c#得到局域网共享剩余空间

[DllImport( " kernel32.dll " )]
         private   static   extern   bool  GetDiskFreeSpaceEx(
         string  lpDirectoryName,  out   ulong  lpFreeBytesAvailable,  out   ulong  lpTotalNumberOfBytes,  out   ulong  lpTotalNumberOfFreeBytes);

         ///   <summary>
         ///  取得磁盘剩余空间
         ///   </summary>
         ///   <param name="driveDirectoryName"> 驱动器名 </param>
         ///   <returns> 剩余空间 </returns>
         private   ulong  GetFreeSpace( string  driveDirectoryName)
        {
             ulong  freeBytesAvailable, totalNumberOfBytes, totalNumberOfFreeBytes;
            GetDiskFreeSpaceEx(driveDirectoryName,  out  freeBytesAvailable,  out  totalNumberOfBytes,  out  totalNumberOfFreeBytes);
             return  freeBytesAvailable;
        }