I've recently accomplished an ASP.NET web application which allow their users to access some data in a database, but what I'm afraid of is conflict between these processes like if they were accessing same record in a database do i need to check changes in the record I'm updating and if it was updated stop updating or from the start i have to block other user from changing the record I'm working on ?

At high level you need to implement data lock at record level from DB. It will depend on the DB taht you are working on for exact mechanism to implement. Aslo you need to capture the same from the application and inform the other user who is trying to access the same record.

Sounds like you may want to implement optimistic concurrency.

If you using the wizards to create your controls, this option can be enabled during the creation of the data source.