Delegate in C#

1. A delegate is a type that represents references to methods with a particular parameter list and return type. When you instantiate a delegate, you can associate its instance with any method with a compatible signature and return type. You can invoke (or call) the method through the delegate instance.

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DelegateExample
{
    class Program
    {
        static void Main(string[] args)
        {
            PropertyClass objPropertyClass = new PropertyClass("prabakaran");

            objPropertyClass.Changed += DelegateAction;
            objPropertyClass.Changed += DelegateAction;
            objPropertyClass.Changed += DelegateAction;
            objPropertyClass.Name = "pk";


            Console.WriteLine(objPropertyClass.Name);
            Console.ReadLine();
        }

        private static void DelegateAction(object sender, EventArgsClass args)
        {
            Console.WriteLine("oldvalue:" + args.OldValue);
            Console.WriteLine("newvalue:" + args.NewValue);
        }

        //private static void DelegateAction(string oldValue, string newValue)
        //{
        //    Console.WriteLine("oldvalue:" + oldValue);
        //    Console.WriteLine("newvalue:" + newValue);
        //}
    }
}

PropertyClass.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DelegateExample

{

    public class PropertyClass

    {

        public PropertyClass(string name="Default Name")

        {

            Name = name;

        }

        private string _name;

        public string Name 

        { 

            get

            { 

                return _name;

            }

            set

            {

                if (Changed != null)

                {

                    EventArgsClass objEventArgs = new EventArgsClass();

                    objEventArgs.OldValue = _name;

                    objEventArgs.NewValue = value;

                    Changed(this, objEventArgs);

                }

                _name=value;

            }

        }

        public event PropertyChanged Changed;

    }

}

DelegateClass.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DelegateExample

{

    public delegate void PropertyChanged(object sender, EventArgsClass args);

}

EventArgsClass.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DelegateExample

{

    public class EventArgsClass:EventArgs

    {

        public string OldValue { get; set; }

        public string NewValue { get; set; }

    }

}