How to add Custom Event Handler for UDTs (User Defined Types)

Today one of my friend asked me how to add custom events to our custom class.With simple example i explained to him then  I thought i can blog his question and Answer. Here is the example i used

Suppose let say we have UDT Called  Contact with the following properties Name, Phone , Email, and Address. suppose we want to notified if some one changes Contact Phone number property .

First let us define UDT as C# Class.

public class Contact
    {
        private string phone = string.Empty;
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Address { get; set; }

        // Define the event for Phone number change.
        public event EventHandler PhoneChanged;
        public string Phone 
        { 
            get
            {
                return phone;
            }
            set
            {
                this.phone = value;
                if (this.PhoneChanged != null) //Check to see event is not null
                    this.PhoneChanged(this , new EventArgs());
            }
        }

       
    }

Now let see how we can invoke this event from code.

namespace ConsoleApplication6
{
    class Program
    {
        static void Main(string[] args)
        {
            Contact c = new Contact();
            c.PhoneChanged += new EventHandler(c_PhoneChanged);
            c.FirstName = "Sreeni";
            c.LastName = "Ramadurai";
            c.Address= "123 Main Street";
            c.Phone = "214-499-2837"; // Here i am setting (changing) the phone number.
            c.PhoneChanged+=new EventHandler(c_PhoneChanged);
        }

        static void c_PhoneChanged(object sender, EventArgs e)
        {
            Console.WriteLine("PhoneChanged");

            Contact c = (Contact)sender; //we need to cast here
            Console.WriteLine(c.Phone ); // Display the phone number.
        }
    }

Nandri(Thanks)

SreenivasaRagavan.