title: Whats the best way/event to use when testing if the textbox text has finished a change of text
body: <p>using winforms, c#, vs 2008</p>
  
  <p>So i have textbox1, textbox2 and textbox3 on a winforms.</p>
  
  <p>Textbox3.text = textbox1.text + textbox2.text.</p>
  
  <p>I need textbox3 to be updated whenever the contents of textbox1 and textbox2 have been changed either manually or programmatic.</p>
  
  <p>The problem is if i use textbox textchanged event it keeps firing as one types in the textbox. I need a way to call my method to fill textbox3 after either tb1 or tb2 have been FINISHED changing programmaticly or via key entry, and not fire everytime a letter of text is entered.</p>
  
  <p>How can I have TextBox3 update only when tb1 or tb2 have <strong>finished</strong> changing?</p>