title: Add my UserControl to DevExpress ASPxGridView column header
body: <p>I have an ASPxGridView on my page which has a few columns of data.  Basically what I want to do is to add a tooltip (which I have as a user control) to each of the column headers.  I don't think that it is possible to do this in the markup as I don't want to loose any of the functionality already in the grid headers (e.g. filter, etc) so what I need to do is loop through the header cells somehow to add the control in dynamically.</p>
  
  <p>I have tried using the <code>OnHtmlRowPrepared</code> event but this does not fire for headers!</p>
  
  <p>I want to achieve something like the following so the tooltip will show on hover (the tooltip is already implemented).</p>
  
  <p><img src="https://i.stack.imgur.com/65LTf.png" alt="enter image description here"></p>
  
  <p>Any ideas?</p>