Namespaces and Assemblies

C# in Visual Studio 2026 — a hands-on guide for developers at every level.

Namespaces

Namespaces organise code into logical groups and prevent name collisions. Every type in .NET lives inside a namespace.

namespace MyApp.Utilities
{
    public class MathHelper
    {
        public static int Double(int n) => n * 2;
    }
}

C# 10+ supports file-scoped namespaces which removes one level of indentation:

namespace MyApp.Utilities;  // no curly braces needed

public class MathHelper
{
    public static int Double(int n) => n * 2;
}

using Directives

using System.Collections.Generic;
using System.Linq;
using MyApp.Utilities;

var result = MathHelper.Double(21); // 42

Global usings (C# 10+)

Put global usings in a single file (e.g. GlobalUsings.cs) to apply them across the whole project:

global using System;
global using System.Collections.Generic;
global using System.Linq;

Assemblies and Projects

A compiled C# project produces an assembly — either a .dll (library) or an .exe (executable). A Solution (.sln) can contain multiple projects that reference each other.