editorconfig rule to enforce that namespace is set in all C# files

Question

I want to set a rule in .editorconfig so that all C# files where namespace is not explicitly set should render an error.

I've added these:

dotnet_diagnostic.IDE0130.severity = error # Namespace does not match folder structure
dotnet_diagnostic.IDE0161.severity = error # Namespace declaration preferences (prefer file-scoped)
csharp_style_namespace_declarations = file_scoped:error

Namespace is validated to follow file structure.

And to be file scoped

But if I remove the namespace altogether, I get no validation error.

Out of interest, why would you want to prevent file-scoped namespaces? That does explicitly set a namespace, so what do you object to about it? (Personally I love getting rid of completely unnecessary level of indentation...) — Jon Skeet
– Jon Skeet, Commented 20 hours ago
Not sure I understand, here is what I want to achieve: 1. All C# should have a namspace set explicitly (i.e. not possible to have a C# file missing namespace declaration) 2. All namespace declarations should be file scoped 3. All namespaces should match file structure With the current setup I solve 2 and 3, but not 1. — Max
– Max, Commented 19 hours ago
I think I'd misinterpreted the option - ignore me. (As for a solution to the actual problem - I'm not sure there's anything in editorconfig for this, but you could write your own Roslyn analyzer easily enough, or just a unit test which you could reuse across assemblies.) — Jon Skeet
– Jon Skeet, Commented 19 hours ago
Ok, it's for a client I'm working for and if I'd do that I'd need to justify the extra setup needed to achieve this "nice to have". So should there be no built-in way to do this check, I'll probably skip it. — Max
– Max, Commented 18 hours ago

Max · Accepted Answer · 2025-11-21 14:55:10Z

0

Based on the comment from Jon Skeet that this probably is not possible with editorconfig, I wrote a generic unit test for it.

using System.Text.RegularExpressions;
using Shouldly;

namespace Base.SharedTests.UnitTests;

public partial class CodeTests
{
    [Fact]
    public void AllFiles_WithCsExtension_ShouldHaveFileScopedNamespaces()
    {
        var solutionBasePath = Path.GetFullPath(
            Path.Combine(AppContext.BaseDirectory, "..", "..", "..", "..", "..")
        );

        var files = Directory
            .GetFiles(solutionBasePath, "*.cs", SearchOption.AllDirectories)
            .Where(f => !f.EndsWith("GlobalUsings.cs", StringComparison.Ordinal))
            .Where(f => !f.EndsWith("Program.cs", StringComparison.Ordinal))
            .Where(f => !f.Contains("/bin/", StringComparison.Ordinal))
            .Where(f => !f.Contains("/obj/", StringComparison.Ordinal));

        List<(string FileName, bool Result)> results =
        [
            .. files.Select(f =>
            {
                var text = File.ReadAllText(f);
                var fileName = Path.GetFileName(f);
                var result = NamespaceRegex().IsMatch(text);

                return (fileName, result);
            }),
        ];

        results.ShouldAllBe(r => r.Result == true);
    }

    [GeneratedRegex(@"^\s*namespace\s+[A-Za-z0-9_.]+\s*;", RegexOptions.Multiline)]
    private static partial Regex NamespaceRegex();
}

answered 17 hours ago

Max

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1 Comment

Jon Skeet 15 hours ago

I wouldn't check the files - I'd check the types in the assembly. That way you don't have to find the source files, or parse any C# code. You may need to exclude any "extra" types generated by the compiler though - they may have <> in the name, but you could see if you tried it...

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