title: TfsConfigurationServer.GetService<VersionControlServer>() always returns null
body: <p>I'm trying to connect to TFS 2010 using TFS SDK, but can't get VersionControlServer service.</p>
  
  <pre><code>var servers = RegisteredTfsConnections.GetConfigurationServers(); // ok
  </code></pre>
  
  <p>then</p>
  
  <pre><code>var tfs = new TfsConfigurationServer(servers.First().Uri, CredentialCache.DefaultNetworkCredentials);
  // or
  var tfs = new TfsConfigurationServer(servers.First());
  </code></pre>
  
  <p>both always returns null:</p>
  
  <pre><code>var vc = (VersionControlServer)tfs.GetService&lt;VersionControlServer&gt;(); // null!
  </code></pre>
  
  <p>What should I do?</p>