how to correctly use the attribute "FieldOffset" in .Net Compact Framework

Question

recently,I wrote some codes,but there is something wrong in my programme.some of codes follow: using System.Runtime.InteropServices; [StructLayout(LayoutKind.Explicit)] public class MyUnion { [FieldOffset(0)] G00 g00; [FieldOffset(0)] G01 g01; [FieldOffset(0)] G02_G03 g02_g03; [FieldOffset(0)] G12 g12; [FieldOffset(0)] ellips g12_g13; [FieldOffset(0)] g16type g16; [FieldOffset(0)] G04 g04; [FieldOffset(0)] G31 g31; [FieldOffset(0)] G33 g33; [FieldOffset(0)] G87 g87; [FieldOffset(0)] G88 g88; [FieldOffset(0)] S s; public MyUnion() { // // TODO: ??????????? // } } And the wrong information belows: C:\Documents and Settings\gr\My Documents\Visual Studio Projects\GL2000_32bit\FunctionStruct.cs(1063): can not find the class or namespace“FieldOffset”(lack using .....?) But the same code is right in .Net Framework.So is there anyone who can help to resolve the problem? Thank you!