Marshaling C++ struct with fixed size array into C#

Question

I have a C# struct declared like so:

public struct AdvertisementData {
    public byte SomeId;
    [MarshalAs(UnmanagedType.LPArray , SizeConst = 12)]
    public byte[] AnArray;
  }

And it's C++ counterpart:

struct AdvertisementData {
  uint8_t SomeId;
  uint8_t AnArray[12];
};

When I try to send a reference to a stack-allocated instance of the above struct from C++ to C#, I get: "Structure field of type Byte[] can't be marshalled as LPArray." Any idea what I'm doing wrong?

Limbourg

could you try using SafeArray? – Trice

Answer 1

Try to marshal it as ByValArray:

 [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
  public byte[] AnArray;

And also, are you sure that you do not need to set any LayoutKind for your struct?

Harmonics

The mono interop docs say that structs are layout sequential by default, which is why I think I should be fine.mono-project.com/Interop_with_Native_Libraries – Limbourg

Ok, understood. So have you tried to marshal it ByVal? – Harmonics