title: microsoft.visualstudio.diagnostics.servicemodelsink.dll -- present on most systems, missing on new system
body: <ul>
  <li>ASP.NET app, </li>
  <li>Win2012-R2</li>
  <li>.NET 4.6.1 installed</li>
  </ul>
  
  <p>We are setting up our app on a new IIS / Win2012-R2 server, and our app throws this error:</p>
  
  <pre><code>The type 'Microsoft.VisualStudio.Diagnostics.ServiceModelSink.Behavior, Microsoft.VisualStudio.Diagnostics.ServiceModelSink, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' registered for extension 'Microsoft.VisualStudio.Diagnostics.ServiceModelSink.Behavior' could not be loaded. (C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config line 241)
  </code></pre>
  
  <p>We see that this dll:</p>
  
  <p><code>microsoft.visualstudio.diagnostics.servicemodelsink.dll</code> is missing. It is present on our other servers.</p>
  
  <p>Where does it come from? (it is in the GAC magically on our existing Win2012R2 servers)</p>
  
  <p>We have carefully reviewed the pieces of Windows installed, and are confident all the Windows pieces present on the old servers are also on the new server.</p>