The System.Web.Hosting namespace is not used in ASP.NET web applications; instead, it provides support for hosting the ASP.NET service outside of Internet Information Services (IIS) in a custom hosting application (which you would write using .NET). The two important classes in this namespace are ApplicationHost and SimpleWorkerRequest. The other classes provide lower-level framework support, and are not used directly in an application. Figure 26-1 shows the types in this namespace.