C# communicate with unmanaged C DLL from C#

[MichK]

Hi everyone,

I'd like to implement some external (in C-written) DLL-functions to my C# software.
I'm having some problems with the declaration though, since I'd like to pass an array (which will be numerically changed from within the dll-function).
The IDE keeps telling me I'm about to change some memory. The exact message is:

"AccessViolationException was unhandled
Attempted to read or write protected memory. This is often an indication that other memory is corrupt."

Below is a piece of code as far as I've got it now:

At the c# side:
 
    class DSPToolBox
    {
 
        // Externe DSP dll
 
        unsafe public static extern double S_MakeMOVRMS(short* arrIn, double* arrR, long Size,
            short Order, double* arrA, double* arrB, double CaliOffset);
 
}
 
class someother class
{
long ret;
 
double[] A = ACoeff.A;
double[] B = ACoeff.B;
double[] R = ACoeff.Register;
short* Temp = StartPtr;
 
fixed (double* pACoeffA = A) 
fixed (double* pACoeffB = B)
fixed (double* pACoeffR = R)
 
ret = DSPToolBox.S_MakeMOVRMS(Temp, pACoeffR,
                    (long)DiskBuffer.Length, Order, pACoeffA, pACoeffB, 0);
 
}
//--------------------------------------------------------------------------------------------------------
At the dll (c) side:
 
double _stdcall __declspec(dllexport) S_MakeMOVRMS
( short* arrIn, double* arrR, long Size, short Order, double* arrA, double* arrB,
  double CaliOffset)
{
 arrR[0] = 5*2;
 
blabla....
 
 return 0;
}
 
 

Calling this dll was not a problem at all in VB6, I simply used byref to pass the arrays (with element 0), and it worked, so the dll is ok. Passing the pointers doesn't seem that simple in c# as in VB though (how ironic that may be).
Does anybody maby know how one could handle this?

Thanks.
-Michiel