File-Scoped Namespaces in C#

File-scoped namespaces are a feature introduced in C# 10 that streamline namespace declaration, making code less nested and more readable by applying the namespace declaration to the entire file. This article explores how to use file-scoped namespaces and compares them with traditional block-scoped namespaces.

File Scoped Namespaces by Default

In C# 10 and later, you can use file-scoped namespaces by default. This means that when a namespace is declared at the top of a file, it applies to all the code within that file without needing braces to denote the scope.

namespace MyProject.Models;
public class User
{
    public string Name { get; set; }
}

C# Namespace Block Scoped vs File-Scoped

Traditionally, C# used block-scoped namespaces, which required braces and added an extra level of nesting to the code:

namespace MyProject.Models
{
    public class User
    {
        public string Name { get; set; }
    }
}

With file-scoped namespaces, the braces are omitted, reducing the nesting and making the file structure cleaner:

namespace MyProject.Models;
public class User
{
    public string Name { get; set; }
}

File Scoped Namespaces C# Version

File-scoped namespaces were introduced in C# 10 as part of .NET 6. This feature is supported in all project types that can use C# 10 or later.

C# File-Scoped Namespace EditorConfig

To enforce file-scoped namespaces in a project, you can configure this setting in the .editorconfig file:

# File-scoped namespace suggestion
dotnet_style_namespace_match_folder = true
csharp_style_namespace_declarations = file_scoped:suggestion

This configuration makes it a suggestion to use file-scoped namespaces, aligning namespace declarations with folder structures.

Enable File-Scoped Namespaces

To enable file-scoped namespaces across a project, ensure you are using C# 10 or later. You can set the C# version in your project file:

<PropertyGroup>
    <LangVersion>10.0</LangVersion>
</PropertyGroup>

C# File-Scoped Namespace Visual Studio

In Visual Studio, file-scoped namespaces are recognized automatically if you are using C# 10 or later. When you format the document (Edit > Advanced > Format Document or Ctrl+K, Ctrl+D), Visual Studio will maintain the file-scoped namespace format if it's already applied.

By adopting file-scoped namespaces, developers can reduce the complexity of their codebases, making them easier to read and maintain. This modern feature is particularly useful in projects with many small files, each containing a single class or interface, by reducing the amount of boilerplate code and increasing the overall elegance of the code structure.

File-scoped namespaces in c#