title: TextBox KeyDown Trigger Event not working for Backspace and Delete key
body: <p>I have a Textbox and for that textbox I have attached a keydown event. Everything is working fine but I just noticed that when i'm pressing the 'Backspace' and 'Delete' Key, the binding command is not being called.</p>
  
  <p><strong>My View xaml file :-</strong></p>
  
  <pre><code>&lt;TextBox x:Name="textBox" Width="500" Text="{Binding TextBoxText, UpdateSourceTrigger=PropertyChanged}"&gt;
  &lt;i:Interaction.Triggers&gt;                
      &lt;i:EventTrigger EventName="KeyDown"&gt;  
          &lt;cmd:EventToCommand Command="{BindingPath=TextBoxKeyDownEvent}" PassEventArgsToCommand="True" /&gt;                
      &lt;/i:EventTrigger&gt;            
  &lt;/i:Interaction.Triggers&gt;
  &lt;/TextBox&gt;
  </code></pre>
  
  <p><strong>My ViewModel cs file :-</strong></p>
  
  <pre><code>    //TextBox Key Down Event Handler
      private DelegateCommand _textBoxKeyDownEvent;
      public ICommand TextBoxKeyDownEvent
      {
          get
          {
              if (_textBoxKeyDownEvent == null)
              {
                  _textBoxKeyDownEvent = new DelegateCommand(TextBoxKeyDownEventHandler);
              }
              return _textBoxKeyDownEvent;
          }
          set { }
      }
  </code></pre>
  
  <p>Can somebody give me some suggestion</p>