DLL(Dynamic linking library):
Definition:
A dll is linked to your program at run time.
what:a library linked to your program.
when:at run time.-->dynamic.
Apply:---->use the unqualified class names
Using Fully Qualified Names:Namespaces and types have unique names,which are described by fully qualified names that indicate a logical hierarchy.
using directive at the beginning of the file.--->allow you to use the unqualified class names to reference the DLL methods at compile time.