父窗體：
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //事件處理方法
        void frm_TransfEvent(string value)
        {
            textBox1.Text = value;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 frm 
 
= new Form2();
            //註冊事件
            frm.TransfEvent += frm_TransfEvent;
            frm.ShowDialog();
        }
    }
    
子窗體：
    public delegate void TransfDelegate(String value);
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        
 
public event TransfDelegate TransfEvent;

        private void button1_Click(object sender, EventArgs e)
        {
            //觸發事件
            TransfEvent(textBox1.Text);
            this.Close();
        }
    }