CA1501: Avoid excessive inheritance


The new home for Visual Studio documentation is Visual Studio 2017 Documentation on

The latest version of this topic can be found at CA1501: Avoid excessive inheritance.

|Breaking Change|Breaking|

A type is more than four levels deep in its inheritance hierarchy.

Deeply nested type hierarchies can be difficult to follow, understand, and maintain. This rule limits analysis to hierarchies in the same module.

To fix a violation of this rule, derive the type from a base type that is less deep in the inheritance hierarchy or eliminate some of the intermediate base types.

It is safe to suppress a warning from this rule. However, the code might be more difficult to maintain. Note that, depending on the visibility of base types, resolving violations of this rule might create breaking changes. For example, removing public base types is a breaking change.

The following example shows a type that violates the rule.

Imports System

Namespace MaintainabilityLibrary

   Class BaseClass
   End Class

   Class FirstDerivedClass
      Inherits BaseClass
   End Class

   Class SecondDerivedClass
      Inherits FirstDerivedClass
   End Class

   Class ThirdDerivedClass
      Inherits SecondDerivedClass
   End Class

   Class FourthDerivedClass
      Inherits ThirdDerivedClass
   End Class

   ' This class violates the rule.
   Class FifthDerivedClass
      Inherits FourthDerivedClass
   End Class

End Namespace