C# 解锁从互联网下载的需要右键属性“解除锁定”的文件

一、代码实现

1、AlternateDataStream.cs

using System;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace FileUnlockOnNtfsTool.Common
{
    /// <summary>
    /// NTFS文件系统，文件替代流操作方法类
    /// </summary>
    internal static class AlternateDataStream
    {
        public const int _MaxPath = 256;
        private const string _LongPathPrefix = @"\?";
        public const char _StreamSeparator = ':';

        private static readonly char[] InvalidStreamNameChars = Path.GetInvalidFileNameChars().Where(c => c < 1 || c > 31).ToArray();

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, BestFitMapping = false, ThrowOnUnmappableChar = true)]
        private static extern int FormatMessage(
            int dwFlags,
            IntPtr lpSource,
            int dwMessageId,
            int dwLanguageId,
            StringBuilder lpBuffer,
            int nSize,
            IntPtr vaListArguments);

        [DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)]
        private static extern int GetFileAttributes(string fileName);

        [DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool DeleteFile(string name);

        /// <summary>
        /// 建立流路径
        /// </summary>
        /// <param name="filePath">文件全名</param>
        /// <param name="streamName">流名称</param>
        /// <returns></returns>
        public static string BuildStreamPath(string filePath, string streamName)
        {
            if (string.IsNullOrEmpty(filePath))
                return string.Empty;

            string result = filePath;
            int length = result.Length;
            while (0 < length && '\' == result[length - 1])
            {
                length--;
            }

            if (length != result.Length)
            {
                result = 0 == length ? "." : result.Substring(0, length);
            }

            result += _StreamSeparator + streamName + _StreamSeparator + "$DATA";

            if (_MaxPath <= result.Length && !result.StartsWith(_LongPathPrefix))
            {
                result = _LongPathPrefix + result;
            }

            return result;
        }

        /// <summary>
        /// 校验是否有效流名称
        /// </summary>
        /// <param name="streamName"></param>
        public static bool ValidateStreamName(string streamName)
        {
            if (!string.IsNullOrEmpty(streamName) && -1 != streamName.IndexOfAny(InvalidStreamNameChars))
                return false;

            return true;
        }

        public static bool FileExists(string name)
        {
            return -1 != SafeGetFileAttributes(name);
        }

        private static int SafeGetFileAttributes(string name)
        {
            if (string.IsNullOrEmpty(name))
                throw new ArgumentNullException("流路径不能为空");

            return GetFileAttributes(name);
        }

        public static bool SafeDeleteFile(string name)
        {
            if (string.IsNullOrEmpty(name))
                throw new ArgumentNullException("流路径不能为空");

            return DeleteFile(name);
        }
    }
}

2、FileSystem.cs

using System;
using System.IO;

namespace FileUnlockOnNtfsTool.Common
{
    /// <summary>
    /// FileInfo扩展方法
    /// </summary>
    public static class FileSystem
    {
        /// <summary>
        /// 指定替代流在文件中是否存在
        /// </summary>
        /// <param name="file"></param>
        /// <param name="sStreamName"></param>
        /// <returns></returns>
        public static bool AlternateDataStreamExists(this FileSystemInfo file, string sStreamName, out string sStreamPath)
        {
            if (null == file)
                throw new ArgumentNullException("文件不能为空");

            if (!AlternateDataStream.ValidateStreamName(sStreamName))
                throw new ArgumentException("流名称存在无效字符");

            sStreamPath = AlternateDataStream.BuildStreamPath(file.FullName, sStreamName);
            if (string.IsNullOrWhiteSpace(sStreamPath))
                throw new ArgumentException("建立流路径失败，值不能为空");

            return AlternateDataStream.FileExists(sStreamPath);
        }

        /// <summary>
        /// 删除指定替代流
        /// </summary>
        /// <param name="file"></param>
        /// <param name="sStreamName"></param>
        /// <returns></returns>
        public static bool DeleteAlternateDataStream(this FileSystemInfo file, string sStreamName)
        {
            string sStreamPath = "";
            if (!AlternateDataStreamExists(file, sStreamName, out sStreamPath))
                throw new ArgumentException("指定流不存在");

            return AlternateDataStream.SafeDeleteFile(sStreamPath);
        }
    }
}

3、使用

private void btnCheck_Click(object sender, EventArgs e)
        {
            FileInfo file = new FileInfo(txtFile.Text);
            try
            {
                if (!file.Exists)
                {
                    MessageBox.Show("文件不存在");
                    return;
                }

                string sStreamPath = "";
                if (!file.AlternateDataStreamExists(_sZoneId, out sStreamPath))
                {
                    MessageBox.Show("文件未锁定");
                    return;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("文件安全锁验证异常：" + ex.Message);
            }

            try
            {
                if (DialogResult.Yes != MessageBox.Show("文件有安全锁！
是否解除锁定？", "消息", MessageBoxButtons.YesNo, MessageBoxIcon.Information, MessageBoxDefaultButton.Button2))
                    return;

                if (file.DeleteAlternateDataStream(_sZoneId))
                    MessageBox.Show("解锁成功！");
                else
                    MessageBox.Show("解锁失败");
            }
            catch (Exception ex)
            {
                MessageBox.Show("解锁异常：" + ex.Message);
            }
        }

二、扩展阅读

1、甚么是 “alternative data-streams” ？

      Since NT 3.1, the NTFS file system has supported multiple data-streams for files. There has never been built-in support for viewing or manipulating these additional streams, but the Windows API functions include support for them with a special file syntax: Filename.ext:StreamName. Even Win9x machines can access the alternative data streams of files on any NTFS volume they have access to, e.g., through a mapped drive. Because the Scripting.FileSystemObject and many other libraries call the CreateFile API behind the scenes, even scripts have been able to access alternative streams quite easily (although enumerating the existing streams has always been tricky).

2、为什么非要用Win32API，原生C#实现不了功能么？

      In .NET, however, it seems someone decided to add some checking to the format of filenames. If you attempt to open a FileStream on an alternative stream, you will get a "Path Format not supported" exception. I have been unable to find any class in the CLR that provides support for alternative data streams, so I decided to roll my own.

借鉴出处：https://www.codeproject.com/Articles/2670/Accessing-alternative-data-streams-of-files-on-an