title: How to check whether the new line is created but not saved yet
body: <p>Which FormDataSource method to use to determine that the record is not saved yet?
  </p>
  
  <p>i.e. </p>
  
  <p><img src="https://i.stack.imgur.com/aK2Bu.png" alt="enter image description here"></p>
  
  <p></p>
  
  <p>I mean when my grid line is in this situation I want my mennuItemButton to throw the error.
  </p>
  
  <p>Thanks...</p>