我在子线程中调用了textBox1，我需要在主线程中定时的把它清空，可以这样写吗？我这个代码是这样的。这样可以吗？多谢老师指点。

  public delegate void MyInvoke(string str);
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            timer1.Start();
            timer2.Start(); 
        }

 public void DoWord()
        {
            MyInvoke mi = new MyInvoke(SetTxt);
            BeginInvoke(mi, new object[] { "timer1" +"   " });
        }
        public void DoWord2()
        {
            MyInvoke mi = new MyInvoke(SetTxt_2);
            BeginInvoke(mi, new object[] { "Z9758" });
        }

 public void SetTxt(string str)
        {
         
            textBox1.Text = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") +"   "+ str ;
            listBox1.Items.Insert(0, DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")+"   "+str);  
        }
        public void SetTxt_2(string str)
        {
            switch (str)
            {       //listBox1.Items.Insert(0, list_name_file);
                case "Z9758": listBox1.Items.Insert(0, DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "      收到aa数据!"); break;
                case "Z9200": listBox1.Items.Insert(0, DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "      收到bb数据!"); break;
            }
        }

 private void timer1_Tick(object sender, EventArgs e)
        {
            timer1.Interval = 1000 * 1;
            Thread thread_timer = new Thread(new ThreadStart(DoWord));
            thread_timer.Start();
        }

 private void timer2_Tick(object sender, EventArgs e)
        {
            if (listBox1.Items.Count > 100)
            {
                listBox1.Items.Clear();  
            }
            timer2.Interval = 1000 * 3;
            Thread thread_timer3 = new Thread(new ThreadStart(DoWord2));
            thread_timer3.Start();
 
        }