You can provide the common language runtime with configuration information for a new application domain using the AppDomainSetup interface. When creating your own application domains, the most important property is ApplicationBase. The other AppDomainSetup properties are used mainly by runtime hosts to configure a particular application domain. The ApplicationBase property defines the root directory of the application. When the runtime needs to satisfy a type request, it probes for the assembly containing the type in the directory specified by the ApplicationBase property.