title: Rotate image (byte array) in datatable
body: <p>I have a datatable set as itemsource for a datagrid (datagrid showing several columns of the datatable).  All columns except one have text, the last column holds an image as a byte array.
  The picture-column is bound to an image control, which shows the image from the selected line in the datagrid.
  The images the datatable holds can be collected from a disk-location or a database.  Eventually, they will all be saved in the database.</p>
  
  <p>I have a button, which <em>should</em> rotate the shown image 90° clockwise, and save it again (as byte array) in the datatable on the exact same row (and column).</p>
  
  <p>I tried about a kazillion ways to do this, but no luck whatsoever.
  Can someone please help me rotating and saving this picture?</p>