COM to .NET Interoperability

If you want to use a COM type in your C# code, the process is straight forward, right? You just need to use the type library importer and that's fine, but what if you don't have one and you can't take a look at the IDL file? You just have the COM DLL server.

As an example, try using the IActiveDesktop interface.

What's the approch used to solve this kind of problem?