CA2217: Do not mark enums with FlagsAttribute
TypeName |
DoNotMarkEnumsWithFlags |
CheckId |
CA2217 |
Category |
Microsoft.Usage |
Breaking Change |
Non Breaking |
Cause
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.
Rule Description
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.
How to Fix Violations
To fix a violation of this rule, remove FlagsAttribute from the enumeration.
When to Suppress Warnings
Do not suppress a warning from this rule.
Example
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.
Imports System
Namespace Samples
' Violates this rule
<FlagsAttribute()> _
Public Enum Color
None = 0
Red = 1
Orange = 3
Yellow = 4
End Enum
End Namespace
using System;
namespace Samples
{
// Violates this rule
[FlagsAttribute]
public enum Color
{
None = 0,
Red = 1,
Orange = 3,
Yellow = 4
}
}
using namespace System;
namespace Samples
{
// Violates this rule
[FlagsAttribute]
public enum class 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.
Imports System
Namespace Samples
<FlagsAttribute()> _
Public Enum Days
None = 0
Monday = 1
Tuesday = 2
Wednesday = 4
Thursday = 8
Friday = 16
All = Monday Or Tuesday Or Wednesday Or Thursday Or Friday
End Enum
End Namespace
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
}
}
using namespace System;
namespace Samples
{
[FlagsAttribute]
public enum class Days
{
None = 0,
Monday = 1,
Tuesday = 2,
Wednesday = 4,
Thursday = 8,
Friday = 16,
All = Monday| Tuesday | Wednesday | Thursday | Friday
};
}
Related Rules
CA1027: Mark enums with FlagsAttribute