Hook into a unknown function in a dll using C#

Question

Is it possible to find out what functions are available in an arbitrary dll file and then call these functions using C# interop services.

Answer 1

You can analyze the exported functions of any native module (DLL or EXE) using tools such as dumpbin. Once you have the signatures of the exported functions, you can write P/Invoke wrappers for any of them you wish.

Alternatively, you can use a tool like the P/Invoke Interop Assistant to automagically do the grunt work for you.

However, all of that relies upon the native module having listed the functions you're trying to call in its export table. If what you're looking to hook into is not actually exported, then you will have to resort to old-fashioned spelunking with GetProcAddress, etc.

Answer 2

If the .dll is a managed assembly, then you can use the classes in System.Reflection to find and run arbitrary methods.

If it's a native Win32 dll, then you have a much harder road to hoe: you have to P/Invoke the Win32 APIs LoadLibrary and GetProcAddress and call the functions you want through an unsafe pointer.