调用我能从托管代码中思考的最基本的c ++函数的AccessViolationException

I'm trying to learn how to use managed/unmanaged code interop, but I've hit a wall that 4 hours of googling wasn't able to get over. I put together 2 projects in visual studio, one creating a win32 exe, and one creating a windows forms .NET application. After a bunch of mucking around I got the C# code to call into the c++ code correctly, but from here I started getting AccessViolationException everytime I got in there. Here is the code from the .cpp file:I'm trying to learn how to use managed/unmanage