Func<T1,T2,T3,T4,TResult> Delegado

Definición

Encapsula un método que tiene cuatro parámetros y devuelve un valor del tipo especificado por el parámetro TResult.Encapsulates a method that has four parameters and returns a value of the type specified by the TResult parameter.

generic <typename T1, typename T2, typename T3, typename T4, typename TResult>
public delegate TResult Func(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
public delegate TResult Func<in T1,in T2,in T3,in T4,out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
type Func<'T1, 'T2, 'T3, 'T4, 'Result> = delegate of 'T1 * 'T2 * 'T3 * 'T4 -> 'Result
Public Delegate Function Func(Of In T1, In T2, In T3, In T4, Out TResult)(arg1 As T1, arg2 As T2, arg3 As T3, arg4 As T4) As TResult 

Parámetros de tipo

T1

Tipo del primer parámetro del método que este delegado encapsula.The type of the first parameter of the method that this delegate encapsulates.

T2

Tipo del segundo parámetro del método que este delegado encapsula.The type of the second parameter of the method that this delegate encapsulates.

T3

Tipo del tercer parámetro del método que este delegado encapsula.The type of the third parameter of the method that this delegate encapsulates.

T4

Tipo del cuarto parámetro del método que este delegado encapsula.The type of the fourth parameter of the method that this delegate encapsulates.

TResult

Tipo del valor devuelto del método que este delegado encapsula.The type of the return value of the method that this delegate encapsulates.

Parámetros

arg1

Primer parámetro del método que este delegado encapsula.The first parameter of the method that this delegate encapsulates.

arg2

Segundo parámetro del método que este delegado encapsula.The second parameter of the method that this delegate encapsulates.

arg3

Tercer parámetro del método que este delegado encapsula.The third parameter of the method that this delegate encapsulates.

arg4

Cuarto parámetro del método que este delegado encapsula.The fourth parameter of the method that this delegate encapsulates.

Valor devuelto

TResult

Valor devuelto del método que este delegado encapsula.The return value of the method that this delegate encapsulates.

Herencia
Func<T1,T2,T3,T4,TResult>

Ejemplos

En el ejemplo siguiente se muestra cómo declarar y usar Func<T1,T2,TResult> un delegado.The following example demonstrates how to declare and use a Func<T1,T2,TResult> delegate. En este ejemplo se declara Func<T1,T2,TResult> una variable y se le asigna una expresión lambda que toma un String valor y un Int32 valor como parámetros.This example declares a Func<T1,T2,TResult> variable and assigns it a lambda expression that takes a String value and an Int32 value as parameters. La expresión lambda devuelve true si la longitud String del parámetro es igual Int32 al valor del parámetro.The lambda expression returns true if the length of the String parameter is equal to the value of the Int32 parameter. El delegado que encapsula este método se usa posteriormente en una consulta para filtrar cadenas en una matriz de cadenas.The delegate that encapsulates this method is subsequently used in a query to filter strings in an array of strings.

using System;
using System.Collections.Generic;
using System.Linq;

public class Func3Example
{
   public static void Main()
   {
      Func<String, int, bool> predicate = (str, index) => str.Length == index;

      String[] words = { "orange", "apple", "Article", "elephant", "star", "and" };
      IEnumerable<String> aWords = words.Where(predicate).Select(str => str);

      foreach (String word in aWords)
         Console.WriteLine(word);
   }
}
Imports System.Collections.Generic
Imports System.Linq

Public Module Func3Example

   Public Sub Main()
      Dim predicate As Func(Of String, Integer, Boolean) = Function(str, index) str.Length = index

      Dim words() As String = { "orange", "apple", "Article", "elephant", "star", "and" }
      Dim aWords As IEnumerable(Of String) = words.Where(predicate)

      For Each word As String In aWords
         Console.WriteLine(word)
      Next   
   End Sub
End Module

Comentarios

Puede usar este delegado para representar un método que se puede pasar como un parámetro sin declarar explícitamente un delegado personalizado.You can use this delegate to represent a method that can be passed as a parameter without explicitly declaring a custom delegate. El método encapsulado debe corresponder a la firma del método que define este delegado.The encapsulated method must correspond to the method signature that is defined by this delegate. Esto significa que el método encapsulado debe tener cuatro parámetros, cada uno de los cuales se le pasa por valor y que debe devolver un valor.This means that the encapsulated method must have four parameters, each of which is passed to it by value, and that it must return a value.

Nota

Para hacer referencia a un método que tiene cuatro parámetros void y devuelve (o en Visual Basic, que se declara Sub como un en lugar Functionde como), use Action<T1,T2,T3,T4> el delegado genérico en su lugar.To reference a method that has four parameters and returns void (or in Visual Basic, that is declared as a Sub rather than as a Function), use the generic Action<T1,T2,T3,T4> delegate instead.

Cuando se usa el Func<T1,T2,T3,T4,TResult> delegado, no es necesario definir explícitamente un delegado que encapsula un método con cuatro parámetros.When you use the Func<T1,T2,T3,T4,TResult> delegate, you do not have to explicitly define a delegate that encapsulates a method with four parameters. Por ejemplo, el código siguiente declara explícitamente un delegado genérico denominado Searcher y asigna una referencia IndexOf al método a su instancia de delegado.For example, the following code explicitly declares a generic delegate named Searcher and assigns a reference to the IndexOf method to its delegate instance.

using System;

delegate int Searcher(string searchString, int start, int count, 
                         StringComparison type);
                         
public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Searcher finder = title.IndexOf;
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters, 
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.", 
                              position, title);
         }
      } while (position > 0);
   }
}
Delegate Function Searcher(searchString As String, _
                           start As Integer,  _
                           count As Integer, _
                           type As StringComparison) As Integer

Module DelegateExample
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim position As Integer = 0
      Dim finder As Searcher = AddressOf title.IndexOf
      Do
         Dim characters As Integer = title.Length - position
         position = finder("the", position, characters, _
                         StringComparison.InvariantCultureIgnoreCase) 
         If position >= 0 Then
            position += 1
            Console.WriteLine("'The' found at position {0} in {1}.", _
                              position, title)
         End If   
      Loop While position > 0   
   End Sub
End Module

En el ejemplo siguiente se simplifica este código creando una instancia Func<T1,T2,T3,T4,TResult> del delegado en lugar de definir explícitamente un nuevo delegado y asignarle un método con nombre.The following example simplifies this code by instantiating the Func<T1,T2,T3,T4,TResult> delegate instead of explicitly defining a new delegate and assigning a named method to it.

using System;

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Func<string, int, int, StringComparison, int> finder = title.IndexOf;
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters, 
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.", 
                              position, title);
         }
      } while (position > 0);
   }
}
Module DelegateExample
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim position As Integer = 0
      Dim finder As Func(Of String, Integer, Integer, StringComparison, Integer) _
                    = AddressOf title.IndexOf
      Do
         Dim characters As Integer = title.Length - position
         position = finder("the", position, characters, _
                         StringComparison.InvariantCultureIgnoreCase) 
         If position >= 0 Then
            position += 1
            Console.WriteLine("'The' found at position {0} in {1}.", _
                              position, title)
         End If   
      Loop While position > 0   
   End Sub
End Module

Puede usar el Func<T1,T2,T3,T4,TResult> delegado con métodos anónimos en C#, como se muestra en el ejemplo siguiente.You can use the Func<T1,T2,T3,T4,TResult> delegate with anonymous methods in C#, as the following example illustrates. (Para obtener una introducción a los métodos anónimos, consulte métodos anónimos).(For an introduction to anonymous methods, see Anonymous Methods.)

using System;

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Func<string, int, int, StringComparison, int> finder = 
           delegate(string s, int pos, int chars, StringComparison type) 
           { return title.IndexOf(s, pos, chars, type); };
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters, 
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.", 
                              position, title);
         }
      } while (position > 0);
   }
}

También puede asignar una expresión lambda a un Func<T1,T2,T3,T4,TResult> delegado, como se muestra en el ejemplo siguiente.You can also assign a lambda expression to a Func<T1,T2,T3,T4,TResult> delegate, as the following example illustrates. (Para ver una introducción a las expresiones lambda, vea expresiones lambda y expresiones lambda).(For an introduction to lambda expressions, see Lambda Expressions and Lambda Expressions.)

using System;

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Func<string, int, int, StringComparison, int> finder = 
           (s, pos, chars, type) => title.IndexOf(s, pos, chars, type); 
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters, 
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.", 
                              position, title);
         }
      } while (position > 0);
   }
}
Module DelegateExample
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim position As Integer = 0
      Dim finder As Func(Of String, Integer, Integer, StringComparison, Integer) _
                    = Function(s, pos, chars, type) _
                    title.IndexOf(s, pos, chars, type)
      Do
         Dim characters As Integer = title.Length - position
         position = finder("the", position, characters, _
                         StringComparison.InvariantCultureIgnoreCase) 
         If position >= 0 Then
            position += 1
            Console.WriteLine("'The' found at position {0} in {1}.", _
                              position, title)
         End If   
      Loop While position > 0   
   End Sub
End Module

El tipo subyacente de una expresión lambda es uno de los delegados genéricos Func .The underlying type of a lambda expression is one of the generic Func delegates. Esto hace posible pasar una expresión lambda como parámetro sin asignarla explícitamente a un delegado.This makes it possible to pass a lambda expression as a parameter without explicitly assigning it to a delegate. En concreto, dado que muchos métodos de tipos en System.Linq el espacio Func de nombres tienen parámetros, puede pasar estos métodos a una expresión lambda sin crear Func explícitamente instancias de un delegado.In particular, because many methods of types in the System.Linq namespace have Func parameters, you can pass these methods a lambda expression without explicitly instantiating a Func delegate.

Métodos de extensión

GetMethodInfo(Delegate)

Obtiene un objeto que representa el método representado por el delegado especificado.Gets an object that represents the method represented by the specified delegate.

Se aplica a

Consulte también: