Assign Multiple Enum Values to One Variable

By: Dave Bush

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:

int i = 1 | 2;
And in VB.NET
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
enum F { thing1 = 1, thing2 = 2, thing3 = 4 }
Or, in VB.NET
Enum F thing1 = 1 thing2 = 2 thing3 = 4End Enum

You could then do the following in CSharp:
F fvar;
fvar = F.thing1 | F.thing2;

Or you could do it in VB.NET like this:
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:
[Flags]enum F { thing1 = 1, thing2 = 2, thing3 = 4 }
Or
_Enum F thing1 = 1 thing2 = 2 thing3 = 4End Enum
fvar will evaluate to:
thing1 | thing2
in CSharp and in VB.NET…
Well, in VB.NET it still evaluates to 3.

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Dave answers ASP.NET related questions at .NET Answers. You can subscribe to his RSS feed here. He also runs an ASP.NET Web Hosting company at My Win Hosting.

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Dave answers ASP.NET related questions at .NET Answers and runs a ASP.NET Web Hosting company at My Win Hosting.

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