Compile Time Style Enforcement

Enforce code style rules at compile time so the project fails to build if violations exist.

Supported Rules

Rule	Description
No var	Use explicit types instead of var
No unused usings	Remove unnecessary using directives
Collection expressions	Use simplified collection syntax like List<string> names = []
CancellationToken forwarding	Forward CancellationToken to methods that accept it

Configuration

EditorConfig

Create .editorconfig in the solution or project root:

root = true

[*.cs]
# Use explicit types instead of var (IDE0008)
csharp_style_var_for_built_in_types = false:error
csharp_style_var_when_type_is_apparent = false:error
csharp_style_var_elsewhere = false:error
dotnet_diagnostic.IDE0008.severity = error

# Remove unnecessary usings (IDE0005)
dotnet_diagnostic.IDE0005.severity = error

# Use collection expressions (IDE0028, IDE0300, IDE0305)
dotnet_style_collection_initializer = true:error
dotnet_style_prefer_collection_expression = true:error
dotnet_diagnostic.IDE0028.severity = error
dotnet_diagnostic.IDE0300.severity = error
dotnet_diagnostic.IDE0305.severity = error

# Forward CancellationToken to methods (CA2016)
dotnet_diagnostic.CA2016.severity = error

Project File

Add these properties to your .csproj:

<PropertyGroup>
  <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
  <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
  <NoWarn>$(NoWarn);1591</NoWarn>
</PropertyGroup>

Property Reference

Property	Purpose
TreatWarningsAsErrors	Fails build on any warning
EnforceCodeStyleInBuild	Enables IDE rules (IDE0005, IDE0008, etc.) during build
GenerateDocumentationFile	Required for IDE0005 (unused usings) to work
NoWarn=1591	Suppresses “missing XML comment” warnings from doc generation

Auto-fix Violations

Use dotnet format to automatically fix violations:

# Fix all style issues
dotnet format

# Fix a specific rule
dotnet format --diagnostics IDE0008 --severity error

Rule Details

IDE0008 - Use explicit type

// Bad
var name = "Michael";
var count = 42;

// Good
string name = "Michael";
int count = 42;

IDE0005 - Remove unnecessary usings

Removes using directives that are not referenced in the file.

IDE0028/IDE0300/IDE0305 - Collection expressions

// Bad
List<string> names = new List<string>();
List<int> numbers = new List<int> { 1, 2, 3 };

// Good
List<string> names = [];
List<int> numbers = [1, 2, 3];

CA2016 - Forward CancellationToken

// Bad - cancellationToken exists but not forwarded
async Task DoWorkAsync(CancellationToken cancellationToken)
{
    await client.SendAsync(request);
}

// Good
async Task DoWorkAsync(CancellationToken cancellationToken)
{
    await client.SendAsync(request, cancellationToken);
}