title: synchronize expand/collapse datagridrowgroupheaders between silverlight datagrid
body: <p>Two datagrids side by side.  One is the summary of the other.  They are both grouped the same.  So if I scroll one, the other scrolls.  The scrolling synchronization works fine (although not  trivial), but I'd like to sync expand/collapse of the groups.  </p>
  
  <p>The only way I found was to use Loading row group and loading row events.  I got it working to some point until I realized that scrolling made all this not working.</p>
  
  <p>I wanted to prevent expand/collapse.  We do this by disabling the group header.  But... I have controls inside the headers, now I can not interact with my controls.</p>
  
  <p>So I can not sync expand/collapse, and I can not disable it.</p>
  
  <p>Any suggestions?</p>