The most popular ASP.NET shopping cart in the world based on Microsoft technologies: nopCommerce
nopCommerce is an ASP.NET (MVC) database and based on an open-source e-commerce system. With nopCommerce the backend of your webshop is very stable and flexible. The backend database uses MS SQL 2008 (or later versions).
The user-friendly software system has been downloaded more than half a million times. nopCommerce can be used for digital products and services but also for selling physical products. The system targets merchants that have ‘outgrown’ other systems.