title: Problem referencing directshow filter from C#
body: <p>I have a custom DirectShow filter created by extending the ezrgb24 filter from the DirectShow sample documentation. </p>
  
  <p>I am using this filter (indirectly) in C# through a 3rd party multimedia SDK (LeadTools). Now I need to add a reference to the filter's DLL to the project so that I can cast an IUnknown interface retrieved by the SDK to the filter's own custom interface.</p>
  
  <p>I have tried adding the DLL reference through add reference -> browse, and by using tlbimp directly at the commandline. Both approaches result in the error 'C:\windows\system32\ezrgb24.dll' is not a valid type library.</p>
  
  <p>Am I missing something? The extensions I have made to the ezrgb24 example are pretty trivial structurally, essentially if anyone has the DirectShow examples they know exactly the code I am working with.</p>
  
  <p>Any and all help is greatly appreciated.</p>
  
  <p>Tony.</p>