Multicast Delegate in C#

Hello Everyone, I talked about delegate in my last article. In this article we will talk about multicast delegate.

A Delegate is a type variable that holds the reference of a method and multicast delegate can holds the reference of multiple methods. So basically it's kind of linked list of methods. When we execute the multicast delegate then all the methods which are associated with the multicast delegate will execute in sequence.

How can we create a multicast delegate ?

There is no difference in creation of Delegate and Multicast Delegate. It's just we can associate multiple methods with the same delegate.

 Now the question is how can we associate  multiple methods to a delegate ?

There are two ways of associating multiple methods  -

Delegate.Combine(myDelA, myDelB);

Or

myDelA += MethodB;


Let's see the example -

So now question is How multicast delegate reference to the methods and invoke it ?

There is a method exposed in delegate from which we can fetch the invocation list
and that list returns the collection of all the associated delegates.

public delegate int myDel();

        static void Main(string[] args)
        {
            myDel multiCast = MethodC;
            multiCast += MethodD;

            foreach (myDel del in multiCast.GetInvocationList())
            {
                del.Invoke();
            }
        }

        static int MethodC()
        {
            Console.WriteLine("Executing method C.");
            return 1;
        }

        static int MethodD()
        {
            Console.WriteLine("Executing method D.");
            return 1;
        }

So in the above example I have not called invoke method of delegate directly. Instead of fetching all the method info from GetInvocationList() and invoking it one by one. This is the way .Net framework calls the method in sequential way.

Let's say if some of the method throws exception then how multicast delegate handles that situation ?

Have a look on below Example this is the answer of the question -

public delegate int myDel();

        static void Main(string[] args)
        {
            myDel multiCast = MethodC;
            multiCast += MethodD;
            //If you will call this. This will throw exception
            //multiCast.Invoke();

            foreach (myDel del in multiCast.GetInvocationList())
            {
                try
                {
                    del.Invoke();
                }
                catch (Exception)
                {
                    //Handled
                }
            }
        }

        static int MethodC()
        {
            try
            {
                return 1;
            }
            catch (Exception ex)
            {
                return 0;
            }

            throw new Exception();
        }

        static int MethodD()
        {
            Console.WriteLine("Executing method D.");
            return 1;
        }

Hope you like reading this article. Please inbox me in case of any confusion.

Happy Coding :)