Comparison<T> Comparison<T> Comparison<T> Comparison<T> Delegate

Определение

Представляет метод, сравнивающий два объекта одного типа.Represents the method that compares two objects of the same type.

generic <typename T>
public delegate int Comparison(T x, T y);
public delegate int Comparison<in T>(T x, T y);
type Comparison<'T> = delegate of 'T * 'T -> int
Public Delegate Function Comparison(Of In T)(x As T, y As T) As Integer 

Параметры типа

T

Тип сравниваемых объектов.The type of the objects to compare.

Параметры

x

Первый из сравниваемых объектов.The first object to compare.

y

Второй из сравниваемых объектов.The second object to compare.

Возвращаемое значение

System.Int32

Знаковое целое число, которое определяет относительные значения параметров x и y, как показано в следующей таблице.A signed integer that indicates the relative values of x and y, as shown in the following table.

ЗначениеValue ЗначениеMeaning
Меньше 0Less than 0 Значение x меньше y.x is less than y.
00 x равняется y.x equals y.
Больше 0Greater than 0 Значение x больше значения y.x is greater than y.
Наследование
Comparison<T>Comparison<T>Comparison<T>Comparison<T>

Примеры

В следующем примере кода демонстрируется использование Comparison<T> делегат со Sort(Comparison<T>) перегрузки метода.The following code example demonstrates the use of the Comparison<T> delegate with the Sort(Comparison<T>) method overload.

В примере кода определяется метод альтернативное сравнение строк с именем CompareDinosByLength.The code example defines an alternative comparison method for strings, named CompareDinosByLength. Этот метод работает следующим образом: Во-первых, сравниваемых null, и ссылкой на null, считается меньше, чем отличный от null.This method works as follows: First, the comparands are tested for null, and a null reference is treated as less than a non-null. Во-вторых длины строк сравниваются, и значение, считается более длинной строки.Second, the string lengths are compared, and the longer string is deemed to be greater. В-третьих Если значения длины равны, используется обычное сравнение строк.Third, if the lengths are equal, ordinary string comparison is used.

Объект List<T> строк создается и заполняется с четырьмя строками в произвольном порядке.A List<T> of strings is created and populated with four strings, in no particular order. Список также содержит пустую строку, а также ссылку на null.The list also includes an empty string and a null reference. Список, при сортировке Comparison<T> универсальный делегат, представляющий CompareDinosByLength метод и отображаться в дальнейшем.The list is displayed, sorted using a Comparison<T> generic delegate representing the CompareDinosByLength method, and displayed again.

using namespace System;
using namespace System::Collections::Generic;

int CompareDinosByLength(String^ x, String^ y)
{
    if (x == nullptr)
    {
        if (y == nullptr)
        {
            // If x is null and y is null, they're
            // equal. 
            return 0;
        }
        else
        {
            // If x is null and y is not null, y
            // is greater. 
            return -1;
        }
    }
    else
    {
        // If x is not null...
        //
        if (y == nullptr)
            // ...and y is null, x is greater.
        {
            return 1;
        }
        else
        {
            // ...and y is not null, compare the 
            // lengths of the two strings.
            //
            int retval = x->Length.CompareTo(y->Length);

            if (retval != 0)
            {
                // If the strings are not of equal length,
                // the longer string is greater.
                //
                return retval;
            }
            else
            {
                // If the strings are of equal length,
                // sort them with ordinary string comparison.
                //
                return x->CompareTo(y);
            }
        }
    }
};

void Display(List<String^>^ list)
{
    Console::WriteLine();
    for each(String^ s in list)
    {
        if (s == nullptr)
            Console::WriteLine("(null)");
        else
            Console::WriteLine("\"{0}\"", s);
    }
};

void main()
{
    List<String^>^ dinosaurs = gcnew List<String^>();
    dinosaurs->Add("Pachycephalosaurus");
    dinosaurs->Add("Amargasaurus");
    dinosaurs->Add("");
    dinosaurs->Add(nullptr);
    dinosaurs->Add("Mamenchisaurus");
    dinosaurs->Add("Deinonychus");
    Display(dinosaurs);

    Console::WriteLine("\nSort with generic Comparison<String^> delegate:");
    dinosaurs->Sort(
        gcnew Comparison<String^>(CompareDinosByLength));
    Display(dinosaurs);

}

/* This code example produces the following output:

"Pachycephalosaurus"
"Amargasaurus"
""
(null)
"Mamenchisaurus"
"Deinonychus"

Sort with generic Comparison<String^> delegate:

(null)
""
"Deinonychus"
"Amargasaurus"
"Mamenchisaurus"
"Pachycephalosaurus"
 */
using System;
using System.Collections.Generic;

public class Example
{
    private static int CompareDinosByLength(string x, string y)
    {
        if (x == null)
        {
            if (y == null)
            {
                // If x is null and y is null, they're
                // equal. 
                return 0;
            }
            else
            {
                // If x is null and y is not null, y
                // is greater. 
                return -1;
            }
        }
        else
        {
            // If x is not null...
            //
            if (y == null)
                // ...and y is null, x is greater.
            {
                return 1;
            }
            else
            {
                // ...and y is not null, compare the 
                // lengths of the two strings.
                //
                int retval = x.Length.CompareTo(y.Length);

                if (retval != 0)
                {
                    // If the strings are not of equal length,
                    // the longer string is greater.
                    //
                    return retval;
                }
                else
                {
                    // If the strings are of equal length,
                    // sort them with ordinary string comparison.
                    //
                    return x.CompareTo(y);
                }
            }
        }
    }

    public static void Main()
    {
        List<string> dinosaurs = new List<string>();
        dinosaurs.Add("Pachycephalosaurus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("");
        dinosaurs.Add(null);
        dinosaurs.Add("Mamenchisaurus");
        dinosaurs.Add("Deinonychus");
        Display(dinosaurs);

        Console.WriteLine("\nSort with generic Comparison<string> delegate:");
        dinosaurs.Sort(CompareDinosByLength);
        Display(dinosaurs);

    }

    private static void Display(List<string> list)
    {
        Console.WriteLine();
        foreach( string s in list )
        {
            if (s == null)
                Console.WriteLine("(null)");
            else
                Console.WriteLine("\"{0}\"", s);
        }
    }
}

/* This code example produces the following output:

"Pachycephalosaurus"
"Amargasaurus"
""
(null)
"Mamenchisaurus"
"Deinonychus"

Sort with generic Comparison<string> delegate:

(null)
""
"Deinonychus"
"Amargasaurus"
"Mamenchisaurus"
"Pachycephalosaurus"
 */
Imports System
Imports System.Collections.Generic

Public Class Example

    Private Shared Function CompareDinosByLength( _
        ByVal x As String, ByVal y As String) As Integer

        If x Is Nothing Then
            If y Is Nothing Then 
                ' If x is Nothing and y is Nothing, they're
                ' equal. 
                Return 0
            Else
                ' If x is Nothing and y is not Nothing, y
                ' is greater. 
                Return -1
            End If
        Else
            ' If x is not Nothing...
            '
            If y Is Nothing Then
                ' ...and y is Nothing, x is greater.
                Return 1
            Else
                ' ...and y is not Nothing, compare the 
                ' lengths of the two strings.
                '
                Dim retval As Integer = _
                    x.Length.CompareTo(y.Length)

                If retval <> 0 Then 
                    ' If the strings are not of equal length,
                    ' the longer string is greater.
                    '
                    Return retval
                Else
                    ' If the strings are of equal length,
                    ' sort them with ordinary string comparison.
                    '
                    Return x.CompareTo(y)
                End If
            End If
        End If

    End Function

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)
        dinosaurs.Add("Pachycephalosaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("")
        dinosaurs.Add(Nothing)
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Deinonychus")
        Display(dinosaurs)

        Console.WriteLine(vbLf & "Sort with generic Comparison(Of String) delegate:")
        dinosaurs.Sort(AddressOf CompareDinosByLength)
        Display(dinosaurs)

    End Sub

    Private Shared Sub Display(ByVal lis As List(Of String))
        Console.WriteLine()
        For Each s As String In lis
            If s Is Nothing Then
                Console.WriteLine("(Nothing)")
            Else
                Console.WriteLine("""{0}""", s)
            End If
        Next
    End Sub
End Class

' This code example produces the following output:
'
'"Pachycephalosaurus"
'"Amargasaurus"
'""
'(Nothing)
'"Mamenchisaurus"
'"Deinonychus"
'
'Sort with generic Comparison(Of String) delegate:
'
'(Nothing)
'""
'"Deinonychus"
'"Amargasaurus"
'"Mamenchisaurus"
'"Pachycephalosaurus"

В следующем примере используется Comparison<T> делегат для сортировки элементов в коллекцию CityInfo объектов.The following example uses the Comparison<T> delegate to sort the elements of a collection of CityInfo objects. CityInfo — Это класс, определяемый приложением, который содержит сведения о городе и населения.CityInfo is an application-defined class that contains information about a city and its population. В примере определяются три метода CompareByName, CompareByPopulation, и CompareByNames, обеспечивающие три различных способа упорядочения CityInfo объектов.The example defines three methods, CompareByName, CompareByPopulation, and CompareByNames, that offer three different ways of ordering the CityInfo objects. Каждый метод назначается comparison аргумент Array.Sort<T>(T[], Comparison<T>) метод.Each method is assigned to the comparison argument of the Array.Sort<T>(T[], Comparison<T>) method.

using System;

public class CityInfo
{
   string cityName;
   string countryName;
   int pop2010;
   
   public CityInfo(string name, string country, int pop2010)
   {
      this.cityName = name;
      this.countryName = country;
      this.pop2010 = pop2010;
   }
   
   public string City
   { get { return this.cityName; } } 
   
   public string Country
   { get { return this.countryName; } }

   public int Population
   { get { return this.pop2010; } }
   
   public static int CompareByName(CityInfo city1, CityInfo city2)
   { 
      return String.Compare(city1.City, city2.City);
   }
   
   public static int CompareByPopulation(CityInfo city1, CityInfo city2)
   {
      return city1.Population.CompareTo(city2.Population);
   }
   
   public static int CompareByNames(CityInfo city1, CityInfo city2)
   {
      return String.Compare(city1.Country + city1.City, city2.Country + city2.City);
   }      
}

public class Example
{
   public static void Main()
   {
      CityInfo NYC = new CityInfo("New York City", "United States of America", 8175133 );
      CityInfo Det = new CityInfo("Detroit", "United States of America", 713777);
      CityInfo Paris = new CityInfo("Paris", "France",  2193031);
      CityInfo[] cities = { NYC, Det, Paris };
      // Display ordered array.
      DisplayArray(cities);
      
      // Sort array by city name.
      Array.Sort(cities, CityInfo.CompareByName);
      DisplayArray(cities);
      
      // Sort array by population.
      Array.Sort(cities, CityInfo.CompareByPopulation);
      DisplayArray(cities);
      
      // Sort array by country + city name.
      Array.Sort(cities, CityInfo.CompareByNames);
      DisplayArray(cities);
   }
   
   private static void DisplayArray(CityInfo[] cities)
   {
      Console.WriteLine("{0,-20} {1,-25} {2,10}", "City", "Country", "Population");
      foreach (var city in cities)
         Console.WriteLine("{0,-20} {1,-25} {2,10:N0}", city.City, 
                           city.Country, city.Population);

      Console.WriteLine();
   }
}
// The example displays the following output:
//     City                 Country                   Population
//     New York City        United States of America   8,175,133
//     Detroit              United States of America     713,777
//     Paris                France                     2,193,031
//     
//     City                 Country                   Population
//     Detroit              United States of America     713,777
//     New York City        United States of America   8,175,133
//     Paris                France                     2,193,031
//     
//     City                 Country                   Population
//     Detroit              United States of America     713,777
//     Paris                France                     2,193,031
//     New York City        United States of America   8,175,133
//     
//     City                 Country                   Population
//     Paris                France                     2,193,031
//     Detroit              United States of America     713,777
//     New York City        United States of America   8,175,133
Public Class CityInfo
   Dim cityName As String
   Dim countryName As String
   Dim pop2010 As Integer
   
   Public Sub New(name As String, country As String, pop2010 As Integer)
      Me.cityName = name
      Me.countryName = country
      Me.pop2010 = pop2010
   End Sub
   
   Public ReadOnly Property City As String
      Get
         Return Me.cityName
      End Get
   End Property
   
   Public ReadOnly Property Country As String
      Get
         Return Me.countryName
      End Get
   End Property
   
   Public ReadOnly Property Population As Integer
      Get
         Return Me.pop2010
      End Get   
   End Property
   
   Public Shared Function CompareByName(city1 As CityInfo, city2 As CityInfo) As Integer
      Return String.Compare(city1.City, city2.City)
   End Function
   
   Public Shared Function CompareByPopulation(city1 As CityInfo, city2 As CityInfo) As Integer
      Return city1.Population.CompareTo(city2.Population)
   End Function
   
   Public Shared Function CompareByNames(city1 As CityInfo, city2 As CityInfo) As Integer
      Return String.Compare(city1.Country + city1.City, city2.Country + city2.City)
   End Function   
End Class

Module Example
   Public Sub Main()
      Dim NYC As New CityInfo("New York City", "United States of America", 8175133)
      Dim Det As New CityInfo("Detroit", "United States of America", 713777)
      Dim Paris As New CityInfo("Paris", "France", 2193031)
      Dim cities As CityInfo() = { NYC, Det, Paris }
      ' Display ordered array.
      DisplayArray(cities)
      
      ' Sort array by city name.
      Array.Sort(cities, AddressOf CityInfo.CompareByName)
      DisplayArray(cities)
      
      ' Sort array by population.
      Array.Sort(cities, AddressOf CityInfo.CompareByPopulation)
      DisplayArray(cities)
      
      ' Sort array by country + city name.
      Array.Sort(cities, AddressOf CityInfo.CompareByNames)
      DisplayArray(cities)
   End Sub
   
   Private Sub DisplayArray(cities() As CityInfo)
      Console.WriteLine("{0,-20} {1,-25} {2,10}", "City", "Country", "Population")
      For Each city In cities
         Console.WriteLine("{0,-20} {1,-25} {2,10:N0}", city.City, city.Country, city.Population)
      Next
      Console.WriteLine()
   End Sub
End Module
' The example displays the following output:
'     City                 Country                   Population
'     New York City        United States of America   8,175,133
'     Detroit              United States of America     713,777
'     Paris                France                     2,193,031
'     
'     City                 Country                   Population
'     Detroit              United States of America     713,777
'     New York City        United States of America   8,175,133
'     Paris                France                     2,193,031
'     
'     City                 Country                   Population
'     Detroit              United States of America     713,777
'     Paris                France                     2,193,031
'     New York City        United States of America   8,175,133
'     
'     City                 Country                   Population
'     Paris                France                     2,193,031
'     Detroit              United States of America     713,777
'     New York City        United States of America   8,175,133

Комментарии

Этот делегат используется Sort<T>(T[], Comparison<T>) перегрузка метода Array класс и Sort(Comparison<T>) перегрузка метода List<T> класса для сортировки элементов массива или списка.This delegate is used by the Sort<T>(T[], Comparison<T>) method overload of the Array class and the Sort(Comparison<T>) method overload of the List<T> class to sort the elements of an array or list.

Extension Methods

GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate)

Возвращает объект, представляющий метод, представленный указанным делегатом.Gets an object that represents the method represented by the specified delegate.

Применяется к

Дополнительно