title: RelayCommand vs EventToCommand
body: <p>I'm little confused about <code>RelayCommand</code> and <code>EventToCommand</code> in Mvvmlight.
  It seems that <code>EventToCommand</code> handle the <code>EventTrigger</code> and call a <code>RelayCommand</code> to do job.
  Such as:</p>
  
  <pre><code> &lt;i:Interaction.Triggers&gt;
          &lt;i:EventTrigger x:Uid="i:EventTrigger_1" EventName="MouseLeftButtonUp"&gt;
              &lt;cmd:EventToCommand x:Uid="cmd:EventToCommand_1" Command="{Binding Form_MouseLeftButtonUpCommand}" PassEventArgsToCommand="True"/&gt;
          &lt;/i:EventTrigger&gt;
      &lt;/i:Interaction.Triggers&gt;
  </code></pre>
  
  <p>Is my understanding correct?</p>
  
  <p>So, can we use <code>RelayCommand</code> directly with <code>EventTrigger</code>, no need to use <code>EventToCommand</code>?</p>
  
  <p>Thanks for your help!</p>