[HELP ME]Use of Dll "CFReader.dll"

Hi at all.
I'm an italian developper, a young developper..
I'm doing an application in c# for pocketpc.
I'v this dll and an example of use in c++ (.h and .cpp)
In the .h file there are this code:
typedef long (CALLBACK* LP_GETDLLVERSION)(void);
LP_GETDLLVERSION GetDLLVersion;
And in the .cpp:
GetDLLVersion =
(LP_GETDLLVERSION)GetProcAddress((HMODULE)readerdll,_T("GetDLLVersion"));

I've translate this code in:
[DllImport("CFReader.dll",CharSet=CharSet.Auto,EntryPoint="GetDllVersion")]
private static extern Int32 GetDllVersion();
And i call:
GetDllersion();
The program compile but it lunch a MissingMethodException.I've put the
dll on the app directory but it doesn't work.
What can i do?

Thanks
giomax