title: Wpf UI does not update
body: <p>I have a wpf mvvm application.
  There is a button in the view and it is bound to a command in the view model.
  The function CanExecute of this command returns the value of some bool property</p>
  
  <pre><code>private bool Command1CanExecute()
  {
      return IsConnected;
  }
  </code></pre>
  
  <p>When the property is changed, the button should become disabled but it's doesn't happened until I click somewhere in UI.
  The solution I have thought about (and it works :) ) is to run </p>
  
  <pre><code>  CommandManager.InvalidateRequerySuggested();
  </code></pre>
  
  <p>each second (Dispatcher timer can do it).</p>
  
  <p>Is there another, more elegant solution for my problem?
  Thank you.</p>
  
  <p>Matvey.</p>