Button click events question?

hello every one:
  i have a question about button click events.
  Some one you konw they use
Like: (1)  btnAddUser.Click+=new EventHandler(btnAddUser_Click);  // onPageLoad
 and then . 
  private void btnAddUser_Click(Object sender,EventArgs e)
{
  //doSoming...
}
(2) Some one use button events >
UI point directly above the button in the method of generating action in writing.
.I want to konw ,
The first one way and the second means the difference between
(My english is poor ,I do not joke. 3ks ...)