Comparer<T> Classe

Definição

Espaço de Nomes:

System.Collections.Generic

Assemblagem:

mscorlib.dll

Fornece uma classe base para implementações da IComparer<T> interface genérica.

generic <typename T>
public ref class Comparer abstract : System::Collections::Generic::IComparer<T>, System::Collections::IComparer

[System.Serializable]
public abstract class Comparer<T> : System.Collections.Generic.IComparer<T>, System.Collections.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 Genérico

T

O tipo de objetos a comparar.

Herança

Object

Comparer<T>

Atributos

SerializableAttribute

Implementações

IComparer<T> IComparer

Exemplos

O exemplo seguinte deriva uma classe, BoxLengthFirst, a partir da Comparer<T> classe. Este comparador compara dois objetos do tipo Box. Ordena-os primeiro por comprimento, depois por altura e depois por largura. A Box classe implementa a IComparable<T> interface para controlar a comparação padrão entre dois Box objetos. Esta implementação padrão ordena primeiro por altura, depois por comprimento e finalmente por largura. O exemplo mostra as diferenças entre as duas comparações ordenando uma lista de Box objetos primeiro usando o BoxLengthFirst comparador e depois 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;
        }
    }
}

open System
open System.Collections.Generic

type Box(h, l, w) =
    member val Height: int = h with get
    member val Length: int = l with get
    member val Width: int = w with get

    interface IComparable<Box> with
        member this.CompareTo(other) =
            // Compares Height, Length, and Width.
            if this.Height.CompareTo other.Height <> 0 then
                this.Height.CompareTo other.Height
            elif this.Length.CompareTo other.Length <> 0 then
                this.Length.CompareTo other.Length
            elif this.Width.CompareTo other.Width <> 0 then
                this.Width.CompareTo other.Width
            else
                0

type BoxLengthFirst() =
    inherit Comparer<Box>()

    // Compares by Length, Height, and Width.
    override _.Compare(x: Box, y: Box) =
        if x.Length.CompareTo y.Length <> 0 then
            x.Length.CompareTo y.Length
        elif x.Height.CompareTo y.Height <> 0 then
            x.Height.CompareTo y.Height
        elif x.Width.CompareTo y.Width <> 0 then
            x.Width.CompareTo y.Width
        else
            0

let boxes = ResizeArray<Box>()
boxes.Add(Box(4, 20, 14))
boxes.Add(Box(12, 12, 12))
boxes.Add(Box(8, 20, 10))
boxes.Add(Box(6, 10, 2))
boxes.Add(Box(2, 8, 4))
boxes.Add(Box(2, 6, 8))
boxes.Add(Box(4, 12, 20))
boxes.Add(Box(18, 10, 4))
boxes.Add(Box(24, 4, 18))
boxes.Add(Box(10, 4, 16))
boxes.Add(Box(10, 2, 10))
boxes.Add(Box(6, 18, 2))
boxes.Add(Box(8, 12, 4))
boxes.Add(Box(12, 10, 8))
boxes.Add(Box(14, 6, 6))
boxes.Add(Box(16, 6, 16))
boxes.Add(Box(2, 8, 12))
boxes.Add(Box(4, 24, 8))
boxes.Add(Box(8, 6, 20))
boxes.Add(Box(18, 18, 12))

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

printfn "H - L - W"
printfn "=========="

for bx in boxes do
    printfn $"{bx.Height}\t{bx.Length}\t{bx.Width}"

printfn ""
printfn "H - L - W"
printfn "=========="

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

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

for bx in boxes do
    printfn $"{bx.Height}\t{bx.Length}\t{bx.Width}"


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

let bc = LengthFirst :> Comparer<Box>

let BoxA = Box(2, 6, 8)
let BoxB = Box(10, 12, 14)
let x = LengthFirst.Compare(BoxA, BoxB)
printfn $"\n{x}"

// 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>.
type BoxComp() =
    interface IComparer<Box> with
        // Compares by Height, Length, and Width.
        member _.Compare(x: Box, y: Box) =
            if x.Height.CompareTo(y.Height) <> 0 then
                x.Height.CompareTo(y.Height)
            elif x.Length.CompareTo(y.Length) <> 0 then
                x.Length.CompareTo(y.Length)
            elif x.Width.CompareTo(y.Width) <> 0 then
                x.Width.CompareTo(y.Width)
            else
                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

Observações

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

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

• Para especificar como dois objetos devem ser comparados por defeito, implemente a System.IComparable interface na sua classe. Isto garante que as operações de ordenação usarão o código de comparação padrão que forneceu.

• Para definir um comparador a usar em vez do comparador padrão, derive-se da Comparer<T> classe. Pode então usar este comparador em operações de ordenação que tomam um comparador como parâmetro.

O objeto devolvido pela propriedade Default usa a interface genérica System.IComparable<T> (IComparable<T> em C#, IComparable(Of T) em Visual Basic) para comparar dois objetos. Se type T não implementar a System.IComparable<T> interface genérica, a Default propriedade devolve a Comparer<T> que utiliza a System.IComparable interface.

Notas para Implementadores

Compare(T, T) e Equals(T, T) podem comportar-se de forma diferente em termos de sensibilidade à cultura e à sensibilidade a maiúsculas minúsculas.

Para comparações de cordas, recomenda-se a StringComparer classe em vez de Comparer<String>. As propriedades da StringComparer classe retornam instâncias pré-definidas que realizam comparações de cadeias com diferentes combinações de sensibilidade à cultura e sensibilidade a maiúsculas minúsculas. A sensibilidade ao caso e à cultura são consistentes entre os membros da mesma StringComparer instância.

Para mais informações sobre comparações específicas de culturas, consulte o System.Globalization namespace e Globalização e Localização.

Construtores

Name	Description
Comparer<T>()	Inicializa uma nova instância da Comparer<T> classe.

Propriedades

Name	Description
Default	Devolve um comparador de ordem de ordenação por defeito para o tipo especificado pelo argumento genérico.

Métodos

Name	Description
Compare(T, T)	Quando sobrescrito numa classe derivada, realiza uma comparação de dois objetos do mesmo tipo e devolve um valor que indica se um objeto é menor, igual ou maior que o outro.
Create(Comparison<T>)	Cria um comparador usando a comparação especificada.
Equals(Object)	Determina se o objeto especificado é igual ao objeto atual. (Herdado de Object)
GetHashCode()	Serve como função de hash predefinida. (Herdado de Object)
GetType()	Obtém o Type da instância atual. (Herdado de Object)
MemberwiseClone()	Cria uma cópia superficial do atual Object. (Herdado de Object)
ToString()	Devolve uma cadeia que representa o objeto atual. (Herdado de Object)

Implementações de Interface Explícita

Name	Description
IComparer.Compare(Object, Object)	Compara dois objetos e devolve um valor que indica se um é menor, igual ou maior que o outro.

Ver também

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