AJAX asp.net中的计时器问题

Question

I am developing an web application where i need a count down timer. Im using asp.net

asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>

    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:Label ID="lblHour" Text="" runat="server"></asp:Label>
        <asp:Label ID="lblMin" Text="" runat="server"></asp:Label>
        <asp:Label ID="lblSec" Text="" runat="server"></asp:Label>
        <asp:Timer ID="Timer1" runat="server" Interval="1000" ontick="timer_Tick">
        </asp:Timer>

    </ContentTemplate>


    </asp:UpdatePanel>

Code behind

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        Session["time"] = DateTime.Now.AddSeconds(40);
    }


}

protected void timer_Tick(object sender, EventArgs e)
{
    TimeSpan time1 = new TimeSpan();
    time1 = (DateTime)Session["time"] - DateTime.Now;
    if (time1.Seconds <= 0)
    {
        lblSec.Text = "TimeOut!";
    }
    else
    {
        lblSec.Text = time1.Seconds.ToString();
    }


}

The problem i am having is, the timer wont decrement properly. It starts with 38, then goes to 35 then 32 and so on.

Is there a way to fix this problem?

Answer 1

I reckon the issue here is that when timer is triggered, the time it executes the code, it is little longer then one sec, 1 sec + some micro seconds, this is the cause of this output. Test this in your code.

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Session["time"] = DateTime.Now.AddSeconds(40);
        }
    }

    protected void timer_Tick(object sender, EventArgs e)
    {
        var endTime = (DateTime) Session["time"];
        var endMin = ((DateTime)Session["time"]).Minute;
        var endSec = ((DateTime)Session["time"]).Second;
        var endMsec = ((DateTime)Session["time"]).Millisecond;
        var currentTime = DateTime.Now;
        var currentMin = currentTime.Minute;
        var currentSec = currentTime.Second;
        var currentMsec = currentTime.Millisecond;

        var time1 = endTime - currentTime;

        lblHour.Text = string.Format("End Sec - {0}:{1}:{2}", endMin, endSec, endMsec);
        lblMin.Text = string.Format("Current Sec - {0}:{1}:{2}", currentMin, currentSec, currentMsec);

        lblSec.Text = time1.Seconds <= 0 ? "TimeOut!" : time1.Seconds.ToString();
    }