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?

could you try using `SafeArray`? – Daniel A. White Jul 02 '14 at 18:52 — Daniel A. White, Jul 02 '14 at 18:52

score 8 · Accepted Answer · answered Jul 02 '14 at 19:04

8

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?

answered Jul 02 '14 at 19:04

Eugene Podskal

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The mono interop docs say that structs are layout sequential by default, which is why I think I should be fine.http://www.mono-project.com/Interop_with_Native_Libraries – SaldaVonSchwartz Jul 02 '14 at 19:10
Ok, understood. So have you tried to marshal it ByVal? – Eugene Podskal Jul 02 '14 at 19:11

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

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