We used delegate a lot in some or other way. Like as we know, the event base model that we use in windows as web programming, is based on delegate only. I am in the habit of using delegates often. In last few days, I found a very elegent way to use the delegate.I was in the habit of of using only generic delegates that allows us type safety and lot more flexibility.

In our traditional programming, we use the delegate as in the following steps.

1. Declaring the delegate
2. Creating object of the delegate and assigning it to appropriate function
3. Calling the delegate

Lets see the code

 public class Program
    {
        //Declaring an delegate
        public delegate void MyDelegate<R, S>(R r, S s);
        public static void Main(string[] args)
        {
            //Creating an Action variable and assigning it to a function
            MyDelegate<int, int> m1 = Multiply;
            //Calling the method
            m1(3, 4);
            Console.ReadKey();
        }

        public static void Multiply(int i, int j)
        {
            Console.WriteLine(i * j);
        }
    }

.NET 2.0 introcuced one generic delegate Action which takes a single parameter and returns nothing. Its declaration is
–Public delegate void Action<T1>(T1 t1) // Takes 1 parameter and returns nothing
This is a very much elegatent way to use the delegate.

And C# 3.0, introduced 4 delegates which are as

1. Public delegate void Action() // Takes no parameter and returns nothing
2. Public delegate void Action<T1,T2>(T1 t1,T2 t2) // Takes 2 parameters and returns nothing
3. Public delegate void Action<T1,T2,T3>(T1 t1,T2 t2,T3 t3) // Takes 3 parameters and returns nothing
4. Public delegate void Action<T1,T2,T3,T4>(T1 t1,T2 t2,T3 t3),T4 t4) // Takes 4 parameters and returns nothing

Lets see them running

public class Program
{
public static void Main(string[] args)
{
//Creating an Action variable and assigning it to a function
Action myAction = Multiply;
//Calling the method
myAction(3, 4);

//Also can be called as
myAction.Invoke(3, 4);
}

public static void Multiply(int i,int j)
{
Console.WriteLine(i * j);
}
}

As from the code, we can also see that Action delegate also provide a method invoke to call the method.

These Action delegate also can be used with Anonymous Methods as

public class Program
{
public static void Main(string[] args)
{
//Creating an Action variable and assigning it to a function
Action myAction = delegate(int i, int j) { Console.WriteLine(i * j); };
//Calling the method
myAction(3, 4);

Console.ReadKey();
}
}

Also can be used with lambda function. Lets see

public class Program
    {
        public static void Main(string[] args)
        {
            //Creating an Action variable and assigning it to a function
            Action<int> myAction = s => Console.WriteLine(s * 5);
            //Calling the method
            myAction(3);

            Console.ReadKey();
        }
    }

So code delegently and efficiently.

Note: The ForEach and ForEach<T> methods each take an Action<T> delegate as a parameter. The method encapsulated by the delegate allows us to perform an action on each element in the array or list.

Happy .Neting….

Cheers,
Brij