namespace:
System.Runtime.CompilerServices; It's primarily for compiler writer?
The coming called method should be declared under [MethodImplAttribute(MethodImplOptions.InternalCall, MehtodCodeType=MethodCodeType.Runtime)]
which means the method was implemented during the runtime.
MethodImplAttribute, a kind of Class. Specifies the details of how a method is implemented. And which cannot be inherited.
The object of component can be delcared in the method of App. But the method of the object should be
declared before the method being called. This will tell the RCW to provide a RVA.