problem regarding assigning numbers to an enum variable

Question

I've created a simple enum in C# as follows

enum Direction
{
    North,
    South,
    East,
    West
}

Now I'm creating a variable of this Direction enum as :

Direction D = (Direction)3;
Console.WriteLine(D.ToString());

Every thing goes fine and code works as expected and gives the following as output.

West

but now if I changes the code a bit like :

Direction D = (Direction)8;
Console.WriteLine(D.ToString());

it gives following as output :

So finally the questions came in my mind are:

Why this is getting done when the max acceptable value is 3.
If its getting accepted at time of compiling then why it's not throwing any exception while .net framework is such a robust framework yet.
And at last but not the least, if all is not going expected why it's giving output 8.

Thanks in advance buddies :)

GURU

Hey thanks to dtb for giving me such a wonderful answer but here I'd like to add a bit more I found somewhere on msdn. I can use the following code: Enum.IsDefined(typeof(Direction), 8) to check whether 8 is valid value of not before assigning it. :) — Pratik Purohit
– Pratik Purohit, Commented Sep 18, 2010 at 18:20

dtb · Accepted Answer · 2010-09-18 17:37:14Z

1

Why this is getting done when the max acceptable value is 3.

This assumption is not correct. You can assign any value that's within the range of the enum's base type (here: int) to a variable of that enum type.

If its getting accepted at time of compiling then why it's not throwing any exception while .net framework is such a robust framework yet.

It doesn't throw an exception, because it's not an exceptional situation, but perfectly valid.

And at last but not the least, if all is not going expected why it's giving output 8.

Because there is no enum member that gives a name to the value 8.

If you don't want a enum value other than those with a name to be passed to a method, you should check the method's inputs:

void Move(Direction d)
{
    if (d != Direction.North && d != Direction.South &&
        d != Direction.East  && d != Direction.West)
    {
        throw new ArgumentOutOfRangeException("d");
    }

    // ...
}

answered Sep 18, 2010 at 17:37

dtb

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to StackOverflow Over a year ago

... or even throw new InvalidEnumArgumentException("d", (int) d, typeof(Direction));

Community · Accepted Answer · 2017-05-23 11:55:22Z

1

Enums are just named constants and C# doesn't offer any range check if you cast a value to an enum.

1) There's no range check. Look at enums like a (usually) small set of names for a (usually) much larger set of numbers. I.e. C# lets you assign names to specific values, but it doesn't limit the allowable values, so an enum variable may take any value of the underlying type (default is int) if you cast it.

2) Same as 1) really

3) What else would you expect. You haven't assigned a name for that value.

You may want to check this question as well.

edited May 23, 2017 at 11:55

CommunityBot

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answered Sep 18, 2010 at 17:39

Brian Rasmussen

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Comments

NA Slacker · Accepted Answer · 2010-09-18 17:39:20Z

0

Normally when you declare an enum like that you set the values according to the list:

enum Direction{
North,
South,
East,
West}

Direction D = Direction.East;

What is your reasoning behind trying to set a value of 8?

answered Sep 18, 2010 at 17:39

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1 Comment

dtb Over a year ago

You can set it to a value of 8. OP asks why.

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