title: How do I add text to a textbox? Not replace
body: <p>I'd like to know how to add text to a textbox by the use of an event, for example the click of a button.</p>
  
  <p>Now when I say add I literally mean add, not replace.</p>
  
  <p>Not <code>TextBox1.Text = ""</code> because all that does it change all the text in the textbox to whatever is in the quotes, I want to add text not replace it so for example if I had "ABC" typed into my textbox and I want to add the letter "D" to it without replacing the whole text what would I have to do? </p>
  
  <p>Thanks in advance. </p>