title: Track closing event of windows form with validation of button clicked in the form
body: <p>I have a form which contains a close button (there are many control in the form, but I am concerning about the close event) and a save button. </p>
  
  <p>If a form have value in certain text box (say TextBox1),</p>
  
  <p>Then I want to validate that the save button is clicked before closing the form (whether close button or the 'X' button at top is pressed). </p>
  
  <p>But if there is no value in that text box or the form is just initialized and user just want to close the form, it simply closes the form. How to perform this validation.</p>