สอบถาม Error "Thread was being aborted" ค่ะ เวลาให้จบการทำงานของ Thread ก่อนกำหนด

Private Sub Sub_ThreadAbort()
    thread.Abort()
    thread.Join()
    Me.Close()
End Sub

Thread th;
        int ii = 0;
        void RunList()
        {
            while ( th.IsAlive)
            {

              this.Invoke(new Action(()=>{this.Text = "Item " + ii;}));
                    ii++;
                    Thread.Sleep(10);
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            ii = 0;
            listBox1.Items.Clear();
            th  = new Thread(new ThreadStart(RunList));
            th.Start();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Thread.Sleep(10); //เพิ่มตัวนี้ลงไป
            th.Abort();
        }