delegate void SetTextCallback(string text);
        private void textBox1SetText(string str)
        {

            if (this.textBox3.InvokeRequired)
            {

                SetTextCallback d = new SetTextCallback(textBox1SetText);
                this.Invoke(d, new object[] { str });
            }
            else
            {
                this.textBox3.Text = this.textBox3.Text + "\r\n" + str;
            }
        }
        private void Foo()
        {
            textBox1SetText("abc");
        }
        private void button10_Click(object sender, EventArgs e)
        {
            Thread t = new Thread(new ThreadStart(Foo));
            t.Start();
        }