Code inspection: Annotation duplicate in hierarchy

This inspection reports a nullability annotation that repeats the same contract already inherited from a base member or implemented member.

This usually happens when an override or implementation adds [NotNull], [CanBeNull], or a similar annotation even though the base declaration already defines that nullability. The extra attribute does not add new information and can make the hierarchy noisier.

Example

                using JetBrains.Annotations;
                public class Base
                {
                    [NotNull]
                    public virtual object CreateValue() => new object();
                }
                public class Derived : Base
                {
                    [NotNull]
                    public override object CreateValue() => new object();
                }
            

                using JetBrains.Annotations;
                public class Base
                {
                    [NotNull]
                    public virtual object CreateValue() => new object();
                }
                public class Derived : Base
                {
                    public override object CreateValue() => new object();
                }
            

Quick-fix

A quick-fix helps you remove the redundant attribute from the derived declaration.

27 March 2026