CA1505: Avoid unmaintainable code

Стаття
04/22/2023

Property	Value
Rule ID	CA1505
Title	Avoid unmaintainable code
Category	Maintainability
Fix is breaking or non-breaking	Non-breaking
Default threshold	10
Enabled by default in .NET 9	No

Cause

A type, method, field, property, or event has a low maintainability index value.

Rule description

The rule reports a violation when the maintainability index of a type, method, field, property, or event is less than 10. However, you can configure the threshold.

The maintainability index is calculated by using the following metrics: lines of code, program volume, and cyclomatic complexity. (Program volume is a measure of the difficulty of understanding of a type or method that's based on the number of operators and operands in the code. Cyclomatic complexity is a measure of the structural complexity of the type or method. You can learn more about code metrics at Measure complexity and maintainability of managed code.

A low maintainability index indicates that a type or method is probably difficult to maintain and would be a good candidate to redesign.

How to fix violations

To fix this violation, redesign the type or method and try to split it into smaller and more focused types or methods.

When to suppress warnings

You can suppress this warning when the type or method cannot be split or is considered maintainable despite its large size.

Note

You might see false positive warnings from this rule if all of the following apply:

You're using Visual Studio 2022 version 17.5 or later with an older version of the .NET SDK, that is, .NET 6 or earlier.
You're using the analyzers from the .NET 6 SDK or an older version of the analyzer packages, such as Microsoft.CodeAnalysis.FxCopAnalyzers.

The false positives are due to a breaking change in the C# compiler. Consider using a newer analyzer that contains the fix for the false positive warnings. Upgrade to Microsoft.CodeAnalysis.NetAnalyzers version 7.0.0-preview1.22464.1 or newer or use the analyzers from the .NET 7 SDK.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable CA1505
// The code that's violating the rule is on this line.
#pragma warning restore CA1505

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.CA1505.severity = none

For more information, see How to suppress code analysis warnings.

Configure threshold

You can configure the threshold at which this rule fires and the kinds of symbols to analyze. The allowable symbol kinds are:

Assembly
Namespace
Type
Method
Field
Event
Property

Create a text file named CodeMetricsConfig.txt.
Add the desired threshold to the text file in the following format:
```
CA1505: 20
```
In this example, the rule is configured to fire when the maintainability index of a type, method, field, property, or event is less than 20.
```
CA1505(Method): 5
CA1505(Type): 15
```
In this example, the rule is configured to fire when the maintainability index of a method is less than 5 or the maintainability index of a type is less than 15. With this configuration file, the rule will continue to flag fields, properties, and events whose maintainability index is less than the default threshold (10).
In the project file, mark the build action of the configuration file as AdditionalFiles. For example:
```
<ItemGroup>
  <AdditionalFiles Include="CodeMetricsConfig.txt" />
</ItemGroup>
```

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