CA1405: COM visible type base types should be COM visible
For the latest documentation on Visual Studio 2017, see Visual Studio 2017 Documentation.
A Component Object Model (COM) visible type derives from a type that is not COM visible.
When a COM visible type adds members in a new version, it must abide by strict guidelines to avoid breaking COM clients that bind to the current version. A type that is invisible to COM presumes it does not have to follow these COM versioning rules when it adds new members. However, if a COM visible type derives from the COM invisible type and exposes a class interface of ClassInterfaceType.AutoDual or AutoDispatch (the default), all public members of the base type (unless they are specifically marked as COM invisible, which would be redundant) are exposed to COM. If the base type adds new members in a subsequent version, any COM clients that bind to the class interface of the derived type might break. COM visible types should derive only from COM visible types to reduce the chance of breaking COM clients.
To fix a violation of this rule, make the base types COM visible or the derived type COM invisible.
Do not suppress a warning from this rule.
The following example shows a type that violates the rule.
Imports System Imports System.Runtime.InteropServices <Assembly: ComVisibleAttribute(False)> Namespace InteroperabilityLibrary <ComVisibleAttribute(False)> _ Public Class BaseClass Sub SomeSub(valueOne As Integer) End Sub End Class ' This class violates the rule. <ComVisibleAttribute(True)> _ Public Class DerivedClass Inherits BaseClass Sub AnotherSub(valueOne As Integer, valueTwo As Integer) End Sub End Class End Namespace