抓取用户取消http文件下载的C#方法

 /// <summary>
        /// 输出硬盘文件，提供下载
        /// </summary>     
        /// <param name="context">HttpContext对象</param>
        /// <param name="_fullPath">要下载的文件的完整路径</param>
        /// <returns>是否成功</returns>
        public static bool ResponseFile(HttpContext context, string _fullPath)
        {
            HttpRequest _Request = context.Request;
            HttpResponse _Response = context.Response;
            string strFileName = new FileInfo(_fullPath).Name;
            try
            {
                FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                BinaryReader br = new BinaryReader(myFile);
                try
                {
                    _Response.AddHeader("Accept-Ranges", "bytes");
                    _Response.Buffer = false;
                    long fileLength = myFile.Length;
                    long startBytes = 0;

                    int pack =10240 ; //10K bytes       进行拆包,每包大小
                    if (_Request.Headers["Range"] != null)
                    {
                        _Response.StatusCode = 206;
                        string[] range = _Request.Headers["Range"].Split(new char[] { '=', '-' });
                        startBytes = Convert.ToInt64(range[1]);
                    }
                    _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
                    if (startBytes != 0)
                    {
                        _Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength - 1, fileLength));
                    }
                    _Response.AddHeader("Connection", "Keep-Alive");
                    _Response.ContentType = "application/octet-stream";
                    _Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(strFileName, System.Text.Encoding.UTF8));

                    br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
                    int maxCount = (int)Math.Floor(Convert.ToDouble( (fileLength - startBytes) / pack)) + 1;

                    for (int i = 0; i < maxCount; i++)
                    {
                        if (_Response.IsClientConnected)
                        {
                            _Response.BinaryWrite(br.ReadBytes(pack));
                            _Response.Flush();
                        }
                        else
                        {                            
                            i = maxCount;
                            SqlHelp.SaveLog.WriteLog("用户取消下载!");
                        }
                    }
                }
                catch
                {
                    return false;
                }
                finally
                {
                    br.Close();
                    myFile.Close();
                }
            }
            catch( Exception ex)
            {
                return false;
            }
            return true;
        }