无法在DLL中找到入口点

Question

I have a C# application from which I am trying to send a parameter to a C++ function. However, I am getting the error (mentioned in the subject)

C# application:

static class SegmentationFunctions
{
[DllImport("MyApplication.dll", EntryPoint = "fnmain", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        public static extern int fnmain(string search);
    }
}

public partial class MainWindow:Window
{
public MainWindow()
{
InitializeComponent();

string search = "test string here";
int scommand = SegmentationFunctions.fnmain(search);
}

C++ file.h

extern "C" QUERYSEGMENTATION_API int fnmain(char query[MAX_Q_LEN]);

C++ file .cpp

extern "C" QUERYSEGMENTATION_API int fnmain(char searchc[MAX_LEN_Q])
{

do something...

}

Answer 1

Dependency Walker can show you what functions are effectively exported from the DLL. You will be able to see if your fnmain is there at all, or it is _fnmain instead , or has a C++ decoration in its name.

Answer 2

Note that by default visual studio will not copy your native output to the same folder as your managed output.

manually copy native output to your managed build folder and try again - if that is your problem then you need to change the C++ build settings to put the destination folder the same as your managed app folder.

Your code is correct - so long as the QUERYSEGMENTATION_API macro is defined correctly and your dll is in fact built as "MyApplication.dll"

I would manually run the executable from the file system - making sure that the latest exe and dll are in the same folder, and if it fails run depends.exe to figure it out.