#523 – The using Directive Allows Omitting Namespace

A typical C# program will use types that are defined in a variety of namespaces.  Specifying the fully qualified type name that includes the namespace can become tedious.

A using directive tells the compiler what namespaces to look for types in, avoiding the need for fully qualified type names.

Assume that we have a Dog type, defined in the DogLibrary namespace.  The fully qualified type name is DogLibrary.Dog.  But in the code fragment below, we can just use Dog as the type name, because of the using directive.

using DogLibrary;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            Dog kirby = new Dog();
            kirby.Bark();
        }
    }
}

So you can use a type name without its namespace if:

• The type is defined in the same namespace as the current code
• A using directive for the type’s namespace is present