The Click Event for Buttons

The Click Event for Buttons

The click event gets activated when a button is clicked on. Examine the default code for a button:
private void button1_Click(object sender, EventArgs e)
{
}
In between the round brackets, we have this:

object sender, EventArgs e

The object keyword refers to the object which activated the event, a button in this case. This is being placed in a variable called sender. You can test this for yourself.
Start a new project. Add a button to your new form and double click it. Place the following code between the curly brackets:

MessageBox.Show( sender.ToString() );

We're just using the ToString method on the sender variable. Run your programme and click the button. You should see this:

The Message is displaying which object was the sender of the event, as well as displaying the Text property of the sender: the button with the Text "button1".
The other argument in between the round brackets was this:

EventArgs e

EventArgs is a class. It's short for event arguments, and tells you which events was raised. The letter "e" sets up a variable to use this class. If you change your line of code to this:

MessageBox.Show( e.ToString() );

the message box will then display the following: