public partial class UcTest : UserControl
    {
        public UcTest()
        {
            InitializeComponent();
        }
        //定義事件
        public event EventHandler UserControlBtnClicked;
        private void btn_Click(object sender, EventArgs e)
        {
            UserControlBtnClicked
 
?.Invoke(sender, new EventArgs());//把按鈕自身作為參數傳遞
        }

       
    }

winform 用戶控件事件的寫法