Pass a byte array pointer from c# to COM developed in c++

Hi,

I have a problem in a project. I need pass trough pointer a byte array, byte[], into a COM(cpp) and the same pointer give me back a file byte array.
I have tried pass the pointer, but unsuccessfully.
in cpp: DWORD giveSomething(BYTE* Resp), where "Resp" giv me back a file byte array.

Someone know what I can do for solve my problem? Use a byte[] pointer from c# to cpp.

regards

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