CA1047: Do not declare protected members in sealed types

TypeName

DoNotDeclareProtectedMembersInSealedTypes

CheckId

CA1047

Category

Microsoft.Design

Breaking Change

Non-breaking

Cause

A public type is sealed (NotInheritable in Visual basic) and declares a protected member or a protected nested type. This rule does not report violations for Finalize methods, which must follow this pattern.

Rule Description

Types declare protected members so that inheriting types can access or override the member. By definition, you cannot inherit from a sealed type, which means that protected methods on sealed types cannot be called.

The C# compiler issues a warning for this error.

How to Fix Violations

To fix a violation of this rule, change the access level of the member to private, or make the type inheritable.

When to Suppress Warnings

Do not suppress a warning from this rule. Leaving the type in its current state can cause maintenance issues and does not provide any benefits.

Example

The following example shows a type that violates this rule.

Imports System

Namespace DesignLibrary

   Public NotInheritable Class BadSealedType
      Protected   Sub MyMethod
      End Sub 
   End Class 

End Namespace
using System;

namespace DesignLibrary
{
   public sealed class SealedClass
   {
      protected void ProtectedMethod(){}
   }
}