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

定義

同じ型の 2 つのオブジェクトを比較するメソッドを表します。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 

型パラメーター

T

比較するオブジェクトの型。The type of the objects to compare.

パラメーター

x

比較する最初のオブジェクト。The first object to compare.

y

比較する 2 番目のオブジェクト。The second object to compare.

戻り値

System.Int32

xy の相対値を示す符号付き整数。次の表を参照してください。A signed integer that indicates the relative values of x and y, as shown in the following table.

[値]Value 説明Meaning
0 より小さい。Less than 0 xy より小さい値です。x is less than y.
00 xy は等しい。x equals y.
0 より大きい。Greater than 0 xy より大きくなっています。x is greater than y.
継承
Comparison<T>Comparison<T>Comparison<T>Comparison<T>

次のコード例は、の使用を示します、Comparison<T>を持つデリゲート、Sort(Comparison<T>)メソッドのオーバー ロードします。The following code example demonstrates the use of the Comparison<T> delegate with the Sort(Comparison<T>) method overload.

コード例は、という名前の文字列の代替の比較メソッドを定義CompareDinosByLengthします。The code example defines an alternative comparison method for strings, named CompareDinosByLength. このメソッドは、次のように機能します。最初にの比較対照値がテストされますnull、null 参照が null でない未満として扱われます。This method works as follows: First, the comparands are tested for null, and a null reference is treated as less than a non-null. 次に、文字列の長さを比較してより長い文字列が大きいと見なされます。Second, the string lengths are compared, and the longer string is deemed to be greater. 3 番目に、長さが等しい場合は、通常の文字列比較が使用されます。Third, if the lengths are equal, ordinary string comparison is used.

AList<T>文字列の任意の順序で、4 つの文字列を設定して作成されます。A List<T> of strings is created and populated with four strings, in no particular order. 一覧には、空の文字列と null 参照も含まれています。The list also includes an empty string and a null reference. 一覧を表示すると、並べ替えを使用して、Comparison<T>を表すジェネリック デリゲート、CompareDinosByLengthメソッドを再び表示されます。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"

次の例では、Comparison<T>デリゲートのコレクションの要素を並べ替えるCityInfoオブジェクト。The following example uses the Comparison<T> delegate to sort the elements of a collection of CityInfo objects. CityInfo 都市とその人口に関する情報を含むアプリケーションで定義されたクラスです。CityInfo is an application-defined class that contains information about a city and its population. 例では、3 つのメソッドを定義します。 CompareByNameCompareByPopulation、およびCompareByNames、順序付けの 3 つの方法を提供する、CityInfoオブジェクト。The example defines three methods, CompareByName, CompareByPopulation, and CompareByNames, that offer three different ways of ordering the CityInfo objects. 割り当てられているそれぞれの方法、comparisonの引数、Array.Sort<T>(T[], Comparison<T>)メソッド。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

注釈

このデリゲートを使用して、Sort<T>(T[], Comparison<T>)のメソッドのオーバー ロード、ArrayクラスとSort(Comparison<T>)のメソッドのオーバー ロード、List<T>クラス、配列またはリストの要素を並べ替えるに。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.

拡張メソッド

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

指定したデリゲートによって表されるメソッドを表すオブジェクトを取得します。Gets an object that represents the method represented by the specified delegate.

適用対象

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