What is Event handling in C#.net and How it is work

1)The Event handling is nothing but  executing some code whenever the user performs an action.
2)The Required code is to be return in a special method the method is that called as "Event handler".
3)The Event handler should be define in the Form class.
Syntax:
 private void btnAdd_Click(object sender, EventArgs e)
        {
              //write your code here
        } 
Note1:  1)"btnAdd"  is the control name
             2)"Click"       is the Event name
Note2:  1)sender: sender represents the control based on which the   Events raised.
             2)e: The "e" contains  some additional info about the Event for example in mouse Click event the position of the mouse will be represented  where it is clicked.

Example:
Steps:
1)Goto button control properties
2)Goto events
3)Double click on "Mouse Enter Event"
4)write below code

 private void button1_MouseEnter(object sender, EventArgs e)
        {
            button1.BackColor = Color.DarkRed;
            button1.ForeColor = Color.PowderBlue;
        }

shown below figures:

.Above figure shows form with button

 .Above figure shows form with Mouse Enter event fire(change the button color)
I hope this code will help you.