facing an issue while downloading files using WebClient - ManualResetEvent

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C#

the code below works fine let's say i have a three files to download the first 2 is 2MB and the third is 12MB it downloads all the files correctly but after downloading the first 2 files it fires downloadfilecompleted event but after the third file it doesn't fire.
if i try to move this file or doing anything to it >> it's used by another process
and it never completes until i stop the debugging
after i stop debugging i look at the third file it's downloaded correctly
so i dunno why this event is not firing after downloading this file
i used breakpoints through all code and it seems that there's no exception is thrown
but the scenario here is the thread is frozen after downloading this third file.

Note: this file is not invalid file or corrupted file it's fine i downloaded it with browser,download tools,etc it's fine and the application also downloads it fine.

my code :

#region private fields
        private bool isFinished = false;
        private List<DownloadFileInfo> downloadFileList = null;
        private List<DownloadFileInfo> allFileList = null;
        private ManualResetEvent evtDownload = null;
        private ManualResetEvent evtPerDonwload = null;
        private static WebClient clientDownload;
        long total = 0;
        long nDownloadedTotal = 0;
#endregion

#region The ConStructor of DownloadProgress
        public DownloadProgress(List<DownloadFileInfo> downloadFileListTemp)
        {
            PureEye.DailyOperation.FrmMain.UpdateStatus = 1;
            InitializeComponent();

            this.downloadFileList = downloadFileListTemp;
            allFileList = new List<DownloadFileInfo>();
            foreach (DownloadFileInfo file in downloadFileListTemp)
            {
                allFileList.Add(file);
            }
        }
        #endregion

private void OnFormLoad(object sender, EventArgs e)
        {
            evtDownload = new ManualResetEvent(true);
            evtDownload.Reset();
            ThreadPool.QueueUserWorkItem(new WaitCallback(this.ProcDownload));
        }

private void ProcDownload(object o)
        {
            string tempFolderPath = Path.Combine(CommonUnitity.SystemBinUrl, ConstFile.TEMPFOLDERNAME);
            if (!Directory.Exists(tempFolderPath))
            {
                Directory.CreateDirectory(tempFolderPath);
            }


            evtPerDonwload = new ManualResetEvent(false);
            long totalfilesize = 0;
            foreach (DownloadFileInfo file in this.downloadFileList)
            {
                total += file.Size;
            }
            try
            {
                while (!evtDownload.WaitOne(0, false))
                {
                    if (this.downloadFileList.Count == 0)
                        break;

                    DownloadFileInfo file = this.downloadFileList[0];
                    totalfilesize = file.Size;
                    //progressBarCurrent.Maximum = totalfilesize;

                    //Debug.WriteLine(String.Format("Start Download:{0}", file.FileName));

                    this.ShowCurrentDownloadFileName(file.FileName);

                    //Download
                    clientDownload = new WebClient();
                    NetworkCredential objCred = new NetworkCredential();
                    objCred.UserName = ftpUserID;
                    objCred.Password = ftpPassword;
                    //Added the function to support proxy

                    clientDownload.Proxy.Credentials = objCred;
                    clientDownload.Credentials = objCred;
                    //End added

                    clientDownload.DownloadProgressChanged += (object sender, DownloadProgressChangedEventArgs e) =>
                    {
                        try
                        {
                            int filePercentage = (int)(e.BytesReceived * 100 / totalfilesize);
                            int totalPercentage = (int)((nDownloadedTotal + e.BytesReceived) * 100 / total);

                            this.SetProcessBar(filePercentage, totalPercentage);
                        }
                        catch
                        {
                            //log the error message,you can use the application's log code
                        }

                    };
                    clientDownload.DownloadFileCompleted += (object sender, AsyncCompletedEventArgs e) =>
                    {
                        try
                        {
                            DealWithDownloadErrors();
                            DownloadFileInfo dfile = e.UserState as DownloadFileInfo;
                            nDownloadedTotal += dfile.Size;
                            this.SetProcessBar(0, (int)(nDownloadedTotal * 100 / total));
                            evtPerDonwload.Set();
                        }
                        catch (Exception)
                        {
                            //log the error message,you can use the application's log code
                        }

                    };

                    evtPerDonwload.Reset();

                    //Download the folder file
                    string tempFolderPath1 = CommonUnitity.GetFolderUrl(file);
                    if (!string.IsNullOrEmpty(tempFolderPath1))
                    {
                        tempFolderPath = Path.Combine(CommonUnitity.SystemBinUrl, ConstFile.TEMPFOLDERNAME);
                        tempFolderPath += tempFolderPath1;
                    }
                    else
                    {
                        tempFolderPath = Path.Combine(CommonUnitity.SystemBinUrl, ConstFile.TEMPFOLDERNAME);
                    }

                    clientDownload.DownloadFileAsync(new Uri(file.DownloadUrl), Path.Combine(tempFolderPath, file.FileFullName), file);
                    //Wait for the download complete
                    evtPerDonwload.WaitOne();
                    clientDownload.Dispose();
                    clientDownload = null;

                    //Remove the downloaded files
                    this.downloadFileList.Remove(file);
                }

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                ShowErrorAndRestartApplication();
                //throw;
            }

            //When the files have not downloaded,return.
            if (downloadFileList.Count > 0)
            {
                return;
            }

            //Test network and deal with errors if there have 
            DealWithDownloadErrors();

            //Debug.WriteLine("All Downloaded");
            foreach (DownloadFileInfo file in this.allFileList)
            {
                string tempUrlPath = CommonUnitity.GetFolderUrl(file);
                string oldPath = string.Empty;
                string newPath = string.Empty;
                try
                {
                    if (!string.IsNullOrEmpty(tempUrlPath))
                    {
                        oldPath = Path.Combine(CommonUnitity.SystemBinUrl + tempUrlPath.Substring(1), file.FileName);
                        newPath = Path.Combine(CommonUnitity.SystemBinUrl + ConstFile.TEMPFOLDERNAME + tempUrlPath, file.FileName);
                    }
                    else
                    {
                        oldPath = Path.Combine(CommonUnitity.SystemBinUrl, file.FileName);
                        newPath = Path.Combine(CommonUnitity.SystemBinUrl + ConstFile.TEMPFOLDERNAME, file.FileName);
                    }

                    //just deal with the problem which the files EndsWith xml can not download
                    System.IO.FileInfo f = new FileInfo(newPath);
                    if (!file.Size.ToString().Equals(f.Length.ToString()) && !file.FileName.ToString().EndsWith(".xml"))
                    {
                        ShowErrorAndRestartApplication();
                    }


                    //Added for dealing with the config file download errors
                    string newfilepath = string.Empty;
                    if (newPath.Substring(newPath.LastIndexOf(".") + 1).Equals(ConstFile.CONFIGFILEKEY))
                    {
                        if (System.IO.File.Exists(newPath))
                        {
                            if (newPath.EndsWith("_"))
                            {
                                newfilepath = newPath;
                                newPath = newPath.Substring(0, newPath.Length - 1);
                                oldPath = oldPath.Substring(0, oldPath.Length - 1);
                            }
                            File.Move(newfilepath, newPath);
                        }
                    }
                    //End added

                    if (File.Exists(oldPath))
                    {
                        MoveFolderToOld(oldPath, newPath);
                    }
                    else
                    {
                        //Edit for config_ file
                        if (!string.IsNullOrEmpty(tempUrlPath))
                        {
                            if (!Directory.Exists(CommonUnitity.SystemBinUrl + tempUrlPath.Substring(1)))
                            {
                                Directory.CreateDirectory(CommonUnitity.SystemBinUrl + tempUrlPath.Substring(1));


                                MoveFolderToOld(oldPath, newPath);
                            }
                            else
                            {
                                MoveFolderToOld(oldPath, newPath);
                            }
                        }
                        else
                        {
                            MoveFolderToOld(oldPath, newPath);
                        }

                    }
                }
                catch (Exception exp)
                {
                    //log the error message,you can use the application's log code
                }

            }

            //After dealed with all files, clear the data
            this.allFileList.Clear();

            if (this.downloadFileList.Count == 0)
                Exit(true);
            else
                Exit(false);

            evtDownload.Set();
        }