title: Windows Phone Multi Line Text Box
body: <p>I want to create a UI element that behaves approximately like the native WP SMS App's input text box.</p>
  
  <p>Basically it should </p>
  
  <ul>
  <li>start as a single line text box</li>
  <li>when my text reaches the end of the first line, it should expand one line to encompass it</li>
  <li>this needs to go to a Max Height of 5 line (where a line = the text box's Height value)</li>
  <li>once my text requires more than 5 lines, the text box should stop expanding and a vertical scroll bar should appear </li>
  </ul>
  
  <p>Any suggestions on how I can do this? I'd rather not use events to see how much text I've entered and expand/compress the text box based on that, or create a new UI element from scratch.</p>
  
  <p>If it helps, I've got access to Telerik's RAD Controls for Windows Phone (RadTextBox).</p>