Plugin - nopCommerce
nopCommerce Documentation
https://www.nopcommerce.com/en
nopCommerce is an open-source eCommerce solution based on Microsoft's ASP.NET Core framework and MS SQL Server Database. It provides a catalog frontend and an administration tool backend, allowing shopping cart creation.
nopCommerce is plugable solution. Here we implement plugin for adding new features. Plugin can be used in multiple sites. So, it helps you to do necessary feature development only ones and use it wherever you want.