Delegates - a 15 minutes quick start tutorial

using System;

namespace CSharpDelegate
{
	class SimpleClass
	{
		public class WorkerClass
		{
			//(1) First method (instance method) referenced by delegate:
			public int InstanceMethod(int nID, string sName)
			{
				int retval=0;
				retval=nID*sName.Length;
				Console.WriteLine("InstanceMethod fired!");
				return retval;
			}

			//(2) Second method (static method) referenced by delegate:
			static public int StaticMethod(int nID, string sName)
			{
				int retval=0;
				retval=nID*sName.Length;
				Console.WriteLine("StaticMethod fired!");
				return retval;
			}
		};

		//(1) That's your delegate - pay attention to delegate's signature. 
		//(2) It has the same signature as the methods to which it references (InstanceMethod and StaticMethod).
		public delegate int SomeDelegate(int nID, string sName);


		[STAThread]
		static void Main(string[] args)
		{

			//PART 1: invoking instance method			
			WorkerClass wr = new WorkerClass();
			SomeDelegate d1 = new SomeDelegate(wr.InstanceMethod); //Associating delegate with wr.InstanceMethod
			Console.WriteLine("Invoking delegate InstanceMethod, return={0}", d1(5, "aaa") ); //Invoking wr.InstanceMethod with input parameters.

			//PART 2: invoking static method
			SomeDelegate d2 = new SomeDelegate(WorkerClass.StaticMethod); //Associating delegate with WorkerClass.StaticMethod (NOTE: "wr" instance is NOT used. The class itself is used!!)
			Console.WriteLine("Invoking delegate StaticMethod, return={0}", d2(5, "aaa") ); //Invoking InstanceMethod with input parameters.

			//PART 3: MultiCAST!
			Console.WriteLine();
			Console.WriteLine("Testing delegate multi-cast..");
			SomeDelegate d3 = (SomeDelegate) Delegate.Combine(d1, d2);
			Console.WriteLine("Invoking delegate(s) d1 AND d2 (multi-cast), return={0} ", d3(5, "aaa") ); //Fire BOTH delegates (d1 AND d2) by firing d3!

			int num_method=d3.GetInvocationList().Length;
			Console.WriteLine("Number of methods referenced by delegate d3: {0}", num_method);

		}
	}
}