C#如何定义位(Bit)

[StructLayout(LayoutKind.Explicit, Size=16, CharSet=CharSet.Ansi)]
public class Flag
{
[FieldOffset(0)]
public ushort ReserveBits;
[FieldOffset(1)]
public ushort nFsuVer;
[FieldOffset(2)]
public ushort SrcAddrType;
[FieldOffset(3)]
public ushort DestAddrType;
[FieldOffset(4)]
public ushort PktCommType ;
[FieldOffset(6)]
public ushort PktDataType;
[FieldOffset(8)]
public ushort n485Addr;

};