I added MyAssembly.dll as an additional reference to my query, and that works fine: I am able to use various classes from it with no trouble.
One of the methods for one of the classes in MyAssembly.dll references another dll (Wrapper.dll). Wrapper.dll uses [DllImport] to access functionality in a C++ dll (C.dll):
[DllImport("C.dll", CallingConvention = CallingConvention.StdCall, EntryPoint ="CPlusPlusFunction")] internal static extern UInt32 _CPlusPlusFunction([MarshalAs(UnmanagedType.LPWStr)] string file_path);
While this method works perfectly fine when executed from MyApp.exe that references MyAssembly.dll (which references Wrapper.dll, which references C.dll), in LINQPad I can't get it to work.
If I only add a reference for MyAssembly.dll and attempt to run the method, I get:
DllNotFoundException: Unable to load DLL 'C.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
If I add an Additional Reference for just Wrapper.dll, I get the same error.
If I add an Additional Reference for both Wrapper.dll AND C.dll, I get:
Metadata file 'C.dll' could not be opened -- 'An attempt was made to load a program with an incorrect format.'
If I add an Additional Reference for just C.dll I get the same error.
Any idea on how I can get this to work in LINQPad like it does in MyApp.exe?
You do it the exact same way, you'll have to copy it in the same directory as the EXE so Windows can find it. The LINQPad EXE in this case. C:\Program Files (x86)\LINQPad4 by default. Or any directory that's on the PATH, c:\windows\syswow64 is the infamous choice. Best not to do that.