对于应用程序，有时候可能需要判断某个文件是否已经被打开，也就是指是否被某个流连接着。这在对文件的读写比较频繁的程序中尤为重要，因为一个文件同一时刻只能有一个流连接的。下面的代码也许能有所帮助。

 public class FileStatus
    {
        [DllImport("kernel32.dll")]
        private static extern IntPtr _lopen(string lpPathName, int iReadWrite);

        [DllImport("kernel32.dll")]
        private static extern bool CloseHandle(IntPtr hObject);

        private const int OF_READWRITE = 2;

        private const int OF_SHARE_DENY_NONE = 0x40;

        private static readonly IntPtr HFILE_ERROR = new IntPtr(-1);

        public static int FileIsOpen(string fileFullName)
        {
            if (!File.Exists(fileFullName))
            {
                return -1;
            }

            IntPtr handle = _lopen(fileFullName, OF_READWRITE | OF_SHARE_DENY_NONE);

            if (handle == HFILE_ERROR)
            {
                return 1;
            }

            CloseHandle(handle);

            return 0;
        }
    }

测试：

    class Program
    {
        static void Main(string[] args)
        {
            string testFilePath = AppDomain.CurrentDomain.SetupInformation.ApplicationBase + @"testOpen.txt";

            FileStream fs = new FileStream(testFilePath, FileMode.OpenOrCreate, FileAccess.Read);

            BinaryReader br = new BinaryReader(fs);

            br.Read();

            Console.WriteLine("文件被打开");

            int result =FileStatus.FileIsOpen(testFilePath);

            Console.WriteLine(result);

            br.Close();

            Console.WriteLine("文件被关闭");

            result = FileStatus.FileIsOpen(testFilePath);

            Console.WriteLine(result);

            Console.ReadLine();
        }
    }

结果：

代码下载：http://download.csdn.net/detail/yysyangyangyangshan/4914142