timer implementation in asp.net

Timer can also be used at ClientSide using the following Code:

var _timer;
function StartTimer() {
    if (_timer == null) {
        var timeInterval = document.getElementById("hdnTimeInterval").value;
        var timeValue = document.getElementById(timeInterval).value;
        if (timeValue != null || timeValue != undefined) {
            _timer = window.setInterval(EndTimer, timeValue);
        }
    }
}

function EndTimer() {
    if (_timer != null) {
        window.clearInterval(_timer);
        _timer = null;
    }
}

hdnTimeInterval - will be your time interval in milliseconds

window.setInterval - Is used to call a function on reaching the set time interval.
In the above case I have called EndTimer function to end the timer.

Hope this will be useful.

DaniWeb article is a good reference for you. http://www.daniweb.com/web-development/aspnet/threads/39568/asp.net-timer-control[^]

Refer this:

http://forums.asp.net/t/1757336.aspx/1[^]

This question may help:
How to implement countdown timer in asp.net using c#[^]

Try this:

Add to the aspx file between the <form> tags:

<input type="hidden" id="timeAllocated" name="timeAllocated" value="30" runat="server">

That adds this to the CodeBehind file:

protected System.Web.UI.HtmlControls.HtmlInputHidden timeAllocated;

You can then set the timeAlloted control in Page_Load:

if ( !IsPostBack )
       timeAllocated.Value = value-from-database.ToString();

Then add this JavaScript:

<script language="JavaScript">
</script>

Also refer following threads:
countdown timer for online exam[^]
Create Online Exam Project with ASP.Net & C#.Net with JavaScript Timer[^]

[EDIT]
Timer Class[^] Provides a mechanism for executing a method at specified intervals.
Timer Class[^] Performs asynchronous or synchronous Web page postbacks at a defined interval.

Just some help to help you help yourself in the future ;).

Here is a link to CP's site search along with some convenient parameters:
CP's site search for "online examination" searching only the Q&A.[^]. There are over 100 hits in Q&A alone.

This type of question regarding online examination question pops up quite frequently here on CP. Also the nature of all online examination systems is the need that a requirement of some sort of timing has to be met.

Regards,

Manfred