public partial class Form1 : Form
    {
        int i = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            timer1.Enabled = true;
            timer1.Interval = 1000;
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            i++;
            MessageBox.Show(i.ToString());
            if (i >= 5)
                timer1.Enabled = false;//timer停止
        }
    }