Mono(Unity) PInvoke struct with wchar_t[]

[kombain32]

I'm trying to PInvoke (on Windows) a method which has a struct parameter with wchar_t[].

The C++ (Qt) declaration looks this:
`
#define MAX_FIELD_LEN (30)

typedef void* Context;
typedef void* Handle;

struct Info
{
wchar_t id[MAX_FIELD_LEN];
wchar_t version[MAX_FIELD_LEN];
wchar_t date[MAX_FIELD_LEN];
uint8_t channels;
wchar_t serialNumber[MAX_FIELD_LEN];
uint32_t speed;
};

#define LIB_EXPORT __stdcall

LIB_EXPORT
Status Open(Context ctx
, Type type
, qsizetype idx
, Info& Info
, Handle &handle
);

enum Status
{
/Statuses/
}

enum Type
{
/Types/
};

`

The C# declaration looks this:

`
[StructLayout(LayoutKind.Sequential)]
public struct Info
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 30)]
public char[] id;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 30)]
public char[] version;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 30)]
public char[] date;
public byte channels;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 30)]
public char[] serialNumber;
public uint speed;
}

[DllImport("lib", CallingConvention = CallingConvention.StdCall)]
public static extern Status Open(IntPtr context, Type type, int index, ref Info data, ref IntPtr handle);

`
This works in WinForms, but in Mono (Unity), the struct is not filled with values. I suspect that it's about different string marshalling in Mono and MS, but I can't figure out how to fix it.