title: preventing row change in datagrid
body: <p>I have researched this and am stumped: I have a WPF DataGrid, and using an MVVM model.  I want to, under certain circumstances, prevent the ability to change a row in the DataGrid.  I have researched this and have tried techniques like the one found <a href="http://social.msdn.microsoft.com/Forums/en/wpf/thread/bb0a6458-b073-433c-b98b-4b18aa31e0f3" rel="noreferrer">here</a>.</p>
  
  <p>In practice, this works, however there is an undesirable 'flicker' (it selects the clicked row for a moment then goes back to the previous selection), while this is a close solution I wish there was a more elegant way such as preventing the row change at all in the first place.  </p>
  
  <p>I am surprised there is not a SelectionChanging or BeforeSelectionChanged so I could cancel the event from firing; and forcibly preventing the index change in my view model does not seem to make any difference. </p>
  
  <p>How can I do this? </p>
  
  <p>Thank you. </p>