Good day,

Perhaps this should be on the Interop newsgroup. Sorry if it should.

I'm trying to PInvoke a function in a native DLL via its ordinal number.
The native C++ function, ordinal number 1, has the declaration:

int __cdecl CalcAverage(int,int,int);

My C# declaration for that function is:

[DllImport("pinvoke_tests.dll", EntryPoint = "#1", CallingConvention =
CallingConvention.Cdecl)]
public static extern int CalcAverage(int first, int second, int third);

When I run the code I get a NullRef exception at the following line of code:

Assert(NativeFunctionWrapper.CalcAverage(-400, -500, -600) == -500);

In inspecting the first few lines of the disassembly for the above
code-line I see:

push        0FFFFFDA8h
mov         edx,0FFFFFE0Ch
mov         ecx,0FFFFFE70h
call        dword ptr ds:[00905510h]

Either I misunderstand the "C" calling convention, or the JIT has missed
 my request to use it.

I understand the "C" calling convention to mean:

- args are pushed right to left
- caller must free args

and most importantly,

- all inbound args passed on the stack, none in registers

Any thoughts? If I'm not wrong about the calling convention, how do I
persuade the JIT to use it?

Thanks

Mike