在C＃中使用struct作为返回值调用C函数

Question

I simply want to call a C function from a DLL in C#. This C function returns a struct.

Here the .h-file declaration of the c dll:

typedef struct t_Point{
 int x;
 int y;
} Point;


Point myFuncs();

Now I want to use this function in C#. Wrapper.cs:

using System.Text;
using System.Runtime.InteropServices;

namespace CSharp_mit_OpenCV
{
    [StructLayout(LayoutKind.Sequential)]
    public struct Point
    {
        public int x;
        public int y;
    };

    class Wrapper
    {
        [DllImport("OpenCV Test.dll", CharSet= CharSet.Auto)]
        [return: MarshalAs(UnmanagedType.Struct)]
        public static extern Point myFuncs();
    }
}

The usage is as follows:

Point p = Wrapper.myFuncs();

(Naming is probably not the best)

myFuncs only declares a struct, puts some values to x and y and returns it. The problem: The values I get in C# are different than those generated in the C function. It should be 4 and 2 and it is 0 and 111226272. What's the problem here?

Thanks for any help!

Answer 1

Your marshall code seems correct, what is the pack layout of the unmanaged method? LayoutKind.Sequential will treat your ints as 4 byte. Check if this is correct.