CA1813: Avoid unsealed attributes

Rule ID CA1813
Category Performance
Fix is breaking or non-breaking Breaking


A public type inherits from System.Attribute, is not abstract, and is not sealed (NotInheritable in Visual Basic).

Rule description

.NET provides methods for retrieving custom attributes. By default, these methods search the attribute inheritance hierarchy. For example, System.Attribute.GetCustomAttribute searches for the specified attribute type or any attribute type that extends the specified attribute type. Sealing the attribute eliminates the search through the inheritance hierarchy, and can improve performance.

How to fix violations

To fix a violation of this rule, seal the attribute type or make it abstract.

When to suppress warnings

It is safe to suppress a warning from this rule. Suppress only if you are defining an attribute hierarchy and cannot seal the attribute or make it abstract.


The following example shows a custom attribute that satisfies this rule.

// Satisfies rule: AvoidUnsealedAttributes.
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
public sealed class DeveloperAttribute : Attribute
    private string nameValue;
    public DeveloperAttribute(string name)
        nameValue = name;

    public string Name
            return nameValue;
Imports System

Namespace ca1813

    ' Satisfies rule: AvoidUnsealedAttributes.
    <AttributeUsage(AttributeTargets.Class Or AttributeTargets.Struct)>
    Public NotInheritable Class DeveloperAttribute
        Inherits Attribute

        Public Sub New(name As String)
            Me.Name = name
        End Sub

        Public ReadOnly Property Name() As String
    End Class

End Namespace

See also