Comparer<T> 類別

定義

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

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

類型參數

T

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

繼承
Comparer<T>
屬性
實作

範例

下列範例會從類別衍生類別 BoxLengthFirst Comparer<T>The following example derives a class, BoxLengthFirst, from the Comparer<T> class. 這個比較子會比較兩個型別的物件 BoxThis comparer compares two objects of type Box. 它會先依長度排序,然後依高度和寬度排序。It sorts them first by length, then by height, and then by width. 類別會執行 Box IComparable<T> 介面來控制兩個物件之間的預設比較 BoxThe Box class implements the IComparable<T> interface to control the default comparison between two Box objects. 此預設實值會先依高度排序,然後依長度和寬度排序。This default implementation sorts first by height, then by length, and then by width. 此範例會顯示兩個比較之間的差異,方法是 Box 先使用比較子來排序物件清單 BoxLengthFirst ,然後再使用預設的比較子。The example shows the differences between the two comparisons by sorting a list of Box objects first by using the BoxLengthFirst comparer and then by using the default comparer.

using System;
using System.Collections;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        List<Box> Boxes = new List<Box>();
        Boxes.Add(new Box(4, 20, 14));
        Boxes.Add(new Box(12, 12, 12));
        Boxes.Add(new Box(8, 20, 10));
        Boxes.Add(new Box(6, 10, 2));
        Boxes.Add(new Box(2, 8, 4));
        Boxes.Add(new Box(2, 6, 8));
        Boxes.Add(new Box(4, 12, 20));
        Boxes.Add(new Box(18, 10, 4));
        Boxes.Add(new Box(24, 4, 18));
        Boxes.Add(new Box(10, 4, 16));
        Boxes.Add(new Box(10, 2, 10));
        Boxes.Add(new Box(6, 18, 2));
        Boxes.Add(new Box(8, 12, 4));
        Boxes.Add(new Box(12, 10, 8));
        Boxes.Add(new Box(14, 6, 6));
        Boxes.Add(new Box(16, 6, 16));
        Boxes.Add(new Box(2, 8, 12));
        Boxes.Add(new Box(4, 24, 8));
        Boxes.Add(new Box(8, 6, 20));
        Boxes.Add(new Box(18, 18, 12));

        // Sort by an Comparer<T> implementation that sorts
        // first by the length.
        Boxes.Sort(new BoxLengthFirst());

        Console.WriteLine("H - L - W");
        Console.WriteLine("==========");
        foreach (Box bx in Boxes)
        {
            Console.WriteLine("{0}\t{1}\t{2}",
                bx.Height.ToString(), bx.Length.ToString(),
                bx.Width.ToString());
        }

        Console.WriteLine();
        Console.WriteLine("H - L - W");
        Console.WriteLine("==========");

        // Get the default comparer that
        // sorts first by the height.
        Comparer<Box> defComp = Comparer<Box>.Default;

        // Calling Boxes.Sort() with no parameter
        // is the same as calling Boxs.Sort(defComp)
        // because they are both using the default comparer.
        Boxes.Sort();

        foreach (Box bx in Boxes)
        {
            Console.WriteLine("{0}\t{1}\t{2}",
                bx.Height.ToString(), bx.Length.ToString(),
                bx.Width.ToString());
        }


        // This explicit interface implementation
        // compares first by the length.
        // Returns -1 because the length of BoxA
        // is less than the length of BoxB.
        BoxLengthFirst LengthFirst = new BoxLengthFirst();

        Comparer<Box> bc = (Comparer<Box>) LengthFirst;

        Box BoxA = new Box(2, 6, 8);
        Box BoxB = new Box(10, 12, 14);
        int x = LengthFirst.Compare(BoxA, BoxB);
        Console.WriteLine();
        Console.WriteLine(x.ToString());
    }
}

public class BoxLengthFirst : Comparer<Box>
{
    // Compares by Length, Height, and Width.
    public override int Compare(Box x, Box y)
    {
        if (x.Length.CompareTo(y.Length) != 0)
        {
            return x.Length.CompareTo(y.Length);
        }
        else if (x.Height.CompareTo(y.Height) != 0)
        {
            return x.Height.CompareTo(y.Height);
        }
        else if (x.Width.CompareTo(y.Width) != 0)
        {
            return x.Width.CompareTo(y.Width);
        }
        else
        {
            return 0;
        }
    }
}

// This class is not demonstrated in the Main method
// and is provided only to show how to implement
// the interface. It is recommended to derive
// from Comparer<T> instead of implementing IComparer<T>.
public class BoxComp : IComparer<Box>
{
    // Compares by Height, Length, and Width.
    public int Compare(Box x, Box y)
    {
        if (x.Height.CompareTo(y.Height) != 0)
        {
            return x.Height.CompareTo(y.Height);
        }
        else if (x.Length.CompareTo(y.Length) != 0)
        {
            return x.Length.CompareTo(y.Length);
        }
        else if (x.Width.CompareTo(y.Width) != 0)
        {
            return x.Width.CompareTo(y.Width);
        }
        else
        {
            return 0;
        }
    }
}

public class Box : IComparable<Box>
{

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

    public int CompareTo(Box other)
    {
        // Compares Height, Length, and Width.
        if (this.Height.CompareTo(other.Height) != 0)
        {
            return this.Height.CompareTo(other.Height);
        }
        else if (this.Length.CompareTo(other.Length) != 0)
        {
            return this.Length.CompareTo(other.Length);
        }
        else if (this.Width.CompareTo(other.Width) != 0)
        {
            return this.Width.CompareTo(other.Width);
        }
        else
        {
            return 0;
        }
    }
}
Imports System.Collections.Generic

Friend Class Program
    Shared Sub Main(ByVal args() As String)
        Dim Boxes As New List(Of Box)()
        Boxes.Add(New Box(4, 20, 14))
        Boxes.Add(New Box(12, 12, 12))
        Boxes.Add(New Box(8, 20, 10))
        Boxes.Add(New Box(6, 10, 2))
        Boxes.Add(New Box(2, 8, 4))
        Boxes.Add(New Box(2, 6, 8))
        Boxes.Add(New Box(4, 12, 20))
        Boxes.Add(New Box(18, 10, 4))
        Boxes.Add(New Box(24, 4, 18))
        Boxes.Add(New Box(10, 4, 16))
        Boxes.Add(New Box(10, 2, 10))
        Boxes.Add(New Box(6, 18, 2))
        Boxes.Add(New Box(8, 12, 4))
        Boxes.Add(New Box(12, 10, 8))
        Boxes.Add(New Box(14, 6, 6))
        Boxes.Add(New Box(16, 6, 16))
        Boxes.Add(New Box(2, 8, 12))
        Boxes.Add(New Box(4, 24, 8))
        Boxes.Add(New Box(8, 6, 20))
        Boxes.Add(New Box(18, 18, 12))

        ' Sort by an Comparer<T> implementation that sorts
        ' first by the length.
        Boxes.Sort(New BoxLengthFirst())

        Console.WriteLine("H - L - W")
        Console.WriteLine("==========")
        For Each bx As Box In Boxes
            Console.WriteLine("{0}" & vbTab & "{1}" & vbTab & "{2}", _
                              bx.Height.ToString(), bx.Length.ToString(), _
                              bx.Width.ToString())
        Next bx

        Console.WriteLine()
        Console.WriteLine("H - L - W")
        Console.WriteLine("==========")

        ' Get the default comparer that 
        ' sorts first by the height.
        Dim defComp As Comparer(Of Box) = Comparer(Of Box).Default

        ' Calling Boxes.Sort() with no parameter
        ' is the same as calling Boxs.Sort(defComp)
        ' because they are both using the default comparer.
        Boxes.Sort()

        For Each bx As Box In Boxes
            Console.WriteLine("{0}" & vbTab & "{1}" & vbTab & "{2}", _
                              bx.Height.ToString(), _
                              bx.Length.ToString(), _
                              bx.Width.ToString())
        Next bx


        ' This explicit interface implementation
        ' compares first by the length.
        ' Returns -1 because the length of BoxA
        ' is less than the length of BoxB.
        Dim LengthFirst As New BoxLengthFirst()

        Dim bc As Comparer(Of Box) = CType(LengthFirst, Comparer(Of Box))

        Dim BoxA As New Box(2, 6, 8)
        Dim BoxB As New Box(10, 12, 14)
        Dim x As Integer = LengthFirst.Compare(BoxA, BoxB)
        Console.WriteLine()
        Console.WriteLine(x.ToString())



    End Sub

End Class

Public Class BoxLengthFirst
    Inherits Comparer(Of Box)
    ' Compares by Length, Height, and Width.
    Public Overrides Function Compare(ByVal x As Box, ByVal y As Box) As Integer
        If x.Length.CompareTo(y.Length) <> 0 Then
            Return x.Length.CompareTo(y.Length)
        ElseIf x.Height.CompareTo(y.Height) <> 0 Then
            Return x.Height.CompareTo(y.Height)
        ElseIf x.Width.CompareTo(y.Width) <> 0 Then
            Return x.Width.CompareTo(y.Width)
        Else
            Return 0
        End If
    End Function

End Class

' This class is not demonstrated in the Main method
' and is provided only to show how to implement
' the interface. It is recommended to derive
' from Comparer<T> instead of implementing IComparer<T>.
Public Class BoxComp
    Implements IComparer(Of Box)
    ' Compares by Height, Length, and Width.
    Public Function Compare(ByVal x As Box, ByVal y As Box) As Integer Implements _
                                                IComparer(Of Box).Compare
        If x.Height.CompareTo(y.Height) <> 0 Then
            Return x.Height.CompareTo(y.Height)
        ElseIf x.Length.CompareTo(y.Length) <> 0 Then
            Return x.Length.CompareTo(y.Length)
        ElseIf x.Width.CompareTo(y.Width) <> 0 Then
            Return x.Width.CompareTo(y.Width)
        Else
            Return 0
        End If
    End Function
End Class

Public Class Box
    Implements IComparable(Of 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 privateHeight As Integer
    Public Property Height() As Integer
        Get
            Return privateHeight
        End Get
        Private Set(ByVal value As Integer)
            privateHeight = value
        End Set
    End Property
    Private privateLength As Integer
    Public Property Length() As Integer
        Get
            Return privateLength
        End Get
        Private Set(ByVal value As Integer)
            privateLength = value
        End Set
    End Property
    Private privateWidth As Integer
    Public Property Width() As Integer
        Get
            Return privateWidth
        End Get
        Private Set(ByVal value As Integer)
            privateWidth = value
        End Set
    End Property

    Public Function CompareTo(ByVal other As Box) As Integer _
                        Implements IComparable(Of Box).CompareTo
        ' Compares Height, Length, and Width.
        If Me.Height.CompareTo(other.Height) <> 0 Then
            Return Me.Height.CompareTo(other.Height)
        ElseIf Me.Length.CompareTo(other.Length) <> 0 Then
            Return Me.Length.CompareTo(other.Length)
        ElseIf Me.Width.CompareTo(other.Width) <> 0 Then
            Return Me.Width.CompareTo(other.Width)
        Else
            Return 0
        End If
    End Function

End Class

備註

衍生自這個類別,以提供介面的自訂執行,以搭配 IComparer<T> SortedList<TKey,TValue> 和泛型類別等集合類別使用 SortedDictionary<TKey,TValue>Derive from this class to provide a custom implementation of the IComparer<T> interface for use with collection classes such as the SortedList<TKey,TValue> and SortedDictionary<TKey,TValue> generic classes.

衍生自 Comparer<T> 類別和執行介面的差異如下 System.IComparableThe difference between deriving from the Comparer<T> class and implementing the System.IComparable interface is as follows:

  • 若要指定預設應該如何比較兩個物件,請 System.IComparable 在您的類別中執行介面。To specify how two objects should be compared by default, implement the System.IComparable interface in your class. 這可確保排序作業會使用您所提供的預設比較程式碼。This ensures that sort operations will use the default comparison code that you provided.

  • 若要定義要使用的比較子,而不使用預設的比較子,請從 Comparer<T> 類別衍生。To define a comparer to use instead of the default comparer, derive from the Comparer<T> class. 然後,您可以在採用比較子作為參數的排序作業中使用此比較子。You can then use this comparer in sort operations that take a comparer as a parameter.

屬性傳回的物件會 Default 使用 System.IComparable<T> c # 中的泛型介面 (IComparable<T>IComparable(Of T) Visual Basic) 來比較兩個物件。The object returned by the Default property uses the System.IComparable<T> generic interface (IComparable<T> in C#, IComparable(Of T) in Visual Basic) to compare two objects. 如果型別不 T 會實作為 System.IComparable<T> 泛型介面,則屬性會傳回 Default Comparer<T> 使用介面的 System.IComparableIf type T does not implement the System.IComparable<T> generic interface, the Default property returns a Comparer<T> that uses the System.IComparable interface.

給實施者的注意事項

Compare(T, T) 而且 System.Collections.Generic.EqualityComparer`1.Equals(`0,\`0) 在區分文化特性和區分大小寫方面可能會有不同的行為。 System.Collections.Generic.Comparer`1.Compare(`0,\`0) and System.Collections.Generic.EqualityComparer`1.Equals(`0,\`0) may behave differently in terms of culture-sensitivity and case-sensitivity.

針對字串比較, StringComparer 建議將類別用於比較子 < 字串 > For string comparisons, the StringComparer class is recommended over Comparer<String>. 類別的屬性 StringComparer 會傳回預先定義的實例,這些實例會使用不同的文化特性區分和區分大小寫組合來執行字串比較。Properties of the StringComparer class return predefined instances that perform string comparisons with different combinations of culture-sensitivity and case-sensitivity. 區分大小寫和區分文化特性在相同實例的成員之間是一致的 StringComparerThe case-sensitivity and culture-sensitivity are consistent among the members of the same StringComparer instance.

如需特定文化特性比較的詳細資訊,請參閱 System.Globalization 命名空間和 全球化和當地語系化For more information on culture-specific comparisons, see the System.Globalization namespace and Globalization and Localization.

建構函式

Comparer<T>()

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

屬性

Default

傳回泛型引數指定之型別的預設排序次序比較子 (Comparer)。Returns a default sort order comparer for the type specified by the generic argument.

方法

Compare(T, T)

在衍生類別中覆寫時,比較型別相同的兩個物件並傳回值,指出一個物件是小於、等於還是大於另一個物件。When overridden in a derived class, performs a comparison of two objects of the same type and returns a value indicating whether one object is less than, equal to, or greater than the other.

Create(Comparison<T>)

使用指定的比較建立比較子。Creates a comparer by using the specified comparison.

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.

(繼承來源 Object)
GetHashCode()

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

(繼承來源 Object)
GetType()

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

(繼承來源 Object)
MemberwiseClone()

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

(繼承來源 Object)
ToString()

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

(繼承來源 Object)

明確介面實作

IComparer.Compare(Object, Object)

比較兩個物件並傳回值,指出其中一個物件為小於、等於或大於另一個物件。Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.

適用於

另請參閱