C# 解锁从互联网下载的需要右键属性“解除锁定”的文件

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);
        }
    }
}

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);
        }
    }
}

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！\n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);
            }
        }