Comparer<T> Classe

Definição

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)

Parâmetros de tipo

Herança

Object

Comparer<T>

Atributos

SerializableAttribute

Implementações

IComparer<T> IComparer

Exemplos

O exemplo a seguir deriva uma classe , BoxLengthFirst, da Comparer<T> classe . Esse comparador compara dois objetos do tipo Box. Ele os classifica primeiro por comprimento, depois por altura e, em seguida, por largura. A Box classe implementa a IComparable<T> interface para controlar a comparação padrão entre dois Box objetos. Essa implementação padrão classifica primeiro por altura, depois por comprimento e, em seguida, por largura. O exemplo mostra as diferenças entre as duas comparações classificando uma lista de Box objetos primeiro usando o BoxLengthFirst comparador e, em seguida, usando o comparador padrão.

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

Comentários

Deriva dessa classe para fornecer uma implementação personalizada da IComparer<T> interface para uso com classes de coleção, como as SortedList<TKey,TValue> classes genéricas e SortedDictionary<TKey,TValue> .

A diferença entre derivar da Comparer<T> classe e implementar a interface é a System.IComparable seguinte:

• Para especificar como dois objetos devem ser comparados por padrão, implemente a System.IComparable interface em sua classe. Isso garante que as operações de classificação usem o código de comparação padrão que você forneceu.

• Para definir um comparador a ser usado em vez do comparador padrão, derive da Comparer<T> classe . Em seguida, você pode usar esse comparador em operações de classificação que usam um comparador como um parâmetro.

O objeto retornado pela Default propriedade usa a System.IComparable<T> interface genérica (IComparable<T> em C#, IComparable(Of T) no Visual Basic) para comparar dois objetos. Se o tipo T não implementar a System.IComparable<T> interface genérica, a Default propriedade retornará um Comparer<T> que usa a System.IComparable interface .

Notas aos Implementadores

Compare(T, T) e Equals(T, T) podem se comportar de forma diferente em termos de confidencialidade de cultura e diferenciação de maiúsculas e minúsculas.

Para comparações de cadeia de caracteres, a StringComparer classe é recomendada em .Comparer<String> As propriedades da StringComparer classe retornam instâncias predefinidas que executam comparações de cadeia de caracteres com diferentes combinações de confidencialidade de cultura e diferenciação de maiúsculas e minúsculas. A diferenciação de maiúsculas e minúsculas e a sensibilidade à cultura são consistentes entre os membros da mesma StringComparer instância.

Para obter mais informações sobre comparações específicas da cultura, consulte o System.Globalization namespace e Globalização e Localização.

Construtores

Propriedades

Métodos

Implantações explícitas de interface

Aplica-se a

Confira também

• IComparer<T>
• IComparable<T>
• StringComparer
• CultureInfo