Action<T1,T2> Delegat

Definicja

Hermetyzuje metodę, która ma dwa parametry i nie zwraca wartości.Encapsulates a method that has two parameters and does not return a value.

generic <typename T1, typename T2>
public delegate void Action(T1 arg1, T2 arg2);
public delegate void Action<in T1,in T2>(T1 arg1, T2 arg2);
type Action<'T1, 'T2> = delegate of 'T1 * 'T2 -> unit
Public Delegate Sub Action(Of In T1, In T2)(arg1 As T1, arg2 As T2)

Parametry typu

T1

Typ pierwszego parametru metody, który jest hermetyzowany przez ten delegat.The type of the first parameter of the method that this delegate encapsulates.

T2

Typ drugiego parametru metody, który jest hermetyzowany przez ten delegat.The type of the second parameter of the method that this delegate encapsulates.

Parametry

arg1

Pierwszy parametr metody, która jest hermetyzowana przez ten delegat.The first parameter of the method that this delegate encapsulates.

arg2

Drugi parametr metody, która jest hermetyzowana przez ten delegat.The second parameter of the method that this delegate encapsulates.

Dziedziczenie
Action<T1,T2>

Uwagi

Można użyć delegata Action<T1,T2>, aby przekazać metodę jako parametr bez jawnego deklarowania niestandardowego delegata.You can use the Action<T1,T2> delegate to pass a method as a parameter without explicitly declaring a custom delegate. Metoda hermetyzowana musi odpowiadać sygnaturze metody zdefiniowanej przez tego delegata.The encapsulated method must correspond to the method signature that is defined by this delegate. Oznacza to, że metoda hermetyzowana musi mieć dwa parametry, które są przesyłane do niego przez wartość, i nie może zwracać wartości.This means that the encapsulated method must have two parameters that are both passed to it by value, and it must not return a value. (W C#, metoda musi zwracać void.(In C#, the method must return void. W Visual Basic musi on być zdefiniowany przez Sub...End SubIn Visual Basic, it must be defined by the SubEnd Sub Konstruuj.construct. Może być również metodą zwracającą wartość, która jest ignorowana.) Zazwyczaj taka metoda jest używana do wykonywania operacji.It can also be a method that returns a value that is ignored.) Typically, such a method is used to perform an operation.

Uwaga

Aby odwołać się do metody, która ma dwa parametry i zwraca wartość, należy zamiast tego użyć delegata generycznego Func<T1,T2,TResult>.To reference a method that has two parameters and returns a value, use the generic Func<T1,T2,TResult> delegate instead.

W przypadku korzystania z delegata Action<T1,T2> nie trzeba jawnie definiować delegata, który hermetyzuje metodę z dwoma parametrami.When you use the Action<T1,T2> delegate, you do not have to explicitly define a delegate that encapsulates a method with two parameters. Na przykład poniższy kod jawnie deklaruje delegata o nazwie ConcatStrings.For example, the following code explicitly declares a delegate named ConcatStrings. Następnie przypisuje odwołanie do jednej z dwóch metod do jego wystąpienia delegata.It then assigns a reference to either of two methods to its delegate instance. Jedna metoda zapisuje dwa ciągi do konsoli; Druga zapisuje dwa ciągi do pliku.One method writes two strings to the console; the second writes two strings to a file.

using System;
using System.IO;

delegate void ConcatStrings(string string1, string string2);

public class TestDelegate
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      ConcatStrings concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = WriteToFile;
      else
         concat = WriteToConsole;
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}
Imports System.IO

Delegate Sub ConcatStrings(string1 As String, string2 As String)

Module TestDelegate
   Public Sub Main()
      
      Dim message1 As String = "The first line of a message."
      Dim message2 As String = "The second line of a message."
      Dim concat As ConcatStrings
      
      If Environment.GetCommandLineArgs().Length > 1 Then
         concat = AddressOf WriteToFile
      Else
         concat = AddressOf WriteToConsole
      End If   
      concat(message1, message2)         
   End Sub
   
   Private Sub WriteToConsole(string1 As String, string2 As String)
      Console.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
   End Sub
   
   Private Sub WriteToFile(string1 As String, string2 As String)
      Dim writer As StreamWriter = Nothing  
      Try
         writer = New StreamWriter(Environment.GetCommandLineArgs(1), False)
         writer.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
      Catch
         Console.WriteLine("File write operation failed...")
      Finally
         If writer IsNot Nothing Then writer.Close
      End Try      
   End Sub
End Module

Poniższy przykład upraszcza ten kod, tworząc wystąpienie delegata Action<T1,T2>, zamiast jawnie definiując nowy delegat i przypisując nazwaną metodę.The following example simplifies this code by instantiating the Action<T1,T2> delegate instead of explicitly defining a new delegate and assigning a named method to it.

using System;
using System.IO;

public class TestAction2
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      Action<string, string> concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = WriteToFile;
      else
         concat = WriteToConsole;
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}
Imports System.IO

Module TestAction2
   Public Sub Main()
      
      Dim message1 As String = "The first line of a message."
      Dim message2 As String = "The second line of a message."
      Dim concat As Action(Of String, String)
      
      If Environment.GetCommandLineArgs().Length > 1 Then
         concat = AddressOf WriteToFile
      Else
         concat = AddressOf WriteToConsole
      End If   
      concat(message1, message2)         
   End Sub
   
   Private Sub WriteToConsole(string1 As String, string2 As String)
      Console.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
   End Sub
   
   Private Sub WriteToFile(string1 As String, string2 As String)
      Dim writer As StreamWriter = Nothing  
      Try
         writer = New StreamWriter(Environment.GetCommandLineArgs(1), False)
         writer.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
      Catch
         Console.WriteLine("File write operation failed...")
      Finally
         If writer IsNot Nothing Then writer.Close
      End Try      
   End Sub
End Module

Można również użyć delegata Action<T1,T2> z metodami anonimowymi C#w, jak pokazano w poniższym przykładzie.You can also use the Action<T1,T2> delegate with anonymous methods in C#, as the following example illustrates. (Aby uzyskać wprowadzenie do metod anonimowych, zobacz metody anonimowe).(For an introduction to anonymous methods, see Anonymous Methods.)

using System;
using System.IO;

public class TestAnonymousMethod
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      Action<string, string> concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = delegate(string s1, string s2) { WriteToFile(s1, s2); };
      else
         concat = delegate(string s1, string s2) { WriteToConsole(s1, s2);} ;
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}

Można również przypisać wyrażenie lambda do wystąpienia Action<T1,T2> delegata, jak pokazano w poniższym przykładzie.You can also assign a lambda expression to an Action<T1,T2> delegate instance, as the following example illustrates. (Aby uzyskać wprowadzenie do wyrażeń lambda, zobacz lambda Expressions).(For an introduction to lambda expressions, see Lambda Expressions.)

using System;
using System.IO;

public class TestLambdaExpression
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      Action<string, string> concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = (s1, s2) => WriteToFile(s1, s2);
      else
         concat = (s1, s2) => WriteToConsole(s1, s2);
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}
Imports System.IO

Public Module TestLambdaExpression

   Public Sub Main()
      Dim message1 As String = "The first line of a message."
      Dim message2 As String = "The second line of a message."
      Dim concat As Action(Of String, String)
      
      If Environment.GetCommandLineArgs().Length > 1 Then
         concat = Sub(s1, s2) WriteToFile(s1, s2)
      Else
         concat = Sub(s1, s2) WriteToConsole(s1, s2)
      End If
         
      concat(message1, message2)
   End Sub
  
   Private Function WriteToConsole(string1 As String, string2 As String) As Integer
      Dim message As String = String.Format("{0}{1}{2}", string1, vbCrLf, string2)
      Console.WriteLine(message)
      Return message.Length
   End Function

   Private Function WriteToFile(string1 As String, string2 As String) As Integer
      Dim writer As StreamWriter = Nothing  
      Dim message As String = String.Format("{0}{1}{2}", string1, vbCrLf, string2)
      Dim charsWritten As Integer
      Try
         writer = New StreamWriter(Environment.GetCommandLineArgs()(1), False)
         writer.WriteLine(message)
      Catch
         Console.WriteLine("File write operation failed...")
      Finally
         If writer IsNot Nothing Then 
            writer.Close()
            charsWritten = message.Length
         Else
            charsWritten = 0
         End If
      End Try      
      Return charsWritten
   End Function
End Module

Metody rozszerzania

GetMethodInfo(Delegate)

Pobiera obiekt, który reprezentuje metodę reprezentowaną przez określony delegat.Gets an object that represents the method represented by the specified delegate.

Dotyczy

Zobacz też