Namespaces & Directives

Part of the Object Oriented Programming section of Coddy's C# journey — lesson 2 of 70.

Namespaces organize your code and prevent naming conflicts. They group related classes together like folders organize files.

Create a class inside a namespace

namespace MyApp.Models
{
    public class User
    {
        public string Name { get; set; }
        
        public User(string name)
        {
            Name = name;
        }
    }
}

Use a using directive to access classes from another namespace

using System;
using MyApp.Models;

class Program
{
    static void Main()
    {
        User user = new User("Alice");
        Console.WriteLine(user.Name);
    }
}

Output:

Alice

Without a using directive, you must use the fully qualified name

MyApp.Models.User user = new MyApp.Models.User("Bob");

The using directive allows you to reference types in a namespace without typing the full namespace path each time. System is a common namespace containing fundamental classes like Console.

Challenge

Medium

You have a User class in the MyApp.Models namespace. Add the correct using directive in Program.cs to use the User class without the fully qualified name.

Cheat sheet

Namespaces organize code and prevent naming conflicts by grouping related classes together.

Create a class inside a namespace:

namespace MyApp.Models
{
    public class User
    {
        public string Name { get; set; }
        
        public User(string name)
        {
            Name = name;
        }
    }
}

Use a using directive to access classes from another namespace:

using System;
using MyApp.Models;

class Program
{
    static void Main()
    {
        User user = new User("Alice");
        Console.WriteLine(user.Name);
    }
}

Without a using directive, use the fully qualified name:

MyApp.Models.User user = new MyApp.Models.User("Bob");

The System namespace contains fundamental classes like Console.

Try it yourself

using System;
// TODO: Add using directive for MyApp.Models

class Program
{
    static void Main()
    {
        string userName = Console.ReadLine();
        // TODO: Create a User object using userName
        // TODO: Print "User created: " followed by the user's Name
    }
}