Comparer<T> Classe

Definição

Fornece uma classe base para implementações da interface genérica IComparer<T>.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
[System.Serializable]
public abstract class Comparer<T> : System.Collections.Generic.IComparer<T>, System.Collections.IComparer
type Comparer<'T> = class
    interface IComparer
    interface IComparer<'T>
Public MustInherit Class Comparer(Of T)
Implements IComparer, IComparer(Of T)

Parâmetros de tipo

T

O tipo de objetos a serem comparados.The type of objects to compare.

Herança
Comparer<T>
Atributos
Implementações

Exemplos

O exemplo a seguir deriva uma classe, BoxLengthFirst, da classe Comparer<T>.The following example derives a class, BoxLengthFirst, from the Comparer<T> class. Este comparador compara dois objetos do tipo Box.This comparer compares two objects of type Box. Ele os classifica primeiro por comprimento, depois por altura e, em seguida, por largura.It sorts them first by length, then by height, and then by width. A classe Box implementa a interface IComparable<T> para controlar a comparação padrão entre dois objetos Box.The Box class implements the IComparable<T> interface to control the default comparison between two Box objects. Essa implementação padrão é classificada primeiro por altura, depois por comprimento e, em seguida, por largura.This default implementation sorts first by height, then by length, and then by width. O exemplo mostra as diferenças entre as duas comparações classificando uma lista de objetos Box primeiro usando o comparador de BoxLengthFirst e, em seguida, usando o comparador padrão.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

Comentários

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

A diferença entre a derivação da classe Comparer<T> e a implementação da interface System.IComparable é a seguinte:The difference between deriving from the Comparer<T> class and implementing the System.IComparable interface is as follows:

  • Para especificar como dois objetos devem ser comparados por padrão, implemente a interface System.IComparable em sua classe.To specify how two objects should be compared by default, implement the System.IComparable interface in your class. Isso garante que as operações de classificação usarão o código de comparação padrão que você forneceu.This ensures that sort operations will use the default comparison code that you provided.

  • Para definir um comparador a ser usado em vez do comparador padrão, derive da classe Comparer<T>.To define a comparer to use instead of the default comparer, derive from the Comparer<T> class. Você pode usar esse comparador em operações de classificação que usam um comparador como parâmetro.You can then use this comparer in sort operations that take a comparer as a parameter.

O objeto retornado pela propriedade Default usa a interface genérica System.IComparable<T> (IComparable<T> em C#, IComparable(Of T) no Visual Basic) para comparar dois objetos.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. Se o tipo T não implementar a interface genérica System.IComparable<T>, a propriedade Default retornará um Comparer<T> que usa a interface System.IComparable.If type T does not implement the System.IComparable<T> generic interface, the Default property returns a Comparer<T> that uses the System.IComparable interface.

Notas aos Implementadores

Compare(T, T) e System.Collections.Generic.EqualityComparer`1.Equals(`0,\`0) podem se comportar de forma diferente em termos de sensibilidade à cultura e diferenciação de maiúsculas e minúsculas. 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. Para comparações de cadeias de caracteres, a classe StringComparer é recomendada sobre o comparador <cadeia de caracteres>.For string comparisons, the StringComparer class is recommended over Comparer<String>. As propriedades da classe StringComparer retornam instâncias predefinidas que executam comparações de cadeia de caracteres com diferentes combinações de sensibilidade à cultura e distinção entre maiúsculas e minúsculas.Properties of the StringComparer class return predefined instances that perform string comparisons with different combinations of culture-sensitivity and case-sensitivity. A diferenciação de maiúsculas e minúsculas e a sensibilidade de cultura são consistentes entre os membros da mesma instância de StringComparer.The case-sensitivity and culture-sensitivity are consistent among the members of the same StringComparer instance. Para obter mais informações sobre comparações específicas de cultura, consulte o namespace System.Globalization e a [globalização e localização](~/docs/standard/globalization-localization/index.md).For more information on culture-specific comparisons, see the System.Globalization namespace and [Globalization and Localization](~/docs/standard/globalization-localization/index.md).

Construtores

Comparer<T>()

Inicializa uma nova instância da classe Comparer<T>.Initializes a new instance of the Comparer<T> class.

Propriedades

Default

Retorna um comparador de ordem de classificação padrão para o tipo especificado pelo argumento genérico.Returns a default sort order comparer for the type specified by the generic argument.

Métodos

Compare(T, T)

Quando substituído em uma classe derivada, executa uma comparação de dois objetos do mesmo tipo e retorna um valor que indica se um objeto é menor que, igual a ou maior que o outro.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>)

Cria um comparador usando a comparação especificada.Creates a comparer by using the specified comparison.

Equals(Object)

Determina se o objeto especificado é igual ao objeto atual.Determines whether the specified object is equal to the current object.

(Herdado de Object)
GetHashCode()

Serve como a função de hash padrão.Serves as the default hash function.

(Herdado de Object)
GetType()

Obtém o Type da instância atual.Gets the Type of the current instance.

(Herdado de Object)
MemberwiseClone()

Cria uma cópia superficial do Object atual.Creates a shallow copy of the current Object.

(Herdado de Object)
ToString()

Retorna uma cadeia de caracteres que representa o objeto atual.Returns a string that represents the current object.

(Herdado de Object)

Implantações explícitas de interface

IComparer.Compare(Object, Object)

Compara dois objetos e retorna um valor que indica se um é menor, igual ou maior do que o outro.Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.

Aplica-se a

Veja também