用C＃读取GPS数据的基类，适用于wince操作系统[3]

  [StructLayout(LayoutKind.Sequential)] 
   private struct OVERLAPPED
  {
   public int  Internal;
   public int  InternalHigh;
   public int  Offset;
   public int  OffsetHigh;
   public int hEvent;
  } 
  
  [DllImport("coredll.dll")]
  private static extern int CreateFile(
   string lpFileName,                         // 要打开的串口名称
   uint dwDesiredAccess,                      // 指定串口的访问方式，一般设置为可读可写方式
   int dwShareMode,                          // 指定串口的共享模式，串口不能共享，所以设置为0
   int lpSecurityAttributes, // 设置串口的安全属性，WIN9X下不支持，应设为NULL
   int dwCreationDisposition,                // 对于串口通信，创建方式只能为OPEN_EXISTING
   int dwFlagsAndAttributes,                 // 指定串口属性与标志，设置为FILE_FLAG_OVERLAPPED(重叠I/O操作)，指定串口以异步方式通信
   int hTemplateFile                        // 对于串口通信必须设置为NULL
   );
  [DllImport("coredll.dll")]
  private static extern bool GetCommState(
   int hFile,  //通信设备句柄
   ref DCB lpDCB    // 设备控制块DCB
   ); 
  [DllImport("coredll.dll")]
  private static extern bool BuildCommDCB(
   string lpDef,  // 设备控制字符串
   ref DCB lpDCB     // 设备控制块
   );
  [DllImport("coredll.dll")]
  private static extern bool SetCommState(
   int hFile,  // 通信设备句柄
   ref DCB lpDCB    // 设备控制块
   );
  [DllImport("coredll.dll")]
  private static extern bool GetCommTimeouts(
   int hFile,                  // 通信设备句柄 handle to comm device
   ref COMMTIMEOUTS lpCommTimeouts  // 超时时间 time-out values
   ); 
  [DllImport("coredll.dll")] 
  private static extern bool SetCommTimeouts(
   int hFile,                  // 通信设备句柄 handle to comm device
   ref COMMTIMEOUTS lpCommTimeouts  // 超时时间 time-out values
   );
  [DllImport("coredll.dll")]
  private static extern bool ReadFile(
   int hFile,                // 通信设备句柄 handle to file
   byte[] lpBuffer,             // 数据缓冲区 data buffer
   int nNumberOfBytesToRead,  // 多少字节等待读取 number of bytes to read
   ref int lpNumberOfBytesRead, // 读取多少字节 number of bytes read
   ref OVERLAPPED lpOverlapped    // 溢出缓冲区 overlapped buffer
   );
  [DllImport("coredll.dll")] 
  private static extern bool WriteFile(
   int hFile,                    // 通信设备句柄 handle to file
   byte[] lpBuffer,                // 数据缓冲区 data buffer
   int nNumberOfBytesToWrite,     // 多少字节等待写入 number of bytes to write
   ref int lpNumberOfBytesWritten,  // 已经写入多少字节 number of bytes written
   ref OVERLAPPED lpOverlapped        // 溢出缓冲区 overlapped buffer
   );
  [DllImport("coredll.dll")]
  private static extern bool CloseHandle(
   int hObject   // handle to object