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Static enum in C#

Posted on 2009-05-13
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Last Modified: 2013-12-17
Hello,
I need to create some sort of static enumeration, but it's not allowed in C#, e.g. if I try the following:

static public enum  myEnum{ Option1 = 1, Option2, Option3 };

it will error out. I need to have it static as I do my calculations in different classes that interact with each other and one piece of a data is an array (i.e. int[] arOptions ). So when I use this array, I don't want to do this:

arOptions[ 3 ] = ...

as if I later decide to change meaning of #3, it will be a nightmare to change all references, instead, I want to do

arOptions[ Option3 ] = ...

And the only way to use enums now is to define the same enum in each class, but that's not good programming either.

So, how can and can I employ strong typing in my case?

Thanks
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Question by:Yurich
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5 Comments
 
LVL 6

Expert Comment

by:ViceroyFizzlebottom
ID: 24379726
You can define the Enum in it's own file under a specific namespace. Then for every file which references it, you can simply include a #using <whatever> to get access. It will also allow you to only change the specific values in only one place.
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LVL 6

Assisted Solution

by:ViceroyFizzlebottom
ViceroyFizzlebottom earned 100 total points
ID: 24379738
Also, you can define a static instance of your enum, so you could say:

public static myEnum mine = myEnum.Option3;
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LVL 9

Accepted Solution

by:
tculler earned 400 total points
ID: 24380585
Enumerations ("enums") are just sets of named constants, and constants are ALWAYS static in C#. The access modifier is all that should concern you. In other words, you cannot declare an enumeration as static--it is static implicitly, just like an instance modified with the keyword "const".

Accessing an enumeration is just like accessing the static members of a type. Just put the name of the enumeration, followed by the enumeration's member you wish to access. If you put an enumeration declaration within a class, you must specify the class, too. For example, to access the enumeration SomeEnum provided below...

// File: NestedEnum.cs (or whatever)
namespace SomeNamespace
{
     public class SomeClass
     {
          public enum SomeEnum { One, Two, Three, Four /*Etc*/ };
           // SomeClass members and such
     }
}

// File: EnumAccess_Main.cs (or whatever)
namespace SomeOtherNamespace
{
     public class Startup
     {
          public static void main()
          {
               SomeMethodThatNeedsSomeEnum(SomeNamespace.SomeClass.SomeEnum.One);
               // or, if you put "using SomeNamespace;" at the very top of the file, you can just say:
               SomeMethodThatNeedsSomeEnum(SomeClass.SomeEnum.One);
          }
     }
}

This is one way. However, it's easier to put the enum definition in the namespace and not within a class. See below.

// File: NestedEnum.cs (or whatever)
namespace SomeNamespace
{          
     public enum SomeEnum { One, Two, Three, Four /*Etc*/ };
     public class SomeClass
     {
           // SomeClass members and such
     }
}

// File: EnumAccess_Main.cs (or whatever)
namespace SomeOtherNamespace
{
     public class Startup
     {
          public static void main()
          {
               SomeMethodThatNeedsSomeEnum(SomeNamespace.SomeEnum.One);
               // or, if you put "using SomeNamespace;" at the very top of the file, you can just say:
               SomeMethodThatNeedsSomeEnum(SomeEnum.One);
          }
     }
}

Hope I helped,
Nate
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LVL 9

Expert Comment

by:tculler
ID: 24380599
Oh, one more thing. Remember that your enumeration will start numbering from your first specified value. If you make your first value = 1, choosing the "third" member will access the forth element of the array (aka, index 3, but "slot" 4). Was this intentional?
0
 
LVL 21

Author Comment

by:Yurich
ID: 24380950
2 Nate,
Very elaborated answer, thanks a lot. Dropping a static keyword worked as suggested. Using value = 1 was intentional as 0-slot was used for maintenance and in my case counting from 1 was easier than from 0.

Thanks a lot,
Yurich
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