Code inspection: Class with virtual (overridable) members never inherited (non-private accessibility)
This inspection reports public classes that have one or more overridable members (virtual in C# or Overridable in Visual Basic), but have no inheritors in the solution.
On the one hand, making a member overridable indicates an intention to override it in a subclass, but on the other hand, there are no subclasses.
To resolve this contradiction, consider removing the virtual or Overridable modifiers. If the class is intentionally designed not to have any inheritors, you could add the sealed (NotInheritable in Visual Basic) modifier to the class.
For the solution-wide inspection to work, you need to enable at least one of the following:
Simplified global usage checking: select Show unused non-private type members when solution-wide analysis is off on the page of JetBrains Rider settings Ctrl+Alt+S.
Solution-wide analysis: select Enable solution-wide analysis on the page of JetBrains Rider settings Ctrl+Alt+S.
Note that even if the reported class has no direct usages in your solution, there could be cases where it is used indirectly — for example, via reflection — or it could just be designed as public API. In all those cases, you would want to suppress the usage-checking inspection for the class in one of the following ways:
The recommended way is to decorate the implicitly used class with a code annotation attribute. There are two attributes for this purpose: [UsedImplicitly] and [PublicAPI], which are functionally similar, but let you and your teammates understand how the class is actually used.
You can also suppress usage-checking inspections with any custom attribute. To do so, mark the definition of that attribute with the [MeansImplicitUse] attribute.
And finally, you can suppress a specific usage-checking inspection as any other code inspection with a suppression comment or a suppression attribute.