title: Trigger Condition when Not an Empty String
body: <p>We can check some control's string property which has been empty like following code:</p>
  <pre><code>&lt;Trigger SourceName=&quot;atCaption&quot; Property=&quot;Text&quot; Value=&quot;{x:Static sys:String.Empty}&quot;&gt;
      &lt;Setter TargetName=&quot;imgBack&quot; Property=&quot;Margin&quot; Value=&quot;0&quot;/&gt;
      &lt;Setter TargetName=&quot;atCaption&quot; Property=&quot;Margin&quot; Value=&quot;0&quot;/&gt;
  &lt;/Trigger&gt;
  </code></pre>
  <p>but,  how can one define a condition which is based on a 'not empty' string?</p>
  <pre><code>&lt;!--unfortunately, can't accept '!=' operator in xaml.--&gt;
  &lt;Trigger SourceName=&quot;atCaption&quot; Property=&quot;Text&quot; Value!=&quot;{x:Static sys:String.Empty}&quot;&gt;
      &lt;Setter TargetName=&quot;imgBack&quot; Property=&quot;Margin&quot; Value=&quot;0&quot;/&gt;
      &lt;Setter TargetName=&quot;atCaption&quot; Property=&quot;Margin&quot; Value=&quot;0&quot;/&gt;
  &lt;/Trigger&gt;
  </code></pre>