title: UI Automation: Open File dialog elements tree contains not all elements
body: <p>I'm trying to use UI Automation with C# to type file path in opened <code>Open</code> dialog and then press Open button. I'm able to find the dialog itself, but searching for inner elements (file path text box and Open button) gives no result. When I traverse elements tree writing elements to log file, I see that the log is obviously too short and not all elements printed out.</p>
  
  <p>Strange behavior: if I switch with mouse on another window, traversing of the dialog returns all elements and I'm able to find desired controls and interact with them.</p>
  
  <p>I've tried many approaches to bypass the problem:</p>
  
  <ul>
  <li>open some window, switch to it with <code>AutomationElement.SetFocus</code>;</li>
  <li>search for element with Win API (<code>FindWindowEx</code>);</li>
  <li>get <code>AutomationElement</code> by point on screen within dialog's bounding rectangle iterating by <em>x</em> and <em>y</em> with some step.</li>
  </ul>
  
  <p>No one approach give me desired result.</p>
  
  <p>What can cause incomplete elements tree using UI Automation and what is workaround for this?</p>
  
  <p>My scenario is:</p>
  
  <ol>
  <li>test clicks on a button on web page</li>
  <li>standard Windows dialog to select a file is opened</li>
  <li>I'm trying to fill file path text box and press Open button using UI Automation</li>
  </ol>