How to Manage Sessions with WinodwNo in asp.net core mvc

Question

I'm working on an application that multiple users log into it on the same server its like a POS web application so we have lets say list of items in invoice I stored the list of items in session so that it wont be stored in the database until the user wants to save it to manage the lists of items for each user I add the WindowNo attribute to the list so there wont be any conflicts between users Now I'm facing the problem of the user opening the same window in the browser using duplicate the Session data will be wrong cause it contains to sessions not one is there any way to solve the problem