Marshalling array of structures from c++ to c# in WinCE

Question

I'm trying to Marshal the following structures from c++ to c# on a Windows CE program and compact framework 2.0. I'm having a lot of difficulties with the marshalling of strings.

I have this c++ code:

#define Console_Parameters_MAX 50

struct AllParameters {
  Parameter Parameters[Console_Parameters_MAX];
} ;

struct Parameter { 
  int Index;
  int Id; 
  char Value[20];
};

extern "C" {
   BOOL GetAllConsoleParameters(AllParameters *pItem);
}

and this are the corresponding c# code:

[StructLayout(LayoutKind.Sequential)]
public struct AllParameters {
  [MarshalAs(UnmanagedType.ByValArray, SizeConst = 50)]
  public Parameter[] Parameters
}

[StructLayout(LayoutKind.Sequential)]
public struct Parameter {
  public int Index;
  public int Id;
  [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]
  public byte[] Value;
}

[DllImport("exemple.dll", SetLastError = true)]
public static extern bool GetAllConsoleParameters([MarshalAs(UnmanagedType.Struct)] ref AllParameters pItem);

and this is how I invoke it:

AllParameters item = new AllParameters();
if (AppAPI.GetAllConsoleParameters(ref item)) {
   var array = item.Parameters;
}

When I call the GetAllConsoleParameters I get exception NotSupportedException. I've tried many configurations but with no success.

Can anyone advise on how to achieve it?

Thanks in advance

Answer 1

following my solution, c++ code:

/* - not used
#define Console_Parameters_MAX 50

struct AllParameters {
  Parameter Parameters[Console_Parameters_MAX];
} ;
*/

struct Parameter { 
  int Index;
  int Id; 
  char Value[20];
};

extern "C" {
   BOOL GetAllConsoleParameters(Parameter pItem[], int size);
}

and corresponding c# code:

/* - not used
[StructLayout(LayoutKind.Sequential)]
public struct AllParameters {
  [MarshalAs(UnmanagedType.ByValArray, SizeConst = 50)]
  public Parameter[] Parameters
}
*/

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct Parameter {
  public int Index;
  public int Id;
  [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
  public byte[] Value;
}

[DllImport("exemple.dll", SetLastError = true, CharSet = CharSet.Unicode)]
public static extern bool GetAllConsoleParameters([MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1), Out] ConsoleParameter[] myStruct, int size);

and code invoke:

ConsoleParameter[] item = new ConsoleParameter[50];
if (AppAPI.GetAllConsoleParameters(item, 50)) {
   var array = item;
}

thanks a lot for help