One of the following accessibility rules has been violated:
- The accessibility of the parent class (PUBLIC, PROTECTED, or PRIVATE) must be the same as, or greater than, the accessibility of the child class.
- The types used in the signature of any member must be as accessible as the member itself. For example, an argument type or return type cannot have private accessibility in a publicly accessible method.
- Accessibility cannot be changed on overridden virtual members. The accessibility of an overridden method or property must be the same as the virtual member it overrides in the parent class.