Func, Action and lambda

lambda expression are often used with Func and Action delegates.

Func and Action are predefined delegates with generic parameters.

 
delegate TResult Func <out TResult>  ();
delegate TResult Func <in T, out TResult>  (T arg);
delegate TResult Func <in T1, in T2, out TResult>  (T1 arg1, T2 arg2);

... and so on, up to T16

delegate void Action  ();
delegate void Action <in T>  (T arg);
delegate void Action <in T1, in T2>  (T1 arg1, T2 arg2);

... and so on, up to T16

Here is an example of how use to use Func to create a lambda expression.

 
using System;


class Program
{
    public static void Main()
    {

        Func<int, int> sqr = x => x * x;

        Console.WriteLine(sqr(3));
    }
}

The output:


9
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