WinApp C# ใช้งาน task กับ form แล้ว ค้างตลอดครับ

 void TaskGetFileTask()
        {
            DateTime s = DateTime.Now;
            this.Invoke(new Action(() => {this.Text = "runing...." ;}));
            string[] dir = System.IO.Directory.GetDirectories(@"g:\TestCSharp", "*.*", System.IO.SearchOption.TopDirectoryOnly);
            var tasks = new Task[dir.Length-1];
            this.Invoke(new Action(() => { this.Text = "Getfiles" ; }));
            for (int i = 0; i < dir.Length-1; i++)
            {
                tasks[i] = Task.Run(() => 
                { System.IO.Directory.GetFiles(dir[i], "*.*", System.IO.SearchOption.AllDirectories).ToList<string>()
                    .ForEach(f => { richTextBox1.Invoke(new Action(() => { richTextBox1.Text += "\n" + f; })); });
                });
            }
            try
            {
                Task.WaitAll(tasks);
            }
            catch { }

            richTextBox1.Invoke(new Action(() => { richTextBox1.Text += "\n Status of completed tasks:"; }));
            foreach (var t in tasks)
                richTextBox1.Invoke(new Action(() => { richTextBox1.Text += "\n " + string.Format(" Task #{0}: {1}", t.Id, t.Status); }));


            DateTime ss = DateTime.Now;
            TimeSpan ts = ss-s;
            this.Invoke(new Action(() => { this.Text = "run complete.. Time:" + ts.Hours+":" + ts.Minutes+":" + ts.Seconds + " " + ts.Milliseconds; }));
        }

        void TaskGetFileThread()
        {
            DateTime s = DateTime.Now;
            this.Invoke(new Action(() => { this.Text = "runing...."; }));
            string[] dir = System.IO.Directory.GetDirectories(@"g:\TestCSharp", "*.*", System.IO.SearchOption.TopDirectoryOnly);
            this.Invoke(new Action(() => { this.Text = "Getfiles"; }));
            for (int i = 0; i < dir.Length - 1; i++)
            {
                    System.IO.Directory.GetFiles(dir[i], "*.*", System.IO.SearchOption.AllDirectories).ToList<string>()
                      .ForEach(f => { richTextBox1.Invoke(new Action(() => { richTextBox1.Text += "\n" + f; })); });
            }

            richTextBox1.Invoke(new Action(() => { richTextBox1.Text += "\n Status of completed tasks:"; }));
            DateTime ss = DateTime.Now;
            TimeSpan ts = ss - s;
            this.Invoke(new Action(() => { this.Text = "run complete.. Time:" + ts.Hours + ":" + ts.Minutes + ":" + ts.Seconds + " " + ts.Milliseconds; }));
        }

 new Thread(TaskGetFileTask).Start();
 new Thread(TaskGetFileThread).Start();