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CA1052: Static holder types should be sealed

TypeName

StaticHolderTypesShouldBeSealed

CheckId

CA1052

Category

Microsoft.Design

Breaking Change

Breaking

A public or protected type contains only static members and is not declared with the sealed (C# Reference) (NotInheritable (Visual Basic)) modifier.

This rule assumes that a type that contains only static members is not designed to be inherited, because the type does not provide any functionality that can be overridden in a derived type. A type that is not meant to be inherited should be marked with the sealed modifier to prohibit its use as a base type.

To fix a violation of this rule, mark the type as sealed. If you are targeting .NET Framework 2.0 or earlier, a better approach is to mark the type as static. In this manner, you avoid having to declare a private constructor to prevent the class from being created.

Suppress a warning from this rule only if the type is designed to be inherited. The absence of the sealed modifier suggests that the type is useful as a base type.

The following example shows a type that violates the rule.

using System;

namespace DesignLibrary
{
    public class StaticMembers
    {
        static int someField;

        public static int SomeProperty
        {
            get
            {
                return someField;
            }
            set
            {
                someField = value;
            }
        }

        StaticMembers() {}

        public static void SomeMethod() {}
    }
}

The following example shows how to fix a violation of this rule by marking the type with the static modifier.

using System; 

namespace DesignLibrary
{    
    public static class StaticMembers    
    {        
        private static int someField;     

        public static int SomeProperty        
        {            
            get { return someField; }            
            set { someField = value; }        
        }                

        public static void SomeMethod()         
        {        
        }         

        public static event SomeDelegate SomeEvent;    
    }     

    public delegate void SomeDelegate();
}
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