Export (0) Print
Expand All
Expand Minimize

Do not mark enums with FlagsAttribute

TypeName

DoNotMarkEnumsWithFlags

CheckId

CA2217

Category

Microsoft.Usage

Breaking Change

NonBreaking

The values of an enumeration are not powers of two, or combinations of powers of two defined by the enumeration, and the System.FlagsAttribute attribute is present.

An enumeration should have FlagsAttribute present only if each value defined in the enumeration is a power of two, or a combination of defined values.

To fix a violation of this rule, remove FlagsAttribute from the enumeration.

Do not exclude a warning from this rule.

The following example shows an enumeration, Color, that contains the value 3, which is neither a power of two, nor a combination of any of the defined values. The Color enumeration should not be marked with the FlagsAttribute.

using System;

namespace UsageLibrary
{
   // The following enumeration correctly applies the attribute.
   [FlagsAttribute]
   public enum DaysEnumNeedsFlags
   {
      None        = 0,
      Monday      = 1,
      Tuesday     = 2,
      Wednesday   = 4,
      Thursday    = 8,
      Friday      = 16,
      All         = Monday| Tuesday | Wednesday | Thursday | Friday
   }
   // Violates rule: DoNotMarkEnumsWithFlags.
   [FlagsAttribute]
   public enum ColorEnumShouldNotHaveFlags
   {
      None        = 0,
      Red         = 1,
      Orange      = 3,
      Yellow      = 4
   }
}

The following example shows an enumeration, Days, that meets the requirements for being marked with the System.FlagsAttribute.

Community Additions

ADD
Show:
© 2014 Microsoft