title: WPF TextBox focus "sticking" after disabling and enabling
body: <p>I have a TextBox in a Grid that has InputBindings such that when I hit return, a search is performed in a background thread.</p>
  
  <p>The <code>IsEnabled</code> property of the TextBox is bound to a <code>bool</code> property in my ViewModel called IsSearching, which is true while the background thread is running (I use a converter to negate the value).</p>
  
  <p>I type in TextBox and hit enter, starting the search and disabling the TextBox. When the background thread completes, the TextBox is enabled, however the focus is messed up:</p>
  
  <p>The caret is still inside the TextBox however it does not blink, and I am unable to type. I believe the TextBox has focus, but not "<code>KeyboardFocus</code>".</p>
  
  <p>Can anyone tell me how to resolve this?</p>