In asp.net-mvc, how can I avoid or alert people from editing the same form or trying to edit stale data?

I have an asp.net-mvc site and I have a web page where you can see a a list of orders.

You can double click on a row and that will open up a detail page (an entitled user will see a large form with lot of text boxes, text areas, radio buttons, etc)

Originally there was only 1 entitled person to an order so no issues but now the users are forming teams and in some cases there are several people (10+) that are entitled to edit the same order so they may have the detail web page up at the same time.

There are 2 issues that now exists.

1. People are now complaining that they are making changes that are immediately getting overridden because other people are editing the same orders at the same time and its creating a lot of confusion.

2. If people are leaving the detail page up all day, they might have a very old version of the view (as multiple other people may have saved changes throughout the day). Nothing notified them that there version of the page is out of date and then should refresh the page before editing.

I am looking for suggestions on the best way to deal with the 2 issues above.

Also, if there are certain libraries or patterns that can be leveraged (versus building something from scratch).