title: GAC – Assembly is in the GAC but “Could not load file or assembly”
body: <p>I have an Interop dll that was generated by Visual Studio for a third-party COM object that I am consuming in a .NET dll.</p>
  
  <p>I have registered both my consuming dll and the Interop dll in the GAC.  I have to use the GAC because these DLLs are being used by a SharePoint 2010 workflow.</p>
  
  <p>When the execution gets to the point where my dll calls the Interop dll the following error was thrown”   “Could not load file or assembly” … “The system could not find the file specified” together with the expected version and public key.</p>
  
  <p>If I examine the Fusion Assembly Binding Log Viewer, the following error is listed in the log entry of the Interop dll: </p>
  
  <pre><code>LOG: GAC Lookup was unsuccessful.
  </code></pre>
  
  <p>I can see that assembly in the GAC, and it has the correct version and public key token as specified in the FileNotFound exception.</p>
  
  <p>What’s going on?</p>