Using Namespaces and References

What is a Namespace?

A namespace is a container that organizes classes and other types, preventing naming conflicts. It's similar to a folder structure in code.

namespace MyApp.Utilities
{
    public class MathHelper
    {
        public static int Square(int x) => x * x;
    }
}

To use it in another file:

using MyApp.Utilities;

Console.WriteLine(MathHelper.Square(5));

Common .NET Namespaces

• System – Base types (string, int, Console)
• System.IO – File and stream operations
• System.Collections.Generic – Lists, dictionaries
• System.Linq – LINQ extensions
• System.Threading.Tasks – Asynchronous programming

Adding Project References

If you split your app into multiple projects, you can reference one from another:

1. Right-click on the consuming project → Add → Project Reference
2. Select the target project (e.g., a class library)
3. Use using NamespaceName; to access its types

CLI Alternative:

dotnet add MyApp.ConsoleApp reference ../MyApp.Library/MyApp.Library.csproj

Organizing with Namespaces

Use meaningful, hierarchical namespace names based on project and folder structure:

• MyApp.Models
• MyApp.Services
• MyApp.Data

Visual Studio automatically aligns namespaces with folder names (unless manually overridden).

Namespaces and references keep your code modular and scalable. Next, we'll explore how to define and use custom classes within console applications for better structure and reusability.