title: Why updating existing tables by Entity Framework Tool ALWAYS cause errors?
body: <p>Adding new tables by <strong>right click on mouse in diagram -> Update Model from Database</strong> succeeds.</p>
  
  <p>BUT, updating existing tables fails. I recieve this error:</p>
  
  <pre><code>Error 5: The element 'Principal' in namespace 'http://schemas.microsoft.com/ado/2008/09/edm' has incomplete content. List of possible elements expected: 'PropertyRef' in namespace 'http://schemas.microsoft.com/ado/2008/09/edm'.
  </code></pre>
  
  <p>To updated existing tables I do:</p>
  
  <ol>
  <li>delete them from edmx</li>
  <li><strong>right click on mouse -> Update Model from Database</strong> and checking those tables</li>
  </ol>