hmm.. i'm not a c++ guru, but i once wrote a little c++ demo lib that was callable from c# and i'm not sure if this is important, and if you can do anything about it but: 1) in my method-declaration i used the stdCall keyword: void __stdcall foo(unsigned int *param1, unsigned char *param2, unsigned char *param3, void *Handle) --> i think the default calling convention for pInvoked Method is stdCall so if it's not declared that way it might fail.. 2) in the exports.def of the library i had to put this in order to make it work: EXPORTS foo @1 --> if this is missing, it might explain the EntrypointNotFound - exception greets m@u