EditorConfig control File-scoped namespace declaration

Question

I'm using C# 10 new feature File-scoped namespace declaration.

I have old code like this

namespace SampleCode
{
    public class MyClass
    {
    }
}

I'm moving this code to

namespace SampleCode;

public class MyClass
{
}

But I have a bunch of warnings : IDE0160: Convert to block scoped namespace

How do I make sure people will have warnings only with old syntax ?

Answer 1

To control the code style in editorconfig use this line :

To enforce this style

namespace SampleCode
{
    public class MyClass
    {
    }
}

Add this line in .editorconfig

# IDE0160: Convert to block-scoped namespace
csharp_style_namespace_declarations = block_scoped:warning

To enforce this style

namespace SampleCode;

public class MyClass
{
}

Add this line in .editorconfig

# IDE0160: Convert to file-scoped namespace
csharp_style_namespace_declarations = file_scoped:warning

Answer 2

Update 2022-01-27 (all scenarios setup)

JetBrains Rider does support the dotnet_diagnostic.IDE* syntax starting from version 2021.3.2.
This simplifies the setup for all possible scenarios into this:

EditorConfig

csharp_style_namespace_declarations = file_scoped:error
dotnet_diagnostic.IDE0161.severity = error

CSProj

<PropertyGroup>
  <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
</PropertyGroup>

This will cover all the scenarios. Original answer below. Still worth to read it.

---

There are several different settings which you should control based on your desired state, used IDEs and workflow.

They are described in this article which I strongly recommend to read before you start building .editorconfig for your project.

Here is a summary for File-scoped, Block-scoped usings, respectively.

EditorConfig/CSproj setup for File-scoped usings

---

Visual Studio (error on violation)

EditorConfig

csharp_style_namespace_declarations = file_scoped
dotnet_diagnostic.IDE0161.severity = error

Note

Syntax option = rule:severity will be deprecated, sooner or later.

---

JetBrains Rider (error on violation)

EditorConfig

csharp_style_namespace_declarations = file_scoped:error

Note

Rider doesn't support dotnet_diagnostic.IDE* syntax.

---

CLI build e.g., CI/CD pipeline

EditorConfig

csharp_style_namespace_declarations = file_scoped
dotnet_diagnostic.IDE0161.severity = error

CSProj

<PropertyGroup>
  <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
</PropertyGroup>

---

Recommended setup

EditorConfig

csharp_style_namespace_declarations = file_scoped:error
dotnet_diagnostic.IDE0161.severity = error

CSProj

<PropertyGroup>
  <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
</PropertyGroup>

Note

Is the current .NET EditorConfig syntax a mess? Definitely.

EditorConfig/CSproj setup for Block-scoped usings

---

Visual Studio (error on violation)

EditorConfig

csharp_style_namespace_declarations = block_scoped
dotnet_diagnostic.IDE0160.severity = error

Note

Syntax option = rule:severity will be deprecated, sooner or later.

---

JetBrains Rider (error on violation)

EditorConfig

csharp_style_namespace_declarations = block_scoped:error

Note

Rider doesn't support dotnet_diagnostic.IDE* syntax.

---

CLI build e.g., CI/CD pipeline

EditorConfig

csharp_style_namespace_declarations = block_scoped
dotnet_diagnostic.IDE0160.severity = error

---

CSProj

<PropertyGroup>
  <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
</PropertyGroup>

---

Recommended setup

EditorConfig

csharp_style_namespace_declarations = block_scoped:error
dotnet_diagnostic.IDE0160.severity = error

CSProj

<PropertyGroup>
  <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
</PropertyGroup>