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Hi,
I have a DLL function as the following, when I pass the parameter byRef, it does work fine instead I need to pass it byVal, why?

int _stdcall mfunction(int a,char * b);
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As my fourth grade teacher used to say, "That's just the way it is!!!"

Only kidding... kinda. API calls written in, say, C, actually expect a different sort of "string" data than the VB "string" (and so on for many other data types). If you send the value, it works fine, because it converts the value. If you send the pointer of the actual variable, it will look at the variable, and say "what the heck is this?" At which point, quite likely, you get a GPF or a page fault.....

So, the workaround is.... use ByVal. It's the VB method for passign values to an external DLL API.