別為 T 的兩個物件是否相等。When overridden in a derived class, determines whether two objects of type T are equal.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

做為預設雜湊函式。Serves as the default hash function.

(Inherited from Object)
GetHashCode(T) GetHashCode(T) GetHashCode(T) GetHashCode(T)

在衍生類別中覆寫時,做為雜湊演算法和資料結構之指定物件的雜湊函式,例如雜湊表。When overridden in a derived class, serves as a hash function for the specified object for hashing algorithms and data structures, such as a hash table.

GetType() GetType() GetType() GetType()

取得目前執行個體的 TypeGets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

建立目前 Object 的淺層複製。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

傳回代表目前物件的字串。Returns a string that represents the current object.

(Inherited from Object)

明確介面實作

IEqualityComparer.Equals(Object, Object) IEqualityComparer.Equals(Object, Object) IEqualityComparer.Equals(Object, Object) IEqualityComparer.Equals(Object, Object)

判斷指定的物件是否相等。Determines whether the specified objects are equal.

IEqualityComparer.GetHashCode(Object) IEqualityComparer.GetHashCode(Object) IEqualityComparer.GetHashCode(Object) IEqualityComparer.GetHashCode(Object)

傳回指定物件的雜湊碼。Returns a hash code for the specified object.

適用於

另請參閱