C#实现倒计时

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一、效果

二、实现代码

DateTime dtNow, dtSet;//定义两个DateTime类型的变量，分别用来记录当前时间和设置的到期时间
private void Form1_Load(object sender, EventArgs e)
{
    timer1.Interval = 1000;//设置timer1计时器的执行时间间隔
    timer1.Enabled = true;//启动timer1计时器
    numericUpDown1.Value = DateTime.Now.Hour;//显示当前时
    numericUpDown2.Value = DateTime.Now.Minute;//显示当前分
    numericUpDown3.Value = DateTime.Now.Second;//显示当前秒
}

private void button1_Click(object sender, EventArgs e)
{
    if (button1.Text == "设置")//判断按钮的文本是否为设置
    {
        button1.Text = "停止";//设置按钮的文本为停止
        timer2.Start();//启动timer2计时器
    }
    else if (button1.Text == "停止")//判断按钮的文本是否为停止
    {
        button1.Text = "设置";//设置按钮的文本为设置
        timer2.Stop();//停止timer2计时器
        label3.Text = "倒计时已取消";
    }
}

private void timer1_Tick(object sender, EventArgs e)
{
    label7.Text = DateTime.Now.ToLongTimeString();//显示系统时间
    dtNow = Convert.ToDateTime(label7.Text);//记录系统时间
}

private void numericUpDown2_ValueChanged(object sender, EventArgs e)
{

}

private void groupBox1_Enter(object sender, EventArgs e)
{

}

private void timer2_Tick(object sender, EventArgs e)
{
    //记录设置的到期时间
    dtSet = Convert.ToDateTime(numericUpDown1.Value + ":" + numericUpDown2.Value + ":" + numericUpDown3.Value);
    //计算倒计时
    long countdown = DateAndTime.DateDiff(DateInterval.Second, dtNow, dtSet, FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFourDays);
    if (countdown > 0)//判断倒计时时间是否大于0
        label3.Text = "倒计时已设置，剩余" + countdown + "秒";//显示倒计时
    else
        label3.Text = "倒计时已到";
}