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CA1005: Avoid excessive parameters on generic types

  • Article
Property Value
Rule ID CA1005
Title Avoid excessive parameters on generic types
Category Design
Fix is breaking or non-breaking Breaking
Enabled by default in .NET 8 No

Cause

An externally visible generic type has more than two type parameters.

By default, this rule only looks at externally visible types, but this is configurable.

Rule description

The more type parameters a generic type contains, the more difficult it is to know and remember what each type parameter represents. It is usually obvious with one type parameter, as in List<T>, and in certain cases with two type parameters, as in Dictionary<TKey, TValue>. If more than two type parameters exist, the difficulty becomes too great for most users (for example, TooManyTypeParameters<T, K, V> in C# or TooManyTypeParameters(Of T, K, V) in Visual Basic).

How to fix violations

To fix a violation of this rule, change the design to use no more than two type parameters.

When to suppress warnings

Do not suppress a warning from this rule unless the design absolutely requires more than two type parameters. Providing generics in a syntax that is easy to understand and use reduces the time that is required to learn and increases the adoption rate of new libraries.

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 CA1005
// The code that's violating the rule is on this line.
#pragma warning restore CA1005

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

[*.{cs,vb}]
dotnet_diagnostic.CA1005.severity = none

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

Configure code to analyze

Use the following option to configure which parts of your codebase to run this rule on.

You can configure this option for just this rule, for all rules it applies to, or for all rules in this category (Design) that it applies to. For more information, see Code quality rule configuration options.

Include specific API surfaces

You can configure which parts of your codebase to run this rule on, based on their accessibility. For example, to specify that the rule should run only against the non-public API surface, add the following key-value pair to an .editorconfig file in your project:

dotnet_code_quality.CAXXXX.api_surface = private, internal

CA1010: Collections should implement generic interface

CA1000: Do not declare static members on generic types

CA1002: Do not expose generic lists

CA1003: Use generic event handler instances

See also