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FxCop Warnings
 Avoid unsealed attributes

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This page is specific to
Microsoft Visual Studio 2005/.NET Framework 2.0

Other versions are also available for the following:
Visual Studio Team System
Avoid unsealed attributes

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).

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.

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

It is safe to exclude 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.

Visual Basic
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
        Get
            Return nameValue
        End Get
    End Property
End Class 

End Namespace
C#
using System;

namespace PerformanceLibrary 
{
    // 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
        {
            get 
            {
                return nameValue;
            }
        }
    }

}
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