Question

I’m working on a fairly convoluted project in which I’m accessing classes written in plain-old-C++ from a project using C++/CLI. It’s a Windows Forms GUI project that uses a lot of the same functions as its (non-CLI) C++ sister project.

In one of my classes that I’m trying to adjustment to work in both environments, I’m polling keypresses with this function:

inline bool IsKeyDown(unsigned char ch) const { 
    return (GetAsyncKeyState(ch) & (1u << 15)) != 0; 
}

I’m getting both Unresolved Token and Unresolved External Symbol errors on
"extern "C" short __stdcall GetAsyncKeyState(int)" (?GetAsyncKeyState@@$$J14YGFH@Z) referenced in function "public: bool __clrcall Engine::InputManager::IsKeyDown(unsigned char)const " (?IsKeyDown@InputManager@Engine@@$$FQBM_NE@Z)

Obviously, the issue is related to GetAsyncKeyState() but I’m not sure what needs to be different for a CLI-friendly implementation. Can anyone direct me how to fix this? The function works properly in my non-CLI environment (and has for months). I’m very new to this CLI stuff so any help would be wonderful and no help could be too-specific.

If it helps, I’m using Visual Studio 2010 and compiling with the /clr parameter (not :pure or :safe).

Answer 1

The MSDN library provides the details of which header files and libraries need to be included for any particular function.

In this case, you need windows.h (which you must already have) and user32.lib (which is probably missing). So add

#pragma comment(lib, "user32.lib")

at the top of your code and all should be well. Alternatively, you could add user32.lib to the list of libraries in the project properties pages, remembering to do this for each configuration, e.g., debug as well as release.