How do I copy an array of integers between two Delphi Prism applications using WM_COPYDATA?

Question

I'm trying to use WM_COPYDATA to copy data between two Delphi Prism applications on the same computer.

In the sender application I have the code:

type
  [StructLayout(LayoutKind.Sequential)]
  CopyDataStruct = public record
    var dwData: IntPtr;
    var cbData: System.Int32;
    var [MarshalAs(UnmanagedType.ByValArray, SizeConst := 11)]
    lpData: array[0..10] of Int32;
  end;


  ConsoleApp = class
  public
    const WM_COPYDATA: System.Int32 = $4a;//WM_COPYDATA  0x004A
    class method Main;
    [DllImport('user32.dll', EntryPoint := 'FindWindow')]
    class method FindWindow(lpClasName: System.String; lpWindowName: System.String): System.IntPtr; external;
    [DllImport('user32.dll', EntryPoint := 'SendMessage')]
    class method SendMessage(hWnd: System.IntPtr; Msg: System.Int32; wParam: System.Int32; var lParam: CopyDataStruct): System.Int32; external;
  end;


implementation


class method ConsoleApp.Main;
var
  cd   : CopyDataStruct;
  WHnd : IntPtr;
  i : word;
  MyArray : Array[0..10] of Int32;
begin
  cd.dwData := IntPtr(0);
  for i := 0 to 10 do
    MyArray[i] := i;
  cd.lpData := MyArray;
  cd.cbData := MyArray.Length;
  WHnd := FindWindow(nil, 'PrismForm');
  if (WHnd<>System.IntPtr.Zero) then
  begin
    SendMessage(WHnd, WM_COPYDATA, 0, var cd);
    Console.WriteLine('Message sent');
  end
  else
    Console.WriteLine('Window not found');
 Console.ReadKey();
end;

In the receiver app I have the same CopyDataStruct definition and the code:

method PrismForm.WndProc(var m: Message);
var
  cd : CopyDataStruct;
  s : System.String;
  i : Int32;
begin
  case m.Msg of 
    WM_COPYDATA : begin
                    TextBox1.Text := "Copy message received. ";
                    cd := m.GetLParam(typeof(CopyDataStruct)) as CopyDataStruct;
                    TextBox1.AppendText(cd.cbData.ToString);
                    for i := 0 to 10 do
                      TextBox1.AppendText(', ' + cd.lpData[i].ToString);
                  end
  end;
  inherited WndProc(var m);
end;

When using this code, the array I get at the receiving end is garbage. Anyone know what I'm doing wrong?