CA2217: Do not mark enums with FlagsAttribute

 

For the latest documentation on Visual Studio 2017, see Visual Studio 2017 Documentation.

For the latest documentation on Visual Studio 2017, see CA2217: Do not mark enums with FlagsAttribute on docs.microsoft.com.

TypeNameDoNotMarkEnumsWithFlags
CheckIdCA2217
CategoryMicrosoft.Usage
Breaking ChangeNon Breaking

An externally visible enumeration is marked with FlagsAttribute and it has one or more values that are not powers of two or a combination of the other defined values on the enumeration.

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 suppress 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 Samples
{    
    // Violates this rule    
    [FlagsAttribute]        
    public enum Color
    { 
        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.

using System;

namespace Samples
{    
    [FlagsAttribute]    
    public enum Days    
    {        
        None        = 0,        
        Monday      = 1,        
        Tuesday     = 2,        
        Wednesday   = 4,        
        Thursday    = 8,        
        Friday      = 16,        
        All         = Monday| Tuesday | Wednesday | Thursday | Friday    
    }
}

CA1027: Mark enums with FlagsAttribute

System.FlagsAttribute

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