ASP.NET: Warning on changed data closing windows

Question

I\'d like to warn users when they try to close a browser window if they didn\'t save the changes they made in the web form.

I\'m us

Answer 1

Simply add the window.onbeforeunload event. This shows up a modal window where you can decide to stay or leave the page.

window.onbeforeunload = function (event) {
  var message = 'All changes will get lost!';
  if (typeof event == 'undefined') {
    event = window.event;
  }
  if (event) {
    event.returnValue = message;
  }
  return message;
}

All browsers will provide a standard message ("Are you sure you want to navigate away from this page?") plus your custom message.

So the window will look like this:

---------------------------------
| Are you sure you want to      |
| navigate away from this page? |
|                               |
| All changes will get lost!    |
|                               |
|     [Cancel]     [Ok]         |
---------------------------------