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Asked: 2026-05-26T00:35:59+00:00

I’m trying to call a C++-compiled DLL from VB.net and I’m running into some

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I’m trying to call a C++-compiled DLL from VB.net and I’m running into some problems. Seems like there’s an obvious solution, but I can’t figure it out.

Here is the function declaration in C++:

 MyFunction(int trailingaveragesize, double sigmasize, int myflag, int sizeSeries, double *Xdata, double *Ydata, int sizeinputparameter, int *averagePairs, double *PositionsSize, double *PnLSize)

Here is how I’m calling it in VB.Net:

 Call MyFunction(200, 1, 1, 230, a_PriceSeries(0), a_PriceSeries(0), 1, a_Averages(0), a_PositionSeries(0), a_PnLs(0))

The maximum size of the input matrices are defined by sizeSeries (230), and the size of all my input matrices are 10000 (just so I won’t accidentally overflow), yet still i’m getting an unhandled AccessViolationException error

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

My question is – If I’m not exceeding the bounds of my matrices, what other reasons would throw this error? Is it because I’m only passing the first entry in my matrices ByReference then it’s trying to access other elements of that matrix? If so, how would I fix that?

EDIT:

Here’s how I’m declaring it in VB

 Declare Function MyFunction Lib "C:\Dev\asdf.dll" (ByVal trailingaveragesize As Long, ByVal sigmasize As Double, ByVal myflag As Long, ByVal sizeSeries As Long, ByRef Xdata As Double, ByRef Ydata As Double, ByVal sizeinputparameter As Long, ByRef averagePairs As Long, ByRef PositionsSize As Double, ByRef PnLSize As Double) As Double
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1 Answer

  1. Editorial Team
    Declare Function MyFunction Lib "C:\Dev\asdf.dll" (ByVal trailingaveragesize As Long, _
  ByVal sigmasize As Double, ByVal myflag As Long, ByVal sizeSeries As Long, 
  ByRef Xdata As Double, ByRef Ydata As Double, ByVal sizeinputparameter As Long, 
  ByRef averagePairs As Long, ByRef PositionsSize As Double, ByRef PnLSize As Double) As Double

    The declaration is simply wrong, this resembles a vb6 declaration. An int in C code is an Integer in vb.net, not a Long. The Xdata and Ydata are highly likely to be arrays, not a byref double. Declare them as ByVal Double(). The other byref args are harder to guess.

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