# Func<T1,T2,T3,T4,TResult> Delegate

## Definition

Kapselt eine Methode, die über vier Parameter verfügt und einen Wert des Typs zurückgibt, der durch den `TResult`-Parameter angegeben wird.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);``
``public delegate TResult Func<T1,T2,T3,T4,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 ``
``Public Delegate Function Func(Of T1, T2, T3, T4, TResult)(arg1 As T1, arg2 As T2, arg3 As T3, arg4 As T4) As TResult ``

#### Type Parameters

T1

Der Typ des ersten Parameters der Methode, die dieser Delegat kapselt.The type of the first parameter of the method that this delegate encapsulates.

This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
T2

Der Typ des zweiten Parameters der Methode, die dieser Delegat kapselt.The type of the second parameter of the method that this delegate encapsulates.

This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
T3

Der Typ des dritten Parameters der Methode, die dieser Delegat kapselt.The type of the third parameter of the method that this delegate encapsulates.

This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
T4

Der Typ des vierten Parameters der Methode, die dieser Delegat kapselt.The type of the fourth parameter of the method that this delegate encapsulates.

This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
TResult

Der Typ des Rückgabewerts der Methode, die dieser Delegat kapselt.The type of the return value of the method that this delegate encapsulates.

This type parameter is covariant. That is, you can use either the type you specified or any type that is more derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.

#### Parameters

arg1
T1

Der erste Parameter der Methode, die dieser Delegat kapselt.The first parameter of the method that this delegate encapsulates.

arg2
T2

Der zweite Parameter der Methode, die dieser Delegat kapselt.The second parameter of the method that this delegate encapsulates.

arg3
T3

Der dritte Parameter der Methode, die dieser Delegat kapselt.The third parameter of the method that this delegate encapsulates.

arg4
T4

Der vierte Parameter der Methode, die dieser Delegat kapselt.The fourth parameter of the method that this delegate encapsulates.

#### Return Value

TResult

Der Rückgabewert der Methode, die dieser Delegat kapselt.The return value of the method that this delegate encapsulates.

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

## Examples

Im folgenden Beispiel wird veranschaulicht, wie ein Func<T1,T2,TResult> Delegat deklariert und verwendet wird.The following example demonstrates how to declare and use a Func<T1,T2,TResult> delegate. In diesem Beispiel wird eine Func<T1,T2,TResult> Variable deklariert und ihr ein Lambda-Ausdruck zugewiesen, der einen String Wert und einen Int32 Wert als Parameter annimmt.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. Der Lambda-Ausdruck gibt `true` zurück, wenn die Länge des String-Parameters gleich dem Wert des Int32-Parameters ist.The lambda expression returns `true` if the length of the String parameter is equal to the value of the Int32 parameter. Der Delegat, der diese Methode kapselt, wird anschließend in einer Abfrage verwendet, um Zeichen folgen in einem Array von Zeichen folgen zu filtern.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
``````

## Remarks

Mit diesem Delegaten können Sie eine Methode darstellen, die als Parameter übergeben werden kann, ohne explizit einen benutzerdefinierten Delegaten zu deklarieren.You can use this delegate to represent a method that can be passed as a parameter without explicitly declaring a custom delegate. Die gekapselte Methode muss der Methoden Signatur entsprechen, die von diesem Delegaten definiert wird.The encapsulated method must correspond to the method signature that is defined by this delegate. Dies bedeutet, dass die gekapselte Methode über vier Parameter verfügen muss, die jeweils als Wert an Sie übermittelt werden, und dass ein Wert zurückgegeben werden muss.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.

Note

Um auf eine Methode zu verweisen, die über vier Parameter verfügt und `void` (oder in Visual Basic als `Sub` und nicht als `Function`) zurückgibt, verwenden Sie stattdessen den generischen Action<T1,T2,T3,T4> Delegaten.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.

Wenn Sie den Func<T1,T2,T3,T4,TResult> Delegaten verwenden, müssen Sie nicht explizit einen Delegaten definieren, der eine Methode mit vier Parametern kapselt.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. Der folgende Code deklariert z. b. explizit einen generischen Delegaten mit dem Namen `Searcher` und weist der Delegatinstanz einen Verweis auf die IndexOf-Methode zu.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
``````

Im folgenden Beispiel wird dieser Code vereinfacht, indem der Func<T1,T2,T3,T4,TResult> Delegat instanziiert wird, anstatt explizit einen neuen Delegaten zu definieren und ihm eine benannte Methode zuzuweisen.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) _
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
``````

Sie können den Func<T1,T2,T3,T4,TResult> Delegaten mit anonymen Methoden in C#verwenden, wie im folgenden Beispiel veranschaulicht.You can use the Func<T1,T2,T3,T4,TResult> delegate with anonymous methods in C#, as the following example illustrates. (Eine Einführung zu anonymen Methoden finden Sie unter Anonyme Methoden.)(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);
}
}
``````

Sie können einem Func<T1,T2,T3,T4,TResult> Delegaten auch einen Lambda-Ausdruck zuweisen, wie im folgenden Beispiel veranschaulicht.You can also assign a lambda expression to a Func<T1,T2,T3,T4,TResult> delegate, as the following example illustrates. (Eine Einführung in Lambda-Ausdrücke finden Sie unter Lambda -Ausdrücke und Lambda-Ausdrücke.)(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
``````

Der zugrunde liegende Typ eines Lambda-Ausdrucks ist einer der generischen `Func` Delegaten.The underlying type of a lambda expression is one of the generic `Func` delegates. Dadurch ist es möglich, einen Lambda-Ausdruck als Parameter zu übergeben, ohne ihn explizit einem Delegaten zuzuweisen.This makes it possible to pass a lambda expression as a parameter without explicitly assigning it to a delegate. Insbesondere weil viele Methoden von Typen im System.Linq-Namespace über `Func` Parameter verfügen, können Sie diese Methoden einem Lambda-Ausdruck übergeben, ohne explizit einen `Func` Delegaten zu instanziieren.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.

## Extension Methods

 Ruft ein Objekt ab, das die Methode darstellt, die vom angegebenen Delegaten dargestellt wird.Gets an object that represents the method represented by the specified delegate.