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

Definition

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 

Typparameter

Parameter

Rückgabewert

System.Int32

Eine ganze Zahl mit Vorzeichen, die die relativen Werte von x und y angibt, wie in der folgenden Tabelle veranschaulicht.A signed integer that indicates the relative values of x and y, as shown in the following table.

Vererbung

ObjectObjectObjectObject

DelegateDelegateDelegateDelegate

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

Beispiele

Das folgende Codebeispiel veranschaulicht die Verwendung von der Comparison<T> mit Delegieren der Sort(Comparison<T>) -methodenüberladung.The following code example demonstrates the use of the Comparison<T> delegate with the Sort(Comparison<T>) method overload.

Das Codebeispiel definiert eine alternative Vergleichsmethode für Zeichenfolgen wird mit dem Namen CompareDinosByLength.The code example defines an alternative comparison method for strings, named CompareDinosByLength. Diese Methode funktioniert wie folgt aus: Zunächst werden die zu vergleichenden Objekte für getestet null, und als kleiner als ein Wert ungleich Null ein null-Verweis behandelt wird.This method works as follows: First, the comparands are tested for null, and a null reference is treated as less than a non-null. Zweitens: die Länge der Zeichenfolge verglichen werden und größer sein als die längere Zeichenfolge angesehen wird.Second, the string lengths are compared, and the longer string is deemed to be greater. Wenn die Länge gleich sind, wird im dritten gewöhnliche Zeichenfolgenvergleich verwendet.Third, if the lengths are equal, ordinary string comparison is used.

Ein List<T> von Zeichenfolgen erstellt und mit vier Zeichenfolgen, in keiner bestimmten Reihenfolge aufgefüllt.A List<T> of strings is created and populated with four strings, in no particular order. Die Liste enthält auch eine leere Zeichenfolge und ein null-Verweis.The list also includes an empty string and a null reference. Die Liste wird angezeigt, sortiert, mit einem Comparison<T> generischen Delegaten darstellt der CompareDinosByLength -Methode, und erneut angezeigt.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"

Im folgenden Beispiel wird die Comparison<T> Delegat zum Sortieren der Elemente einer Auflistung von CityInfo Objekte.The following example uses the Comparison<T> delegate to sort the elements of a collection of CityInfo objects. CityInfo ist eine Anwendung definierte Klasse, die Informationen über eine Stadt und seiner Einwohnerzahl enthält.CityInfo is an application-defined class that contains information about a city and its population. Das Beispiel definiert drei Methoden, CompareByName, CompareByPopulation, und CompareByNames, bieten drei verschiedene Möglichkeiten zum Sortieren der CityInfo Objekte.The example defines three methods, CompareByName, CompareByPopulation, and CompareByNames, that offer three different ways of ordering the CityInfo objects. Jede Methode zugewiesen ist die comparison Argument der Array.Sort<T>(T[], Comparison<T>) Methode.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/Region", "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/Region            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/Region            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/Region            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/Region            Population
'     Paris                France                     2,193,031
'     Detroit              United States of America     713,777
'     New York City        United States of America   8,175,133

Hinweise

Dieser Delegat wird verwendet, indem die Sort<T>(T[], Comparison<T>) methodenüberladung der Array Klasse und die Sort(Comparison<T>) methodenüberladung der der List<T> Klasse sortiert die Elemente des Arrays oder einer Liste.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

Gilt für:

Siehe auch

• Sort<T>(T[], Comparison<T>)
• Sort(Comparison<T>)