Return a struct with struct field from c++ to c# pinvoke

Question

I'm trying to return from my native c++ code to c# code a struct with field of other struct but have an error : Method's type signature is not PInvoke compatible.

this is my c++ code:

namespace path
{
struct Vector3
{
public:
    float x;
    float y;
    float z;
};

struct PointState
{
public:
    Vector3 position_;
    bool reformation;
};

}

Here my api functions:

extern "C"
{
PATHFINDER_API void SetupGraph(const char * json);
PATHFINDER_API path::Vector3 CheckReturn();
PATHFINDER_API path::PointState CheckStruct();
}

And this is my C# struct code:

 [StructLayout(LayoutKind.Sequential)]
public struct Vector3
{
    public float x;
    public float y;
    public float z;
};

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct PointState
{
    [MarshalAs(UnmanagedType.LPStruct)]
    public Vector3 position_;
    public bool reformation;
};

and Pinvoke DLLImport:

        [DllImport("path", CallingConvention = CallingConvention.Cdecl, ExactSpelling = false, EntryPoint = "CheckStruct")]
    private static extern PointState CheckStruct();

    public PointState CheckReturn2()
    {
        return CheckStruct();
    }

Pls, what i'm doing wrong? I can't find answer by myself.

Your code is not complete. We can't see the C++ code that declares PointState. — David Heffernan
– David Heffernan, Commented Feb 26, 2018 at 11:21

David Heffernan · Accepted Answer · 2018-02-26 11:58:54Z

2

There are a few problems with your code:

You used [MarshalAs(UnmanagedType.LPStruct)] on the nested struct, but that's just wrong. That field isn't a pointer. That attribute should be removed.
The bool type can't be marshalled in a return value. You can replace the C# bool with byte to resolve that, and then compare the value against zero.
In addition, some of the attributes that you have added seem needless. I suspect that you did the usual thing of trying lots of changes at random, but then leaving them in the code that you posted here.

I'd use the following declarations:

[StructLayout(LayoutKind.Sequential)]
public struct Vector3
{
    public float x;
    public float y;
    public float z;
};

[StructLayout(LayoutKind.Sequential)]
public struct PointState
{
    public Vector3 position_;
    private byte _reformation;
    public bool reformation { get { return _reformation != 0; } }
};

[DllImport("path", CallingConvention = CallingConvention.Cdecl)]
private static extern PointState CheckStruct();

answered Feb 26, 2018 at 11:58

David Heffernan

616k46 gold badges1.1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Dmitry Abramenkov Over a year ago

Omg, thanks a lot! I was think that problem is in struct, and problem was in bool. Yes, you absolutely right, i try all i can, and not clean up.

Collectives™ on Stack Overflow

Return a struct with struct field from c++ to c# pinvoke

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related