C# สอบถาม เรื่องการ เพิ่ม ค่าใน List ขณะที่มีการเรียกใช้ ครับ

namespace Downloader
{
    public class FileLink
    {
        public string FileTarget;
        public string Link;
        public FileLink(string lnk, string f)
        {
            FileTarget = f;Link = lnk;
        }
    }
    public class DownloaderProgress : ProgressBar
    {
        List<FileLink> LinkLoad;
        public long BytesReceived = 0;
        public long TotalBytesToReceive = 0;
        public DownloaderProgress() : base()
        {
            LinkLoad = new List<FileLink>();
            SetStyle(ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint, true);

        }
        #region _EventHandler
       

        public event EventHandler DownloadDataAllCompleted;
        protected virtual void OnDownloadDataAllCompleted(EventArgs e)
        {
            if (DownloadDataAllCompleted != null) DownloadDataAllCompleted(this, e);
        }


        public event DownloaderFileHandler DownloadDataCompleted;
        protected virtual void OnDownloadDataCompleted(DownloaderFileEventArgs e)
        {
            if (DownloadDataCompleted != null) DownloadDataCompleted(this, e);
        }

        public event DownloaderFileHandler DownloadProgressChanged;
        protected virtual void OnDownloadProgressChanged(DownloaderFileEventArgs e)
        {
            if (DownloadProgressChanged != null) DownloadProgressChanged(this, e);

        }
        public event DownloaderFileHandler DownloadError;
        protected virtual void OnDownloadError(DownloaderFileEventArgs e)
        {
            if (DownloadError != null) DownloadError(this, e);

        }
        public event DownloaderFileHandler DownloadFile;
        protected virtual void OnDownloadFile(DownloaderFileEventArgs e)
        {
            if (DownloadFile != null) DownloadFile(this, e);

        }



        public event DownloaderProgressChangedHandler DownloadStatus;
        protected virtual void OnDownloadStatus(DownloaderProgressChangedEventArgs e)
        {
            if (DownloadStatus != null) DownloadStatus(this, e);

        }


        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            // Clear the background.
            e.Graphics.Clear(this.BackColor);
            // Draw the progress bar.
            float fraction = (float)(this.Value - this.Minimum) / (this.Maximum - this.Minimum);

            ProgressBarRenderer.DrawHorizontalBar(e.Graphics, new Rectangle(new Point(0, 0), this.Size));
            ProgressBarRenderer.DrawHorizontalChunks(e.Graphics, new Rectangle(new Point(1, 1),
             new Size((int)(((this.Size.Width - 2) / 100.0) * fraction), this.Size.Height - 2)));

            int wid = (int)(fraction * this.ClientSize.Width);
            e.Graphics.FillRectangle(
                Brushes.LightGreen, 0, 0, wid,
                this.ClientSize.Height);

            // Draw the text.
            e.Graphics.TextRenderingHint =
                TextRenderingHint.AntiAliasGridFit;


            using (StringFormat sf = new StringFormat())
            {
                sf.Alignment = StringAlignment.Center;
                sf.LineAlignment = StringAlignment.Center;

                if (Value == Maximum)
                {
                    e.Graphics.DrawString("Complete...", this.Font, Brushes.Black, this.ClientRectangle, sf);
                }
                else
                {
                    e.Graphics.DrawString((fraction).ToString("0.000 %") + " : " + Value + "/" + Maximum, this.Font, Brushes.Black, this.ClientRectangle, sf);
                }

            }

        }

        #endregion



        public void Add(FileLink lnk)
        {
            LinkLoad.Add(lnk);
            this.Invoke(new Action(() => { try { this.Maximum++; } catch { } }));
        }
        public void Add(string lnk,string Fileload)
        {
            LinkLoad.Add(new FileLink(lnk,Fileload));
            this.Invoke(new Action(() => { try { this.Maximum++; } catch { } }));
        }
        public void AddRange(List<FileLink> lnks)
        {
            LinkLoad.AddRange(lnks);
            this.Invoke(new Action(() => { try { this.Maximum+= LinkLoad.Count; } catch { } }));
        }
        public void Start()
        {
            
            if (LinkLoad == null || LinkLoad.Count <= 0)
            {

                OnDownloadDataAllCompleted(new EventArgs());
                return;
            }
            int complete = 0;
            LinkLoad
                .ForEach(l =>
                {
                    
                        OnDownloadStatus(new DownloaderProgressChangedEventArgs(l.Link, "Downloading...."));
                    string f;
                    if (File.Exists(l.FileTarget))
                    {
                        f = RenameFileDup(l.FileTarget);
                    }
                    else
                    {
                        f = l.FileTarget;
                    }

                    if (!Directory.Exists(Path.GetDirectoryName(l.FileTarget)))
                        Directory.CreateDirectory(l.FileTarget);
                    using (WebClient wc = new WebClient())
                    {
                        wc.DownloadFileCompleted += new AsyncCompletedEventHandler((s, e) =>
                        {
                            this.Invoke(new Action(() => { try { this.Value++; } catch { } }));
                            complete++;
                            OnDownloadStatus(new DownloaderProgressChangedEventArgs(l.Link, "Complete.."));
                            OnDownloadDataCompleted(new DownloaderFileEventArgs(l.Link, f));
                            if (complete >= LinkLoad.Count)
                            {
                                return;

                            }

                        });
                        wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler((s, e) =>
                        {

                            this.Invoke(new Action(() => { this.BytesReceived += (int)e.BytesReceived; }));
                            this.Invoke(new Action(() => { this.TotalBytesToReceive += (int)e.TotalBytesToReceive; }));
                        });
                        try
                        {
                            OnDownloadFile(new DownloaderFileEventArgs(l.Link, f));
                            wc.DownloadFile(new Uri(l.Link), f);
                        }
                        catch (Exception ex)
                        {
                            OnDownloadError(new DownloaderFileEventArgs(l.Link, f + ":" + ex.ToString()));

                        }
                    }
                });


        }


        string RenameFileDup(string _File)
        {
            string stg = _File;
            if (System.IO.File.Exists(_File))
            {
                int i = 1;
                do
                {
                    stg = System.IO.Path.GetDirectoryName(_File) + "\\" + System.IO.Path.GetFileNameWithoutExtension(_File) + "_" + i + System.IO.Path.GetExtension(_File);
                    i++;
                } while (System.IO.File.Exists(stg));
            }
            return stg;
        }

    }
}

       private void Form1_Load(object sender, EventArgs e)
        {

            
            new System.Threading.Thread(() =>
            {

                new List<string>() { "https://wallpaperplay.com/genres/abstract",
                                    "https://wallpaperplay.com/genres/animals",
                                    "https://wallpaperplay.com/genres/anime",
                                    "https://wallpaperplay.com/genres/art",
                                    "https://wallpaperplay.com/genres/cars",
                                    "https://wallpaperplay.com/genres/celebreties",
                                    "https://wallpaperplay.com/genres/city",
                                    "https://wallpaperplay.com/genres/comics",
                                    "https://wallpaperplay.com/genres/flowers",
                                    "https://wallpaperplay.com/genres/games",
                                    "https://wallpaperplay.com/genres/girls",
                                    "https://wallpaperplay.com/genres/holidays",
                                    "https://wallpaperplay.com/genres/horror",
                                    "https://wallpaperplay.com/genres/love",
                                    "https://wallpaperplay.com/genres/men",
                                    "https://wallpaperplay.com/genres/movies",
                                    "https://wallpaperplay.com/genres/music",
                                    "https://wallpaperplay.com/genres/nature",
                                    "https://wallpaperplay.com/genres/other",
                                    "https://wallpaperplay.com/genres/sci-fi",
                                    "https://wallpaperplay.com/genres/space",
                                    "https://wallpaperplay.com/genres/sport",
                                    "https://wallpaperplay.com/genres/textures",
                                    "https://wallpaperplay.com/genres/tv-series",

                }.ForEach(_url =>
                {
                    string fol = Path.GetFileName(_url);
                  
                        _url.GetLinkByURL(@" target=""_blank""" + "\n" + @"               href=""(https://wallpaperplay.com/board/.*?)"">")
                        .ForEach(url =>
                        {

                            url.GetLinkByURL(@"data-src=""(/walls/.*?/.*?.jpg)""")
                              .ForEach(l =>
                              {
                                  downloaderProgress1.Invoke(new Action(() => downloaderProgress1.Add("https://wallpaperplay.com" + l, @"G:\wallpaperplay\" + fol + "\\" + Path.GetFileName(l))));
                                 // TorServices.Net.NetWorkTOR.LoadFByWebClient("https://wallpaperplay.com" + l, @"G:\wallpaperplay\" +fol + "\\" + Path.GetFileName(l));
                              });

                          /*  Invoke(new MethodInvoker(() =>
                            {
                                this.Text = url;
                              
                               richTextBox1.Text += "https://wallpaperplay.com" + string.Join("\nhttps://wallpaperplay.com", url.GetLinkByURL(@"data-src=""(/walls/.*?/.*?.jpg)""")) + "\n";
                            }));*/


                        });
                    downloaderProgress1.Invoke(new Action(() => downloaderProgress1.Start()));
                });

               // downloaderProgress1.Invoke(new Action(() => downloaderProgress1.Start()));
                this.Invoke(new Action(() => this.Text = "Complete..."));
            }).Start();
        }