Predefined .net delegates Action, Func, Predicate

There are some predefined delegates provided by .net those makes code more simpler to write.

1. Predicate: This delegate takes one input matches some condition and returns boolean value. This delegate is used to pass in functions of collection to match a condition, based on condition function returns collection items.
   ex.      Predicate<string> delPredicate = X => X.Length < 4;
   string myName = lstNames.Find(delPredicate);
   
2. Action: This delegate takes one input and no output. This is used when out put not required and doing some operation with input inside as well.
   ex.  Action<string> delAction = G => Console.WriteLine(G);
   
3. Func: This delegate has 17 overload methods, it returns 1 output and can take 1 to 16 inputs. This is used when we need output of some operation with providing 1 to 16 input parameters.
   Last parameter can be passed as output parameter if required.
   ex1     Func<int, int, int> delMulFunc = (x, y) => x * y;
   ex2     Func<int, double> delTriangleArea = L => 3.14 * L * L;

Examples

class Program

{

    delegate int delAdd(int a, int b);

    static void Main(string[] args)

    {

    //Normal delegate

    delAdd delA = AddNum;

    int c = delA(50, 60);

    Console.WriteLine("Normal delegate: Value of c -" + c.ToString());

    //Lamda expression

    delAdd delLamda = (x,y) => x - y;

    int z = delLamda(70, 20);

    Console.WriteLine("Lamda expression: Value of z -" + z.ToString());

    //Ready made delegate Func

    Func<int, int, int> delMulFunc = (x, y) => x * y;

    int k = delMulFunc(20, 30);

    Console.WriteLine("Func: two input, Value of k -" + k.ToString());

    Func<int, double> delTriangleArea = L => 3.14 * L * L;

    double area = delTriangleArea(20);

    Console.WriteLine("Func: one input, Value of area :" + area.ToString());

    //Ready made delegate Action

    Action<string> delAction = G => Console.WriteLine(G);

    delAction("Action: Hello IT");

    //Ready made delegate Predicate

    Predicate<string> delPredicate = X => X.Length < 4;

    //use

    List<string> lstNames = new List<string> { "Ramu", "Raghu", "Raj", "Rajeev", "Ram" };

    string myName = lstNames.Find(delPredicate);

    Console.WriteLine("Predicate: Value of myName :" + myName);

    Console.ReadLine();

    }

    static int AddNum(int i, int j)

    {

        return i + j;

    }

}