Why is this an issue?
When you annotate an Enum with the Flags attribute, you must not rely on the values that are automatically
set by the language to the Enum members, but you should define the enumeration constants in powers of two (1, 2, 4, 8, and so on).
Automatic value initialization will set the first member to zero and increment the value by one for each subsequent member. As a result, you won’t be
able to use the enum members with bitwise operators.
Exceptions
The default initialization of 0, 1, 2, 3, 4, … matches 0, 1, 2, 4, 8 … in the first three values, so no issue is
reported if the first three members of the enumeration are not initialized.
How to fix it
Define enumeration constants in powers of two, that is, 1, 2, 4, 8, and so on.
Code examples
Noncompliant code example
<Flags()>
Enum FruitType ' Non-Compliant
None
Banana
Orange
Strawberry
End Enum
Module Module1
Sub Main()
Dim bananaAndStrawberry = FruitType.Banana Or FruitType.Strawberry
Console.WriteLine(bananaAndStrawberry.ToString()) ' Will display only "Strawberry"
End Sub
End Module
Compliant solution
<Flags()>
Enum FruitType ' Compliant
None = 0
Banana = 1
Orange = 2
Strawberry = 4
End Enum
Module Module1
Sub Main()
Dim bananaAndStrawberry = FruitType.Banana Or FruitType.Strawberry
Console.WriteLine(bananaAndStrawberry.ToString()) ' Will display "Banana, Strawberry"
End Sub
End Module
Resources
Documentation
