Avoid excessive parameters on generic types
TypeName |
AvoidExcessiveParametersOnGenericTypes |
CheckId |
CA1005 |
Category |
Microsoft.Design |
Breaking Change |
Breaking |
Cause
An externally visible generic type has more than two type parameters.
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 there are more than two type parameters, 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 Exclude Warnings
Do not exclude 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.
Example
The following example shows a class that defines three generic type parameters which violates the rule.
Related Rules
Collections should implement generic interface
Do not declare static members on generic types
Do not nest generic types in member signatures
Generic methods should provide type parameter
Use generic event handler instances
Use generics where appropriate