Windows和Web应用程序C＃asp.net之间的并发

I am wondering if there is a best practice in regards to concurrency between asp.net and a windows app using the same db? I have a db with items their quantity, any of these items can be sold with different quantities from a website shopping cart or store location. updating the item quantity when user adds the item to their shopping cart seems to be a problematic approach.I am wondering if there is a best practice in r