title: Handle multiple users update a same form in web application
body: <p>Suppose user A has open a form with populated data. </p>
  
  <p>While user A do modifications to the form data, user B opens the same form with data populated for user A. </p>
  
  <p>Then while user B doing the modification to the data, user A has click on submit the form which updated the record. </p>
  
  <p>So now when user B finish update the form and click on submit button, a warning message should display that this record been already modified while he is doing modification to the data so he can reload the form again. </p>
  
  <p>I guess this is the best solution(warning message) in user perspective for this kind of situation right? So how to achieve this in back end?</p>