Many predefined classes are grouped into categories of related classes called namespaces. Together, these namespaces are referred to as the .NET Framework Class Library.
Throughout the text,
using directives allow us to use library classes from the Framework Class Library without specifying their fully qualified names. For example, an app includes the declaration
in order to use the class names from the
System namespace without fully qualifying their names. This allows you to use the unqualified class name
Console, rather than the fully qualified class name
System.Console, in your code. A strength of C# is the large number of classes in the namespaces of the .NET Framework Class Library. Some ...