Configuration options for code analysis

Code analysis rules have various configuration options. Some of these options are specified as key-value pairs in an analyzer configuration file using the syntax <option key> = <option value>. Other options, which configure code analysis as a whole, are available as properties in your project file.

The most common option you'll configure is a rule's severity. You can configure the severity level for any rule, including code quality rules and code style rules. For example, to enable a rule as a warning, add the following key-value pair to an analyzer configuration file:

dotnet_diagnostic.<rule ID>.severity = warning

You can also configure additional options to customize rule behavior:

  • Code quality rules have options to configure behavior, such as which method names a rule should apply to.
  • Code style rules have options to define style preferences, such as where new lines are desirable.
  • Third-party analyzer rules can define their own configuration options, with custom key names and value formats.

General options

These options apply to code analysis as a whole. They cannot be applied only to a specific rule.

For additional options, see Code analysis properties.

Enable code analysis

Code analysis is enabled by default for projects that target .NET 5 and later versions. If you have the .NET 5+ SDK but your project targets a different .NET implementation, you can manually enable code analysis by setting the EnableNETAnalyzers property in your project file to true.

<PropertyGroup>
  <EnableNETAnalyzers>true</EnableNETAnalyzers>
</PropertyGroup>

Analysis mode

While the .NET SDK includes all code analysis rules, only some of them are enabled by default. The analysis mode determines which, if any, set of rules is enabled. You can choose a more aggressive analysis mode where most or all rules are enabled, or a more conservative analysis mode where most or all rules are disabled and, you can then opt in to specific rules as needed. Set your analysis mode by adding the AnalysisMode property to your project file.

<PropertyGroup>
  <AnalysisMode>Recommended</AnalysisMode>
</PropertyGroup>

Exclude generated code

.NET code analyzer warnings aren't useful on generated code files, such as designer-generated files, which users can't edit to fix any violations. In most cases, code analyzers skip generated code files and don't report violations on these files.

By default, files with certain file extensions or auto-generated file headers are treated as generated code files. For example, a file name ending with .designer.cs or .generated.cs is considered generated code. This configuration option lets you specify additional naming patterns to be treated as generated code. You configure additional files and folders by adding a generated_code = true | false entry to your configuration file. For example, to treat all files whose name ends with .MyGenerated.cs as generated code, add the following entry:

[*.MyGenerated.cs]
generated_code = true

Rule-specific options

Rule-specific options can be applied to a single rule, a set of rules, or all rules. The rule-specific options include:

Severity level

The following table shows the different rule severities that you can configure for all analyzer rules, including code quality and code style rules.

Severity configuration value Build-time behavior
error Violations appear as build errors and cause builds to fail.
warning Violations appear as build warnings but do not cause builds to fail (unless you have an option set to treat warnings as errors).
suggestion Violations appear as build messages and as suggestions in the Visual Studio IDE.
silent Violations aren't visible to the user.
none Rule is suppressed completely.
default The default severity of the rule is used. The default severities for each .NET release are listed in the roslyn-analyzers repo. In that table, "Disabled" corresponds to none, "Hidden" corresponds to silent, and "Info" corresponds to suggestion.

Tip

For information about how rule severities surface in Visual Studio, see Severity levels.

Scope

  • Single rule

    To set the rule severity for a single rule, use the following syntax.

    dotnet_diagnostic.<rule ID>.severity = <severity value>
    
  • Category of rules

    To set the default rule severity for a category of rules, use the following syntax. However, this severity setting only affects rules in that category that are enabled by default.

    dotnet_analyzer_diagnostic.category-<rule category>.severity = <severity value>
    

    The different categories are listed and described at Rule categories. In addition, you can find the category for a specific rule on its reference page, for example, CA1000.

  • All rules

    To set the default rule severity for all analyzer rules, use the following syntax. However, this severity setting only affects rules that are enabled by default.

    dotnet_analyzer_diagnostic.severity = <severity value>
    

Important

When you configure the severity level for multiple rules with a single entry, either for a category of rules or for all rules, the severity only applies to rules that are enabled by default. To enable rules that are disabled by default, you must either:

  • Add an explicit dotnet_diagnostic.<rule ID>.severity = <severity> configuration entry for each rule.
  • In .NET 6+, enable a category of rules by setting <AnalysisMode<Category>> to All.
  • Enable all rules by setting <AnalysisMode> to All or by setting <AnalysisLevel> to latest-All.

Note

The prefix for setting severity for a single rule, dotnet_diagnostic, is slightly different than the prefix for configuring severity via category or for all rules, dotnet_analyzer_diagnostic.

Precedence

If you have multiple severity configuration entries that can be applied to the same rule ID, precedence is chosen in the following order:

  • An entry for an individual rule by ID takes precedence over an entry for a category.
  • An entry for a category takes precedence over an entry for all analyzer rules.

Consider the following example, where CA1822 has the category "Performance":

[*.cs]
dotnet_diagnostic.CA1822.severity = error
dotnet_analyzer_diagnostic.category-performance.severity = warning
dotnet_analyzer_diagnostic.severity = suggestion

In the preceding example, all three severity entries are applicable to CA1822. However, using the specified precedence rules, the first rule ID-based entry wins over the next entries. In this example, CA1822 will have an effective severity of error. All other rules within the "Performance" category will have a severity of warning.

For information about how inter-file precedence is decided, see the Precedence section of the Configuration files article.