Q: How to know which button click is fired in c#
Ans:
   If sender Is Button1 Then
      s = "button1"
   ElseIf sender Is Button2 Then
      s = "button2"
   End If

Q: How to call one button click event in another
Ans:
  protected void btnSaveChanges_Click(object sender, EventArgs e)
  {
    btnContinue_Click(sender, e);
  }