A good online shopping cart behaves similarly to its model in the physical universe. As a shopper, you should be able to browse through the merchandise, choosing items to store in the virtual shopping cart, eliminating them easily and updating quantities. The Web site should do all the math, including taxes, and get a shipping address. The shopping cart should provide multiple ways to pay for the item, including credit card, PayPal, and possibly mailing in a check.

After you place the order, the site should send an e-mail message when the item ships, or to tell you about a problem. The message should include a tracking number for FedEx, UPS, or other shipper. If an item hasn't shipped, you should be able to cancel the order. When you return to a site, it should remember you and your previous purchases.

Site administrators have additional needs. Ultimately, an e-commerce site should require very little administration, so the business owner can focus on other duties. It should be easy to set up the shopping cart system, to choose the items offered for sale, and to upload their photos, descriptions, prices, and so on. The site needs to track inventory, reporting how many items are in stock. It also needs an interface for modifying the stock amounts, in case they get out of sync. The shopping cart system should handle common problems: if the stock runs out, perhaps the site should send you a notification. In that case, it definitely should not offer the product for sale, instead displaying a message of your choice.

You could write all this functionality yourself, but why bother? Instead, you can use existing libraries of ASP.NET code to create or customize an e-commerce Web site that accomplishes all of the tasks I listed above. In this article, I review three shopping cart kits for ASP.NET Web sites: the open source CommerceStarterKit, and two commercial applications, AspDotNetStorefront and DotNetCart.

I take a two-fold approach, examining both how a site performs as a standalone product for those who administer the site, and how the package can serve as a starting point for a web developer.