Delphi XE DLL在c#中.带WideString的编组结构

Delphi dll中的代码:

...
type
  TPrototype = packed record
    TypeControl: Integer;
    Left: Integer;
    Top: Integer;
    Width: Integer;
    Height: Integer;
    Name: WideString;
    Caption: WideString;
  end;
...
procedure AssignPrototype(var Prototype: TPrototype); stdcall;
begin
  FillChar(Prototype, SizeOf(Prototype), 0);
  with Prototype do begin
    TypeControl := 1;
    Left   := 10;
    Top    := 20;
    Height := 30;
    Width  := 30;
    Caption := 'mycaption';
    Name := 'myname'
  end;
end;
...
exports
 AssignPrototype;
begin
end.

和c#中的代码:

...
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode, Pack=1)]
        public struct Prototype
        {
                public Int32 TypeControl;
                public Int32 Left;
                public Int32 Top;
                public Int32 Width;
                public Int32 Height;
                [MarshalAs(UnmanagedType.BStr)]
                public string Name;
                [MarshalAs(UnmanagedType.BStr)]
                public string Caption;
        }
...
[DllImport("DLL.dll", CallingConvention=CallingConvention.StdCall]
public static extern void AssignPrototype(ref Prototype prototype);
...

但是它不起作用。如果在Delphi 7中Name and Caption是一个数组[1..]50]的Char和我使用[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]它的工作，但最多256个字符是非常少的和名称，标题与西里尔字符是空的。