Learn the basics of C# from applications to signatures. Excerpt: An assembly that has an entry point is called an application. When an application runs, a new application domain is created. Several different instantiations of an application may exist on the same machine at the same time, and each has its own application domain. An application domain enables application isolation by acting as a container for application state. An application domain acts as a container and boundary for the types defined in the application and the class libraries it uses. Types loaded into one application domain are distinct from the same type loaded into another application domain, and instances of objects are not directly shared between application domains. For instance, each application domain has its own copy of static variables for these types, and a static constructor for a type runs at most once per application domain. Implementations are free to provide implementation-specific policy or mechanisms for creating and destroying application domains. Application startup occurs when the execution environment calls a designated method, which is the application’s entry point. This entry point method is always named Main, and it can have one of the following signatures.