title: PreviewTextInput is fired when the checkbox has focus/Handling the PreviewTextInput in Main window and not allowing child control to steal characters
body: <p>I have the following code. The window has a textbox and a checkbox. If I have focus on the anything other than checkbox and type something like 123-456 then for each character <code>PreviewKeyDown</code> and <code>PreviewTextInput</code> are firing. </p>
  
  <p>But if I have the focus to checkbox and then type 123-456 then the <code>PreviewKeyDown</code> is fired for all the characters whereas <code>PreviewTextInput</code> fires only for 123456 and doesn't fire for <kbd>-</kbd>. The hyphen is being handled by the checkbox and not getting passed to <code>PreviewTextInput</code>. Is there a way to get the hyphen to <code>PreviewTextInput</code>?</p>
  
  <pre><code>public Window1()
  {
      InitializeComponent();
      TextCompositionManager.AddTextInputHandler(this, new TextCompositionEventHandler(Window_PreviewTextInput));
  }
  
  private void Window_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
  {
  
  }
  
  private void Window_PreviewTextInput(object sender, TextCompositionEventArgs e)
  {
  }
  </code></pre>