CA1813: Avoid unsealed attributes


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TypeName AvoidUnsealedAttributes
CheckId CA1813
Category Microsoft.Performance
Breaking Change Breaking


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

Rule Description

The .NET Framework class library 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. You should do this 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.

using System;

namespace PerformanceLibrary 
    // Satisfies rule: AvoidUnsealedAttributes.

    public sealed class DeveloperAttribute: Attribute
        private string nameValue;
        public DeveloperAttribute(string name) 
            nameValue = name; 
        public string Name
                return nameValue;

Imports System

Namespace PerformanceLibrary

' Satisfies rule: AvoidUnsealedAttributes.
<AttributeUsage(AttributeTargets.Class Or AttributeTargets.Struct)>  _
NotInheritable Public Class DeveloperAttribute
    Inherits Attribute
    Private nameValue As String
    Public Sub New(name As String)
        nameValue = name
    End Sub
    Public ReadOnly Property Name() As String
            Return nameValue
        End Get
    End Property
End Class 

End Namespace

CA1019: Define accessors for attribute arguments

CA1018: Mark attributes with AttributeUsageAttribute

See Also