title: Lightswitch custom contol grid column not refreshing on sorting
body: <p>In my model I have two related fields: <code>integer</code> which is stored in DB and a computed <code>string</code> field which is used for grid. The text displayed is based on the int field's value.</p>
  
  <p>Now the problem with computed fields is they cannot be sorted when used in a grid. My workaround is:</p>
  
  <ol>
  <li>create a custom control, which contains a label</li>
  <li>add it to the grid and set it's DataContext to the integer field</li>
  </ol>
  
  <p>The label inside my UserControl uses a <code>IValueConverter</code> to display the propert text and sorting is still possible, because grid uses the <code>integer</code>.</p>
  
  <p>Unfortunately when I click the header although the grid's data does get sorted, the custom controls' text doesn't refresh. </p>
  
  <p>What should I do?</p>