Func<T1, T2, T3, TResult> Delegate

Parameters

arg1

Type: T1

The first parameter of the method that this delegate encapsulates.

arg2

Type: T2

The second parameter of the method that this delegate encapsulates.

arg3

Type: T3

The third parameter of the method that this delegate encapsulates.

Return Value

The return value of the method that this delegate encapsulates.

Type Parameters

in T1

The type of the first parameter of the method that this delegate encapsulates.

in T2

The type of the second parameter of the method that this delegate encapsulates.

in T3

The type of the third parameter of the method that this delegate encapsulates.

out TResult

The type of the return value of the method that this delegate encapsulates.

You can use this delegate to represent a method that can be passed as a parameter without explicitly declaring a custom delegate. The encapsulated method must correspond to the method signature that is defined by this delegate. This means that the encapsulated method must have three parameters, each of which is passed to it by value, and that it must return a value.

Note
To reference a method that has three 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> delegate instead.

When you use the Func<T1, T2, T3, TResult> delegate, you do not have to explicitly define a delegate that encapsulates a method with three parameters. For example, the following code explicitly declares a generic delegate named ParseNumber and assigns a reference to the Parse method to its delegate instance.

The following example simplifies this code by instantiating the Func<T1, T2, T3, TResult> delegate instead of explicitly defining a new delegate and assigning a named method to it.

You can use the Func<T1, T2, T3, TResult> delegate with anonymous methods in C#, as the following example illustrates. (For an introduction to anonymous methods, see Anonymous Methods (C# Programming Guide).)

using System;
using System.Globalization;

public class Anonymous
{
   public static void Main()
   {
      string numericString = "-1,234";
      Func<string, NumberStyles, IFormatProvider, int> parser = 
           delegate(string s, NumberStyles sty, IFormatProvider p) 
           { return int.Parse(s, sty, p); };
      Console.WriteLine(parser(numericString, 
                        NumberStyles.Integer | NumberStyles.AllowThousands, 
                        CultureInfo.InvariantCulture));
   }
}

You can also assign a lambda expression to a Func<T1, T2, T3, TResult> delegate, as the following example illustrates. (For an introduction to lambda expressions, see Lambda Expressions (Visual Basic) and Lambda Expressions (C# Programming Guide).)

The underlying type of a lambda expression is one of the generic Func delegates. This makes it possible to pass a lambda expression as a parameter without explicitly assigning it to a delegate. 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.