Problem with operator?
<p>I am writing following code:</p>

<pre><code>_normDoc = value as NormDoc;
  if(_normDoc != null)
   {
     ucRusKazTextBoxesAnnotation.Controls["tbNameRu"].Text = _normDoc.AddInfoRu ?? string.Empty;
   }
</code></pre>

<p>I think that if <code>_normDoc.AddInfoRu == null</code> then <code>ucRusKazTextBoxesAnnotation.Controls["tbNameRu"].Text</code> will be equal empty string.<br>
  But I am got  error: <code>NullReferenceException</code>.
Can you explain me why?</p>

<p>PS. ucRusKazTextBoxesAnnotation not equal null;</p>

<p><strong>EDIT</strong>: Sorry,  I find error, yes, tbNameRu not found, because they are inside Panel control.</p>
