Avoid unsealed attributes

Cause

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 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.

Example

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

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

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;
            }
        }
    }

}

Related Rules

Define accessors for attribute arguments

Mark attributes with AttributeUsageAttribute

See Also

Reference

Attribute Usage Guidelines