title: TFS get user by name
body: <p>I'm trying to add a test run by the TFS API from excel.<br>
  In one of the field in the excel I got the user who executed  the tests.<br>
  I want to update it in the server in order to update it I need to get the user as <code>TeamFoundationIdentity</code></p>
  
  <pre><code>ims = _tfs.GetService&lt;IIdentityManagementService&gt;();
  TeamFoundationIdentity UserID = ims.ReadIdentity(IdentitySearchFactor.DisplayName,  
    userName, ReadIdentityOptions.None);
  </code></pre>
  
  <p>Please help me to fix it.</p>