C# WinApp WebClient.DownloadFileCompleted ไม่แน่ใจว่าโค้ดผิดตรงไหนครับ

public   class csharphelper_Loder:ProgressBar
    {
public csharphelper_Loder():base()
        {
            SetStyle(ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint, true);
        }
        public event EventHandler DownloadDataCompleted;
        protected virtual void OnDownloadDataCompleted(EventArgs e)
        {
            if (DownloadDataCompleted != null) DownloadDataCompleted(this, e);
        }
        public delegate void _DownloadDataCompletedEventHandler(object sender, EventArgs e);
        public event EventHandler DownloadProgressChanged;
        protected virtual void OnDownloadProgressChanged(EventArgs e)
        {
            if (DownloadProgressChanged != null) DownloadProgressChanged(this, e);
        }
        public delegate void _DownloadProgressChangedEventHandler(object sender, EventArgs 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);
                }

            }

        }
string getHTML(string url)
        {


            string html = "";
            try
            {
                System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(url.Trim());
                System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.GetResponse();
                System.IO.StreamReader sr = new System.IO.StreamReader(response.GetResponseStream());
                html = sr.ReadToEnd();
                sr.Close();
                response.Close();
            }
            catch { }
            return html;
        }

         public async void Start()
        {
            int min = 1, max = 300;
            Minimum = min;
            Maximum = max;
            await Task.Run(() =>
            {
                string fol = @"G:\csharphelper_Code";
                System.IO.Directory.CreateDirectory(fol);
                int i = 1;

                do
                {
                    int complete = 0;
                    string html = Program.getHTML("http://csharphelper.com/blog/page/" + i + "/");
                    MatchCollection _m = new Regex(@"a href=""(http://www.csharphelper.com/.*?\.zip)""><img border=", RegexOptions.None).Matches(html);
                    if (_m.Count <= 0)
                    {
                        i++;
                        try { this.Invoke(new Action(() => this.Value++)); } catch { }
                    }
                    else
                    {
                        foreach (Match myMatch in _m)
                        {
                            if (!System.IO.File.Exists(fol + System.IO.Path.GetFileName(myMatch.Groups[1].Value)))
                            {
                                using (WebClient wc = new WebClient())
                                {
                                    wc.DownloadFileCompleted += new System.ComponentModel.AsyncCompletedEventHandler((s, e) =>
                                    {
                                        complete++;
                                        if (complete >= _m.Count)
                                        {
                                            System.Threading.Thread.Sleep(500);
                                            i++;
                                            try { this.Invoke(new Action(() => this.Value++)); } catch { }
                                        }
                                    });
                                    wc.DownloadFileAsync(new Uri(myMatch.Groups[1].Value), fol + @"\" + System.IO.Path.GetFileName(myMatch.Groups[1].Value));

                                }
                            }
                            else
                            {
                                i++;
                                try { this.Invoke(new Action(() => this.Value++)); } catch { }
                            }
                        }
                    }
                    


                } while (i <= max);


            });

        }


    }

 wc.DownloadFile(new Uri(myMatch.Groups[1].Value), fol + @"\" + System.IO.Path.GetFileName(myMatch.Groups[1].Value));

var dtasks = new List<Task>();
                        foreach (Match myMatch in _m)
                        {
                            if (!System.IO.File.Exists(fol + @"\" + System.IO.Path.GetFileName(myMatch.Groups[1].Value)))
                            {
                                sUrl = myMatch.Groups[1].Value;
                                sLog = string.Format("Downloading Page {0} /  {1}\n", i, sUrl);
                                Debug.WriteLine(sLog);
                                

                                try
                                {
                                    var wc = new WebClient();
                                    dtasks.Add(wc.DownloadFileTaskAsync(new Uri(myMatch.Groups[1].Value), fol + @"\" + System.IO.Path.GetFileName(myMatch.Groups[1].Value)));
                                }
                                catch (Exception ex)
                                {
                                    Debug.WriteLine(ex.Message);
                                }
                            }
                        }
                        if (dtasks.Count > 0)
                        {
                            try
                            {
                                Task.WaitAll(dtasks.ToArray());
                                sLog = string.Format("Download completed Page {0}\n", i);
                                Debug.Print(sLog);
                            }
                            catch (Exception ex)
                            {
                                Debug.WriteLine("WaitAll Failed");
                                Debug.WriteLine(ex.Message);
                                for (int taskNo = 0; taskNo < dtasks.Count; taskNo++)
                                {
                                    Debug.Print("{0}: Status: {1}, IsFaulted: {2}", 
                                        taskNo, dtasks[taskNo].Status, dtasks[taskNo].IsFaulted);
                                }
                            }
                        }