异步委托实现多线程winform控件编程

private void button1_Click(object sender, EventArgs e)
{
    ThreadStart ts = new ThreadStart(add);
    Thread th = new Thread(ts);
    th.Start();
 }

delegate void changText(string ss);

void add()
{
   int a = 1;
   int b = 2;
   string sum = Convert.ToString(a + b);
   // 计算完成需要在一个文本框里显示
   this.BeginInvoke(new changText(intoText), sum);
}

void intoText(string sum)
{
   if (this.InvokeRequired)
   {
      this.BeginInvoke(new changText(intoText), sum);
   }
   else
   {
      textBox1.Text = sum;
   }
}