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VB and pointers et al

Posted on 2003-11-06
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Last Modified: 2010-07-27
This is something that's probably been covered time and time again.  I'm working with external DLLs that require pointers to byte array and also pointers to the equivalent of a DWORD.

I think I understand the pointer to a byte array, using the concept of ByRef and myArray(0) to pass to a DLL or return from a DLL, but what about a DWORD, how can I pass a pointer to my variable in VB and either pass my number to the DLL or get it to pass a response back into my variable?

If that makes any sense, I'll be very surprised.

Thanks
Simon
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Question by:sbennetts
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7 Comments
 
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AlexFM earned 500 total points
ID: 9693665
If C++ function has DWORD parameter, use ByValue Integer in VB.
If C++ function has DWORD* parameter, use ByRef Integer in VB.
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by:sbennetts
ID: 9693842
Is there a definitive list for this kind of thing?  It's something I always spend ages and ages on...
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Expert Comment

by:AlexFM
ID: 9693985
I usually find some API with parameters of required type and see how API viewer generated API declaration. For example, to see difference between DWORD and DWORD* you can compare GetComputerName and GetWindowText.
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Author Comment

by:sbennetts
ID: 9694091
...but how does that tell you about the actual function call in the DLLs?
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Author Comment

by:sbennetts
ID: 9694133
i.e. what they are expecting in...
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Expert Comment

by:AlexFM
ID: 9694384
Compare GetComputerName and GetWindowText API declarations in MSDN and generate their VB declarations using API Viewer. When Dll function has DWORD* parameter, you pass ByRef Integer. Dll gets DWORD* and may change this variable.
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Author Comment

by:sbennetts
ID: 9701362
Many thanks
Simon
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