c# 不同窗体之间传值和调用

 //声明一个委托
        public delegate void DisplayUpdateDelegate(string str);
        //声明事件
        public event DisplayUpdateDelegate ShowUpdate;
        private void Form2_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (ShowUpdate != null)
            {
                ShowUpdate(textBox1.Text.ToString());
            }
        }

   private void button3_Click(object sender, EventArgs e)
        {
            Form2 _frm2 = new Form2();
            _frm2.ShowUpdate += new Form2.DisplayUpdateDelegate(ShowMessage);
            _frm2.Show();
        }

        private void ShowMessage(string str)
        {
            textBox1.Text = str;
        }

  public delegate void ChangeSonWindowDelegate(string str);
        ChangeSonWindowDelegate _changeSonWindow;
        private void button1_Click(object sender, EventArgs e)
        {

            Form2 _frm2 = new Form2();
             _changeSonWindow = new ChangeSonWindowDelegate(_frm2.ShowMessage);
            _frm2.Show();

        }
     
        private void button2_Click(object sender, EventArgs e)
        {

            _changeSonWindow(textBox1.Text);

        }

        public void ShowMessage(string str)
        {
            textBox1.Text = str;

        }