public delegate void SetVisiableHandler();//定義委托類型

private void button1_Click(object sender,EventArgs e)//單擊事件，打開子窗體
{
    Form2 frm = new Form2(new SetVisiableHandler(SetVisiable));
    frm.Show();
}

private void SetVisiable()
{
    dataGridView1.Rows.Add("123","456","789");
}

private SetVisiableHandler m_setVisable;//聲明委托變量
public Form2(SetVisiableHandler  setvisiable)
{
    InitializeComponent();
    this.m_setVisiable = setvisiable;
}

public void butten1_Click(object sender,EventArgs e)
{
    if(this.m_setVisiable != null)
    {
        this.m_setVisiable();
    }
}