Why is this an issue?

There is no good excuse for an empty class. If it’s being used simply as a common extension point, it should be replaced with an interface. If it was stubbed in as a placeholder for future development it should be fleshed-out. In any other case, it should be eliminated.

Noncompliant code example

public class Empty // Noncompliant
{
}

Compliant solution

public interface IEmpty
{
}

Exceptions

• Partial classes are ignored entirely, as source generators often use them.
• Classes with names ending in Command, Message, Event, or Query are ignored as messaging libraries often use them.
• Subclasses of System.Exception are ignored; even an empty Exception class can provide helpful information by its type name alone.
• Subclasses of System.Attribute and classes annotated with attributes are ignored.
• Subclasses of generic classes are ignored, as they can be used for type specialization even when empty.
• Subclasses of certain framework types — like the PageModel class used in ASP.NET Core Razor Pages — are ignored.
• Subclass of a class with non-public default constructors are ignored, as they widen the constructor accessibility.

using Microsoft.AspNetCore.Mvc.RazorPages;

public class EmptyPageModel: PageModel // Compliant - an empty PageModel can be fully functional, the C# code can be in the cshtml file
{
}