Func<T,TResult> Func<T,TResult> Func<T,TResult> Func<T,TResult> Delegate

Definición

generic <typename T, typename TResult>
public delegate TResult Func(T arg);

public delegate TResult Func<in T,out TResult>(T arg);

type Func<'T, 'Result> = delegate of 'T -> 'Result

Public Delegate Function Func(Of In T, Out TResult)(arg As T) As TResult 

Parámetros de tipo

Parámetros

Valor devuelto

TResult

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

Herencia

ObjectObjectObjectObject

DelegateDelegateDelegateDelegate

Func<T,TResult>Func<T,TResult>Func<T,TResult>Func<T,TResult>

Ejemplos

En el ejemplo siguiente se muestra cómo declarar y usar un Func<T,TResult> delegar.The following example demonstrates how to declare and use a Func<T,TResult> delegate. Este ejemplo se declara un Func<T,TResult> variable y se asigna una expresión lambda que convierte los caracteres de una cadena a mayúsculas.This example declares a Func<T,TResult> variable and assigns it a lambda expression that converts the characters in a string to uppercase. El delegado que encapsula este método se pasa a continuación el Enumerable.Select método para cambiar las cadenas en una matriz de cadenas a mayúsculas.The delegate that encapsulates this method is subsequently passed to the Enumerable.Select method to change the strings in an array of strings to uppercase.

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

static class Func
{
   static void Main(string[] args)
   {
      // Declare a Func variable and assign a lambda expression to the  
      // variable. The method takes a string and converts it to uppercase.
      Func<string, string> selector = str => str.ToUpper();
   
      // Create an array of strings.
      string[] words = { "orange", "apple", "Article", "elephant" };
      // Query the array and select strings according to the selector method.
      IEnumerable<String> aWords = words.Select(selector);
   
      // Output the results to the console.
      foreach (String word in aWords)
         Console.WriteLine(word);
   }
}      
/*
This code example produces the following output:
            
   ORANGE
   APPLE
   ARTICLE
   ELEPHANT
*/

Imports System.Collections.Generic
Imports System.Linq

Module Func
   Public Sub Main()
      ' Declare a Func variable and assign a lambda expression to the  
      ' variable. The method takes a string and converts it to uppercase.
      Dim selector As Func(Of String, String) = Function(str) str.ToUpper()
   
      ' Create an array of strings.
      Dim words() As String = { "orange", "apple", "Article", "elephant" }
      ' Query the array and select strings according to the selector method.
      Dim aWords As IEnumerable(Of String) = words.Select(selector)
   
      ' Output the results to the console.
      For Each word As String In aWords
         Console.WriteLine(word)
      Next
   End Sub
End Module
' This code example produces the following output:
'           
'   ORANGE
'   APPLE
'   ARTICLE
'   ELEPHANT

Comentarios

Este delegado se puede usar 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 está definida por 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 un parámetro que se pasa por valor, y debe devolver un valor.This means that the encapsulated method must have one parameter that is passed to it by value, and that it must return a value.

Cuando se usa el Func<T,TResult> delegado, no es necesario definir explícitamente un delegado que encapsula un método con un solo parámetro.When you use the Func<T,TResult> delegate, you do not have to explicitly define a delegate that encapsulates a method with a single parameter. Por ejemplo, el código siguiente declara explícitamente un delegado denominado ConvertMethod y le asigna una referencia a la UppercaseString método a su instancia de delegado.For example, the following code explicitly declares a delegate named ConvertMethod and assigns a reference to the UppercaseString method to its delegate instance.

using System;

delegate string ConvertMethod(string inString);

public class DelegateExample
{
   public static void Main()
   {
      // Instantiate delegate to reference UppercaseString method
      ConvertMethod convertMeth = UppercaseString;
      string name = "Dakota";
      // Use delegate instance to call UppercaseString method
      Console.WriteLine(convertMeth(name));
   }

   private static string UppercaseString(string inputString)
   {
      return inputString.ToUpper();
   }
}

' Declare a delegate to represent string conversion method
Delegate Function ConvertMethod(ByVal inString As String) As String

Module DelegateExample
   Public Sub Main()
      ' Instantiate delegate to reference UppercaseString method
      Dim convertMeth As ConvertMethod = AddressOf UppercaseString
      Dim name As String = "Dakota"
      ' Use delegate instance to call UppercaseString method
      Console.WriteLine(convertMeth(name))
   End Sub

   Private Function UppercaseString(inputString As String) As String
      Return inputString.ToUpper()
   End Function
End Module

En el ejemplo siguiente se simplifica este código creando instancias de la Func<T,TResult> 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<T,TResult> delegate instead of explicitly defining a new delegate and assigning a named method to it.

using System;

public class GenericFunc
{
   public static void Main()
   {
      // Instantiate delegate to reference UppercaseString method
      Func<string, string> convertMethod = UppercaseString;
      string name = "Dakota";
      // Use delegate instance to call UppercaseString method
      Console.WriteLine(convertMethod(name));
   }

   private static string UppercaseString(string inputString)
   {
      return inputString.ToUpper();
   }
}

Module GenericFunc
   Public Sub Main()
      ' Instantiate delegate to reference UppercaseString method
      Dim convertMethod As Func(Of String, String) = AddressOf UppercaseString
      Dim name As String = "Dakota"
      ' Use delegate instance to call UppercaseString method
      Console.WriteLine(convertMethod(name))
   End Sub

   Private Function UppercaseString(inputString As String) As String
      Return inputString.ToUpper()
   End Function
End Module

También puede usar el Func<T,TResult> delegar con métodos anónimos en C#, como se muestra en el ejemplo siguiente.You can also use the Func<T,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 Anonymous
{
   public static void Main()
   {
      Func<string, string> convert = delegate(string s)
         { return s.ToUpper();}; 
         
      string name = "Dakota";
      Console.WriteLine(convert(name));   
   }
}

También puede asignar una expresión lambda a un Func<T,TResult> delegado, como se muestra en el ejemplo siguiente.You can also assign a lambda expression to a Func<T,TResult> delegate, as the following example illustrates. (Para obtener 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 LambdaExpression
{
   public static void Main()
   {
      Func<string, string> convert = s => s.ToUpper();
         
      string name = "Dakota";
      Console.WriteLine(convert(name));   
   }
}

Module LambdaExpression
   Public Sub Main()
      Dim convert As Func(Of String, String) = Function(s) s.ToUpper()
      
      Dim name As String = "Dakota"
      Console.WriteLine(convert(name))  
   End Sub
End Module

El tipo subyacente de una expresión lambda es uno de la clase genérica Func delegados.The underlying type of a lambda expression is one of the generic Func delegates. Esto permite pasar una expresión lambda como un parámetro sin asignar 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, porque muchos métodos de tipos en el System.Linq tiene espacio de nombres Func<T,TResult> parámetros, puede pasar estos métodos de una expresión lambda sin crear explícitamente instancias de un Func<T,TResult> delegar.In particular, because many methods of types in the System.Linq namespace have Func<T,TResult> parameters, you can pass these methods a lambda expression without explicitly instantiating a Func<T,TResult> delegate.

Extension Methods

Se aplica a

Consulte también:

• Expresiones lambda (Guía de programación de C#)Lambda Expressions (C# Programming Guide)
• Lambda (expresiones) (Visual Basic)Lambda Expressions (Visual Basic)
• Delegados (Guía de programación de C#)Delegates (C# Programming Guide)
• Delegados (Visual Basic)Delegates (Visual Basic)