Action<T1,T2,T3> Делегат

Определение

generic <typename T1, typename T2, typename T3>
public delegate void Action(T1 arg1, T2 arg2, T3 arg3);

public delegate void Action<in T1,in T2,in T3>(T1 arg1, T2 arg2, T3 arg3);

public delegate void Action<T1,T2,T3>(T1 arg1, T2 arg2, T3 arg3);

type Action<'T1, 'T2, 'T3> = delegate of 'T1 * 'T2 * 'T3 -> unit

Public Delegate Sub Action(Of In T1, In T2, In T3)(arg1 As T1, arg2 As T2, arg3 As T3)

Public Delegate Sub Action(Of T1, T2, T3)(arg1 As T1, arg2 As T2, arg3 As T3)

Параметры типа

Параметры

Наследование

Object

Delegate

Action<T1,T2,T3>

Комментарии

Делегат можно использовать Action<T1,T2,T3> для передачи метода в качестве параметра без явного объявления пользовательского делегата.You can use the Action<T1,T2,T3> delegate to pass a method as a parameter without explicitly declaring a custom delegate. Инкапсулированный метод должен соответствовать сигнатуре метода, определяемого этим делегатом.The encapsulated method must correspond to the method signature that is defined by this delegate. Это означает, что инкапсулированный метод должен иметь три параметра, которые передаются ему по значению и не должны возвращать значение.This means that the encapsulated method must have three parameters that are all passed to it by value, and it must not return a value. (В C# метод должен возвращать void .(In C#, the method must return void. В Visual Basic он должен быть определен с помощью Sub ...End SubIn Visual Basic, it must be defined by the Sub…End Sub создания.construct. Это также может быть метод, возвращающий значение, которое игнорируется.) Как правило, такой метод используется для выполнения операции.It can also be a method that returns a value that is ignored.) Typically, such a method is used to perform an operation.

При использовании Action<T1,T2,T3> делегата нет необходимости явно определять делегат, инкапсулирующий метод с тремя параметрами.When you use the Action<T1,T2,T3> delegate, you do not have to explicitly define a delegate that encapsulates a method with three parameters. Например, следующий код явно объявляет делегат с именем StringCopy и присваивает ссылку на CopyStrings метод его экземпляру делегата.For example, the following code explicitly declares a delegate named StringCopy and assigns a reference to the CopyStrings method to its delegate instance.

using System;

delegate void StringCopy(string[] stringArray1,
                         string[] stringArray2,
                         int indexToStart);

public class TestDelegate
{
   public static void Main()
   {
      string[] ordinals = {"First", "Second", "Third", "Fourth", "Fifth"};
      string[] copiedOrdinals = new string[ordinals.Length];
      StringCopy copyOperation = CopyStrings;
      copyOperation(ordinals, copiedOrdinals, 3);
      foreach (string ordinal in copiedOrdinals)
         Console.WriteLine(String.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
   }

   private static void CopyStrings(string[] source, string[] target, int startPos)
   {
      if (source.Length != target.Length)
         throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

      for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
         target[ctr] = String.Copy(source[ctr]);
   }
}

Delegate Sub StringCopy(stringArray1() As String, _
                        stringArray2() As String, _
                        indexToStart As Integer)

Module TestDelegate
   Public Sub Main()
      Dim ordinals() As String = {"First", "Second", "Third", "Fourth", "Fifth"}
      Dim copiedOrdinals(ordinals.Length - 1) As String
      Dim copyOperation As StringCopy = AddressOf CopyStrings
      copyOperation(ordinals, copiedOrdinals, 3)
      For Each ordinal As String In copiedOrdinals
         Console.WriteLine(ordinal)
      Next    
   End Sub
   
   Private Sub CopyStrings(source() As String, target() As String, startPos As Integer)
      If source.Length <> target.Length Then 
         Throw New IndexOutOfRangeException("The source and target arrays must have the same number of elements.")
      End If
      For ctr As Integer = startPos to source.Length - 1
         target(ctr) = String.Copy(source(ctr))
      Next
   End Sub
End Module

В следующем примере этот код упрощается путем создания экземпляра Action<T1,T2,T3> делегата вместо явного определения нового делегата и назначения ему именованного метода.The following example simplifies this code by instantiating the Action<T1,T2,T3> delegate instead of explicitly defining a new delegate and assigning a named method to it.

using System;

public class TestAction3
{
   public static void Main()
   {
      string[] ordinals = {"First", "Second", "Third", "Fourth", "Fifth"};
      string[] copiedOrdinals = new string[ordinals.Length];
      Action<string[], string[], int> copyOperation = CopyStrings;
      copyOperation(ordinals, copiedOrdinals, 3);
      foreach (string ordinal in copiedOrdinals)
         Console.WriteLine(String.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
   }

   private static void CopyStrings(string[] source, string[] target, int startPos)
   {
      if (source.Length != target.Length)
         throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

      for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
         target[ctr] = String.Copy(source[ctr]);
   }
}

Module TestAction3
   Public Sub Main()
      Dim ordinals() As String = {"First", "Second", "Third", "Fourth", "Fifth"}
      Dim copiedOrdinals(ordinals.Length - 1) As String
      Dim copyOperation As Action(Of String(), String(), Integer) = AddressOf CopyStrings
      copyOperation(ordinals, copiedOrdinals, 3)
      For Each ordinal As String In copiedOrdinals
         Console.WriteLine(ordinal)
      Next    
   End Sub
   
   Private Sub CopyStrings(source() As String, target() As String, startPos As Integer)
      If source.Length <> target.Length Then 
         Throw New IndexOutOfRangeException("The source and target arrays must have the same number of elements.")
      End If
      For ctr As Integer = startPos to source.Length - 1
         target(ctr) = String.Copy(source(ctr))
      Next
   End Sub
End Module

Также можно использовать Action<T1,T2,T3> делегат с анонимными методами в C#, как показано в следующем примере.You can also use the Action<T1,T2,T3> delegate with anonymous methods in C#, as the following example illustrates. (Общие сведения о анонимных методах см. в разделе анонимные методы.)(For an introduction to anonymous methods, see Anonymous Methods.)

using System;

public class TestAnon
{
   public static void Main()
   {
      string[] ordinals = {"First", "Second", "Third", "Fourth", "Fifth"};
      string[] copiedOrdinals = new string[ordinals.Length];
      Action<string[], string[], int> copyOperation = delegate(string[] s1,
                                                               string[] s2,
                                                               int pos)
                                      { CopyStrings(s1, s2, pos); };
      copyOperation(ordinals, copiedOrdinals, 3);
      foreach (string ordinal in copiedOrdinals)
         Console.WriteLine(String.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
   }

   private static void CopyStrings(string[] source, string[] target, int startPos)
   {
      if (source.Length != target.Length)
         throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

      for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
         target[ctr] = String.Copy(source[ctr]);
   }
}

Можно также назначить лямбда-выражение Action<T1,T2,T3> экземпляру делегата, как показано в следующем примере.You can also assign a lambda expression to an Action<T1,T2,T3> delegate instance, as the following example illustrates. (Общие сведения о лямбда-выражениях см. в разделе лямбда-выражения.)(For an introduction to lambda expressions, see Lambda Expressions.)

using System;

public class TestLambda
{
   public static void Main()
   {
      string[] ordinals = {"First", "Second", "Third", "Fourth", "Fifth"};
      string[] copiedOrdinals = new string[ordinals.Length];
      Action<string[], string[], int> copyOperation = (s1, s2, pos) =>
                                      CopyStrings(s1, s2, pos);
      copyOperation(ordinals, copiedOrdinals, 3);
      foreach (string ordinal in copiedOrdinals)
         Console.WriteLine(ordinal == string.Empty ? "<None>" : ordinal);
   }

   private static void CopyStrings(string[] source, string[] target, int startPos)
   {
      if (source.Length != target.Length)
         throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

      for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
         target[ctr] = String.Copy(source[ctr]);
   }
}

Public Module TestLambda
   Public Sub Main()
      Dim ordinals() As String = {"First", "Second", "Third", "Fourth", "Fifth"}
      Dim copiedOrdinals(ordinals.Length - 1) As String           
      Dim copyOperation As Action(Of String(), String(), Integer) = _
                           Sub(s1, s2, pos) CopyStrings(s1, s2, pos) 
      copyOperation(ordinals, copiedOrdinals, 3)
      For Each ordinal As String In copiedOrdinals
         If String.IsNullOrEmpty(ordinal) Then
            Console.WriteLine("<None>")
         Else
            Console.WriteLine(ordinal)
         End If      
      Next   
   End Sub

   Private Function CopyStrings(source() As String, target() As String, startPos As Integer) As Integer
      If source.Length <> target.Length Then 
         Throw New IndexOutOfRangeException("The source and target arrays must have the same number of elements.")
      End If
      
      For ctr As Integer = startPos To source.Length - 1 
         target(ctr) = String.Copy(source(ctr))
      Next
      Return source.Length - startPos 
   End Function
End Module
' The example displays the following output:
'       Fourth
'       Fifth

Методы расширения

Применяется к

См. также раздел

• Func<T1,T2,T3,TResult>