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How to do Database changes after user exit from the website?

i have a rental website and when someone wants to make an offer he has 7 min to pay, if he wont pay the offer will delete.
i have a timer on my form to check the time, and when the timer is on 0:00 and the user didn't pay his offer will delete.
MY question is how can i check if user log out? i mean user can exit from the site (by clicking X) and his session will end.
i want to delete his rent offer if user quit from the website.
Thanks for the helpers.

For this scenario, I don't think its a good idea to rely on browser events, such as onunload & onbeforeunload. User may have opened more than one tabs. So closing one tab will remove the offer. Furthermore, if the user click back button these events will be fired. So don't rely on browser events for this.
(But, if the user clicked on LogOut then you have enough information to delete the offer.)
Perhaps you can use following approach to handle your original problem:
When user create a new offer store these details in the database with two extra columns: OfferCreatedUtcDateTime and PaymentCompleted(which should be false).
If the user completed payment successfully, you can set PaymentCompleted to true.
Then you can use one of the following two options:
Option 1:
Create a windows service which will check above database columns. If the PaymentCompleted == false and OfferCreatedUtcDateTime + offer valid period > CurrentUtcDateTime then you can delete this offer.
Option 2:
As mentioned by #nvoigt in the answer, every time user search for a resource you can ignore or delete offers which satisfies the condition mentioned in Option 1.
Hope this helps.

First do not fulfill offers that are older than your timeout(7mins) I'm assuming that you have OfferCreatedDate timeStamp. Second create a job that will clean all unfulfilled and expired offers. Hope this helps

You cannot. Not reliably. The user will not send you a nice message when he does not do something.
You can program your site to send you a signal if something happens, but you need to know when something doesn't happen. And it can "not happen" in multiple ways, many of them not allowing a signal to be transmitted.
Just imagine your user's train goes into a tunnel or he kills his browser, his computer crashes or cell phone loses battery power. All events that happen daily and all of them will not notify you nicely. They cannot.
So what you need to do is figure out a way to delete all obsolete orders. Either on a timer in an independent service, or maybe before a user places any order. But you need do that in a place independent of the user playing nice with your frontend app.
One way of handling this would be to save the date and time of creation with every offer you give out. Every time you check available resources and create a new offer for a user, delete all offers that are older than your limit before giving out new offers, thereby freeing up the blocked resources.

What about not focusing on how to set the timer to 0 when user session end but check other users timer's when another user create one ?
Then you can still have the checking process for the connected user, when it goes to 0 it stopped but for the case the user close the windows or leave, when another user create a reservation you also and firstly check if there's timer still alive older than 7 minutes and you release them so the user currently doing a reservation can do this one that has just been set as available ?

ASP.Net C# Web Form: Prevent new server session while previous is processing

I have an ASP.NET 4.5 web form running C# code behind on a server. A specific form often takes some time to finish while it updates and changes various database records. However, if the user closes the tab or tries to reopen the web form, it will try to check the users status in the database and fail when those later change due to the first running process.
The need is to track this specific instance of the process and user, and if it is still running, prevent the page from loading fully or redirect. I was hoping to find and store some user and process information on a cookie and then simply check for this each time on page_load. I was not able to find these variables/properties.
Am I going about this the right way, and if so, how can I accomplish this?
Thanks!

I was not able to find the exact solution I was looking for. At the moment, I cannot see any way to find a server side identification id of the process.
Instead, I referenced How to tell if a page unload in ASP is a PostBack and made it so that the page would warn when being unloaded before the confirmation screen is shown. As long as the form opens to the same named tab, the user would be given the warning screen and given a confirmation before they could close or reload a new web form instance.

SpicIE toolbar, SHDocVw.IWebBrowser2 execScript problem?

I'm developing an addon for IE8+.
Main function:
- when I click the toolbar, it will display a box inside every single page, ex: google.com, bing.com, codeproject.com... by using execScript to execute jQuery.
Therefore, what Im doing is run javascript in the current page.
Everything has done except when that page perform an Pop-up, it doesnt work anymore.
I click the toolbar, nothing happen, but when I look at the pop-up, surprise! has the box which im trying to display. So, I think the current tab and the popup of its is running the same process.
I have change registry key TabProcGrowth to 20, to make sure every single tab run by its own process, but maybe it not work with popup.
sr for my bad english, any suggestion is welcome.
Thanks in advance.
update:
I have changed the way to develop my addon, so I change my question, too. (But any suggestion for the 1st question still very useful for me).
My new question still mention the "execScript" problem.
HOW to execute javascript with every individual tab of IE browser with TabProcGrowth = 0. I need this value set to 0 because I have the timer to request to the server every interval1 (ex: 60s). So if there are more than one processes of IE, the addon will send multi request to server at the sametime.
In my situation now, I set TabProcGrowth to 0. Open IE, open some tabs. Click the toolbar at the newest tab, it works, ofcourse!. But when I click toolbar at the old one, nothing happen. The script still be execute but it takes effect on the newest tab.
It's the big problem for me, resolve this problem, you guys save my life.

fighting spam bots

I have C# form in the site and want to prevent spam bots from filling it. The trick is, that I want to avoid CAPTHA or any other user input to avoid loosing a single registration.
Here are some techniques I have in my mind:
Hidden input field (question: is this still effective?)
Track time, since the first user input (focus on FirstName) till posting a form.. Humans will take more than 3 seconds to complete a form (even with auto-fill), where bots take a second or less to fill in registration and post it. (question: if I start timer with the first user input, when should I stop it?)
Put in the form tag a fake post url, or post form to itself, and only on Submit button click action to add a real post url with javascript. (question: wonder if new spam bots can cheat this?)
I would be glad to hear other techniques I could adopt, again, without using CAPTCHA, spam filters, form verifications and even validation. Thank you

would be good to have some sort of flash which asks you to reconnect dots (so that it is interactive and doesnt require typing), and when the user does it correctly, you can post with submit to check.
Never liked CAPTCHA, especially the wierd ones where even humans have problem intepreting it :)

A year ago there was a nice control for asp.net that put a hidden field on the form. With a javascript formula. Robots posted it back - and it wanted the result (stored the result first in the session). basically, as robots dont interpret the form in a browser (too slow).... ;) Most got just thrown out there.
Also, another tip: put in hidden fields for the email to address. Some (old)php forms use a mailer supportnig this. OBVIOUSLY only a robot fills that out ;) If not empty -> garbage.
Anyone else have any smart ideas? ;)

I would say stick with Captcha or a similar thing where the user has to type something in.
The problem with using JavaScript is that not everyone has javascript turned on and quite a few have it turned off for various reasons.
Now if you want to really track time, send a hidden form field with the server time filled in. When the postback occurs take the delta of that with the current time. Obviously if the field is missing then you know someone directly posted.

Controlling browser forward/back functions in web application

I'm writing a web-based application for internal use within the business where I work. It's a fairly complex application, with a lot of forms that will allow the user to view and enter data, which once saved will be stored in a database.
One thing I'm anxious to avoid is allowing a situation to exist where a user might enter large amounts of data in the browser, and then (either deliberately or inadvertently) navigate off the page without saving the changes. To this end, I have already implemented an entry page which opens up a new browser window in which there are no navigation controls at all; only what is provided on the web pages themselves.
However, there are two potential ways in which a user could still lose data:
The browser Close button is still enabled, and a user could potentially lose work by clicking it inadvertently. I can probably live with this, as it falls at the extreme end of helping the user not to shoot himself in the foot.
In Internet Explorer (and, apparently, in Firefox) the Backspace button works like a Back button. I only discovered this accidentally, and have as yet been unable to find a simple way of stopping this behaviour. This is potentially a problem, as an inadvertent use of the Delete key (e.g. having positioned the cursor in a read-only textbox, or when the cursor isn't on any particular field in the page) will navigate off the page.
What I would like to do, as a minimum, is prevent Backspace from navigating off a page if that page has any user-writable fields on it and any of those fields have been changed by the user since the form was loaded. Ideally, I would like to disable this particular use of the Backspace key completely, while the user is logged into this web application. The two possible ways that I can think of, for achieving this, are: (1) clear the browser's history as each page is loaded, or (2) trap the Backspace key and only allow it to work if the cursor is positioned within a field whose text can be changed (e.g. a textbox).
Can anyone suggest how I could achieve either of these things? The solution needs to be programmatic, rather than something that has to be manually configured on every browser in the company.

Instead of blocking* functionality that your users have learned to expect in their daily activities at work and at home, why not work with it? Make the "back" button actually take them to the previous screen as expected, and use AJAX to silently save the form as they fill it out (say, every 5 or 10 seconds), so when they return to the form you can check to see if they already have partial, unsubmitted values saved and reload them.
This approach aligns with the realities of web-based applications and delights users if implemented well. An alert that says "you did something wrong" just frustrates users and makes them trust your application less. Remember - users almost never do the wrong thing. It's our applications that aren't aligned with usage.
* more like trying to block functionality. As you've discovered, people who designed the interwebs and web browsers never really intended for site developers to totally disable moving back and forward in the navigation history.

What about something like this? You can ask them if they are sure before they leave.
var changes = false;
window.onbeforeunload =
function()
{
if (changes)
{
var message = "Are you sure you want to navigate away from this page?\n\nYou still have unsaved changes.\n\nPress OK to continue or Cancel to stay on the current page.";
if (confirm(message)) return true;
else return false;
}
}

You should look at the Javascript's window.unload event.
This is fired when the use tries to leave the page. You can't totally stop them leaving the page, but you can give them a chance to cancel.

try this
window.onbeforeunload() {
return "Are you sure you want to navigate away?";
}