Dave's Notebook

Assign Multiple enum Values To One Variable

I saw this question and immediately thought, “You can’t! An Enum is an Integer that has been restricted to the values it can accept.”

And I was basically right. But, I forgot that even with an integer you can do the following in CSharp:

image

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int i = 1 | 2;

And in VB.NET

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Dim i As Integer = 1 Or 2

To end up with a variable i equal to 3 because both do bitwise ands.

So if I had an enumerated value

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enum F {
thing1 = 1,
thing2 = 2,
thing3 = 4
}

Or, in VB.NET

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Enum F
thing1 = 1
thing2 = 2
thing3 = 4
End Enum
``

You could then do the following in CSharp:

``` csharp
F fvar;

fvar = F.thing1 | F.thing2;

Or you could do it in VB.NET like this:

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Dim fvar As F = F.thing1 Or F.thing2

There’s just one small problem with doing all of this.

If you evaluate fvar, you see that it is equal to 3 because we did not define 3 to be a specific value in our enumeration. However, by adding the Flags attribute to our enum definition:

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[Flags]enum F {
thing1 = 1,
thing2 = 2,
thing3 = 4
}

Or

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<Flags()> _Enum F
thing1 = 1
thing2 = 2
thing3 = 4
End Enum

fvar will evaluate to:

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thing1 | thing2

in CSharp and in VB.NET…

Well, in VB.NET it still evaluates to 3.