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.

When you use the Func`4 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 int.Parse(string, System.Globalization.NumberStyles, IFormatProvider) method to its delegate instance.

code reference: System.Func~4#1

The following example simplifies this code by instantiating the Func`4 delegate instead of explicitly defining a new delegate and assigning a named method to it.

code reference: System.Func~4#2

You can use the Func`4 delegate with anonymous methods in C#, as the following example illustrates. (For an introduction to anonymous methods, see Anonymous Methods (C# Programming Guide).)

code reference: System.Func~4#3

You can also assign a lambda expression to a Func`4 delegate, as the following example illustrates. (For an introduction to lambda expressions, see Lambda Expressions and Lambda Expressions (C# Programming Guide).)

code reference: System.Func~4#4

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.

Namespace: System
Assembly: System.Core (in System.Core.dll)
Assembly Versions: 3.5.0.0