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  1. #1
    Join Date
    Sep 2010

    Calling C++ DLL from VB

    I'm not sure whether this is a VB forum question or a C++ question, but I'll try here first.

    I have an API library written in C++ (including source) which compiles to several DLLs. I want to call the functions in the library from VB but I can't get the parameter passing right.

    Simple ones like:
    void yasdiMasterInitialize( char * cIniFileName, DWORD * pDriverCount)

    Can be called by:
    <DllImport("yasdimaster.dll", CallingConvention:=CallingConvention.Cdecl)> Public Function yasdiMasterInitialize(ByVal IniFile As String, ByRef DriverCount As UInt32) As Integer
    End Function

    But anything with arrays:
    int GetDeviceName( DWORD DevHandle, char * DestBuffer, int len)

    I can't seem to get right:
    <DllImport("yasdimaster.dll", CallingConvention:=CallingConvention.Cdecl)> Public Function GetDeviceName(ByVal DeviceNumber As UInt32, ByVal DeviceName As String, ByVal Length As Integer) As Integer
    End Function

    The above example runs but returns nothing. If I change DeviceName to ByRef, I get protected memory errors.

    The full library and documentation is available on the internet if anyone would like to download it and I've successfully compiled it with VS2010.

  2. #2
    Join Date
    Jan 2006
    Fox Lake, IL

    Re: Calling C++ DLL from VB

    C++ has POINTERS. VB.Net doesn't, so, there is a MAJOR problem...

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  3. #3
    Join Date
    Apr 2004
    England, Europe

    Re: Calling C++ DLL from VB

    In .net we use a string builder class as input when calling such a C function and the system automatically takes care of things. If that is not possible, is there any way of passing in a raw array from VB?
    Last edited by Zaccheus; September 2nd, 2010 at 04:54 AM.
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