title: Telerik RadTextBox with exclamation mark
body: <p>The RadTextBox in this example shows an exclamation mark icon (!) if no input is available. The example on this page shows how to use RadInputManager to extend normal asp textboxes to have the exclamation mark:
  <a href="http://demos.telerik.com/aspnet-ajax/input/examples/radinputmanager/firstlook/defaultcs.aspx" rel="nofollow noreferrer">http://demos.telerik.com/aspnet-ajax/input/examples/radinputmanager/firstlook/defaultcs.aspx</a></p>
  
  <p>However, there doesn't seem to be an example as to how this exclamation mark can be displayed if I am already using a RadTextBox... Is this feasible?</p>
  
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  <p>It's worth noting that I am interested in this because it's cleaner than writing out an error message... Any other technique (ie highlighting the empty text box etc.) would work equally well for me.</p>