Abstract [ Documentation]

Roslyn Analyzers inspect C#/VB code for style, quality, maintainability, design, and other issues. They are made up of code analysis rules. These rules work together with Visual Studio.

Code analysis rules consist of:

• Code style analysis rules
  • Diagnostic ID prefix `IDExxxx
  • Built into Visual Studio and (since .NET 5) the .NET SDK
  • Configured in text editor options or EditorConfig file
• Code quality analysis rules
  • Diagnostic ID prefix CAxxxx
  • Included (since .NET 5) in .NET SDK
• External analyzers — StyleCop, Roslynator, XUnit Analyzers, Sonar Analyzer, etc

Configuration [ Documentation]

Code analysis rules can be configured.

Severity

Each code analysis rule (both code quality and code style) has a severity level:

Hidden (silent) means Visual Studio will still show a code fix if available. None (none) means Visual Studio will never show a code fix.

Severity can be configured via an EditorConfig file where it takes precedence over rule sets (deprecated) and Solution Explorer.

Severity Scope

For a single analyzer rule:

• dotnet_diagnostic.RULE_ID.severity=SEVERITY

Note: IDE code-style analyzer rules use a different syntax: dotnet_style_NAME_OF_RULE=OPTION:SEVERITY

For a category of analyzer rules:

• dotnet_analyzer_diagnostic.category-RULE_CATEGORY.severity=SEVERITY
• See here for all categories.

For all analyzer rules:

• dotnet_analyzer_diagnostic.severity=SEVERITY

For multiple analyzer rules, precedence is Individual rule by ID > Category > All analyzer rules.

Analysis Mode

Each project has an analysis mode. This mode determines the set of analysis rules that are enabled. It is configured with the <AnalysisMode> MSConfig property:

In .NET 6+, you can enable a category of rules via the <AnalysisModeCATEGORY> MSBuild property. See here for more information.

In .NET 6+, Analysis Mode can be replaced with Analysis Level. This is configured differently. See here for more information.

Note: AnalysisMode and AnalysisLevel take precedence over any configuration in .editorconfig.

Excluding Generated Code

Automatically generated code files, like designer-generated files, can be excluded from code analysis.

Documentation: https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/configuration-options#exclude-generated-code

Configuration Files [ Documentation]

Code analysis rule configurations are stored in one of two configuration files:

1. EditorConfig files (file or folder-based configuration options)
2. Global AnalyzerConfig file (project-level configuration)

EditorConfig

EditorConfig files apply to specific source files or folders. This example applies to all .cs files in the current folder, including subfolders:

[*.cs] # The section header determines what files these rules apply to
<option_name> = <option_value>

See notes on EditorConfig.

AnalyzerConfig [ Documentation]

Suppressing Warnings

Code analyzer warnings can be suppressed in several ways.

Documentation: https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/suppress-warnings

Code Quality Rules (CAxxxx)

These rules inspect code for security, performance, design and other issues.

[See here] for a full list of rules( https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/#index-of-rules).

Options

Code quality rules have options that can be configured besides severity.
See here for a list of options.

To configure an option for all rules:

• dotnet_code_quality.OPTION_NAME=OPTION_VALUE

To configure an option for a category of rules:

• dotnet_code-quality.RULE_CATEGORY.OPTION_NAME=OPTION_VALUE

Code Style Rules (IDExxx)

Code style rules consist of language rules, formatting rules, and naming rules. These rules enable a consistent code style across a codebase. They can be defined in EditorConfig or in Visual Studio via Options > Text Editor > C# > Code Style > General.

[See here] for a full list of rules( https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/#index).

Preventing Rule Updates

By default, code analysis rules are updated as you upgrade to newer versions of the .NET SDK. This behavior can be suppressed.

Documentation: https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/overview?tabs=net-7#latest-updates