CA1048: Do not declare virtual members in sealed types

Applies to: Visual Studio Visual Studio for Mac

Note

This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Item	Value
RuleId	CA1048
Category	Microsoft.Design
Breaking change	Breaking

Cause

A public type is sealed and declares a method that is both virtual (Overridable in Visual Basic) and not final. This rule does not report violations for delegate types, which must follow this pattern.

Note

This rule has been deprecated. For more information, see Deprecated rules.

Rule description

Types declare methods as virtual so that inheriting types can override the implementation of the virtual method. By definition, you cannot inherit from a sealed type, making a virtual method on a sealed type meaningless.

The Visual Basic and C# compilers do not allow types to violate this rule.

How to fix violations

To fix a violation of this rule, make the method non-virtual 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.