Call C++ dll from C# dll and get nothing

Question

I am developing a C# dll for Revit(a software for Civil Engineering), and the C# dll calls the function from unmanaged C++ dll that was developed by myself. When the function compareMarkedPointsWithBIMModel_ in the unmanaged C++ dll is called, nothing is got, it seems that the function in the unmanaged C++ dll does not execute.

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Here are the details:

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in the unmanaged C++ dll

extern "C" __declspec(dllexport) void compareMarkedPointsWithBIMModel_(
char* a_,
const double* list,
int listLength) {

std::vector<std::vector<double>> b; 
for (int i = 0; i < listLength / 6; i++)
{
    std::vector<double> cc;
    for (int j = 0; j < 6; j++)
    {
        cc.push_back(list[i * 6 + j]);
    }
    b.push_back(cc);
}

std::string a = a_; 

CompareMarkedPointsWithBIMModel cmpb(a, b);
cmpb.readMarkedPoint3DInfo();
cmpb.computeAB();
cmpb.computeRT();
cmpb.computeDeviation();
system("pause");

}

in the C# dll

[DllImport("Test_OpenCV.dll")]
    public static extern void compareMarkedPointsWithBIMModel_(
        string st1,             
        ref double list_,     
        int listLength_);       

    public Result Execute(
        ExternalCommandData commandData,
        ref string messages,
        ElementSet elements)
    {                       
        string smallImagesPath =        
            "C:/D/Bundler04ForReconstruction/results/result_DF510";            
        double[] list;
        int listLength;
        setList1(out list, out listLength);           

        compareMarkedPointsWithBIMModel_(
            smallImagesPath,
            ref list[0],
            listLength);

        return Result.Succeeded;
    }        

    public void setList1(out double[] list, out int listLength)
    {
        /// realize of the function         

    }

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I have searched the Internet for solutions, but got no useful solutions. I have also tried to call the unmanaged C++ dll (especially the function) in a C# console project, and it works! It is strange. Also, the platforms for the unmanaged C++ dll and C# dll are all x64. So, why the function not execute, is there anything wrong? Thank you in advance.

Answer 1

Do you get an exception? Is the unmanaged DLL using COM? If so, call it in a MTA thread (just run it in a background task), since it's working in a console application, this might be the problem.