C# using numbers in an enum

Question

This is a valid enum

public enum myEnum
{
  a= 1,
  b= 2,
  c= 3,
  d= 4,
  e= 5,
  f= 6,
  g= 7,
  h= 0xff
};

But this is not

public enum myEnum
{
  1a = 1,
  2a = 2,
  3a = 3,
};

Is there a way I can use an number in a enum? I already have code that would populate dropdowns from enums so it would be quite handy

Variable names cannot start with number. This being said it is not clear why do you need something like this so cannot provide helpful answer. — Darin Dimitrov, Oct 12 '10 at 16:32
Duplicate question... http://stackoverflow.com/questions/2952192/how-can-i-create-an-enum-using-numbers — Dan Puzey, Oct 12 '10 at 16:32

Kirk Woll · Accepted Answer · 2016-02-03T15:08:54.273

No identifier at all in C# may begin with a number (for lexical/parsing reasons). Consider adding a [Description] attribute to your enum values:

public enum myEnum
{
    [Description("1A")]
    OneA = 1,
    [Description("2A")]
    TwoA = 2,
    [Description("3A")]
    ThreeA = 3,
};

Then you can get the description from an enum value like this:

((DescriptionAttribute)Attribute.GetCustomAttribute(
    typeof(myEnum).GetFields(BindingFlags.Public | BindingFlags.Static)
        .Single(x => (myEnum)x.GetValue(null) == enumValue),    
    typeof(DescriptionAttribute))).Description

Based on XSA's comment below, I wanted to expand on how one could make this more readable. Most simply, you could just create a static (extension) method:

public static string GetDescription(this Enum value)
{
    return ((DescriptionAttribute)Attribute.GetCustomAttribute(
        value.GetType().GetFields(BindingFlags.Public | BindingFlags.Static)
            .Single(x => x.GetValue(null).Equals(value)),
        typeof(DescriptionAttribute)))?.Description ?? value.ToString();
}

It's up to you whether you want to make it an extension method, and in the implementation above, I've made it fallback to the enum's normal name if no [DescriptionAttribute] has been provided.

Now you can get the description for an enum value via:

myEnum.OneA.GetDescription()

Nice Solution; but is there an easier way to retreive the description shorter than these 4 lines ? — Xavier, Feb 03 '16 at 10:20
Should also point out that it's not limited to `Enum`s, you can use it for anything you apply the `DescriptionAttirbute` to. — will, Jun 23 '16 at 15:06

score 14 · Answer 2 · edited May 23 '17 at 12:18

14

No, there isn't. C# does not allow identifiers to start with a digit.

Application usability note: In your application you should not display code identifiers to the end-user anyway. Think of translating individual enumeration items into user-friendly displayable texts. Sooner or later you'll have to extend the enum with an item whose identifier won't be in a form displayable to the user.

UPDATE: Note that the way for attaching displayable texts to enumeration items is being discusses, for example, here.

edited May 23 '17 at 12:18

Community

1
1

answered Oct 12 '10 at 16:32

Ondrej Tucny

27,626
6
70
90

2

You can use DescriptionAttribute to associate a user-friendly string with each enum value and populate your dropdowns by extracting the attribute values instead of showing the raw enums. – John Bowen Oct 12 '10 at 16:45
I needed to define an enumeration for printer types that are 58MM and 80MM. These are user friendly displayable texts :P. Nevertheless, solved with _58mm – kuklei Mar 12 '21 at 16:58

score 10 · Answer 3 · answered Oct 12 '10 at 16:39

An identifier in C# (and most languages) cannot start with a digit.

If you can modify the code that populates a dropdown with the enumeration names, you could maybe have a hack that strips off a leading underscore when populating the dropdown and define your enum like so:

public enum myEnum
{
  _1a = 1,
  _2a = 2,
  _3a = 3
};

Or if you don't like the underscores you could come up with your own 'prefix-to-be-stripped' scheme (maybe pass the prefix to the constructor or method that will populate the dropdown from the enum).

Chandraprakash · Answer 4 · 2021-10-28T09:09:35.547

5

Short and crisp 4 line code.

We simply use enums as named integer for items in code,

so any simplest way is good to go.

public enum myEnum
{
    _1 = 1,
    _2,
    _3,
};

Also for decimal values,

public enum myEnum
{
    _1_5 = 1,
    _2_5,
    _3_5,
};

So while using this in code,

int i = cmb1.SelectedIndex(0); // not readable
int i = cmb1.SelectedIndex( (int) myEnum._1_5); // readable

edited Oct 28 '21 at 09:09

answered Oct 13 '20 at 19:18

Chandraprakash

773
1
10
18

Can you explain how `(int) myEnum._1_5` is more readable than `0`? And to start with, they're not equivalent in your code. It seems like it makes things hard to understand to me. – Enigmativity Jul 01 '21 at 22:37
1

_1_5 in a remote code can be understood as 1.5, but 0 cannot be understood as 1.5. Thats how – Chandraprakash Jul 03 '21 at 18:58
You're saying that you have a number, `1.5`, in an array at position `0`, so the most readable way to access the `1.5` is to do `array[(int)myEnum._1_5]`? That's crazy. If at compile-time you knew you needed `1.5` then `double value = 1.5;` is far better than `double value = array[(int)myEnum._1_5];`. Please tell me in what circumstance this increase in verbosity and indirection make sense? – Enigmativity Jul 04 '21 at 01:57
I have a dropdown which has border values for line in PowerPoint which has values like 1, 1.5, 3, 5 etc which I store in enum. So it's easy for me to get/set index based on these value – Chandraprakash Jul 15 '21 at 18:06
I think I'd have to see your code to understand why it's useful. – Enigmativity Jul 16 '21 at 01:29
In simple words, when you only have choice to select handful of values from dropdown, and here readable in the sense, 0 doesn't say anything, but _1_5 you can understand what value is choosen. – Chandraprakash Aug 07 '21 at 19:15
Again, I'd have to see actual code to hopefully understand why this is useful. – Enigmativity Aug 08 '21 at 00:48

score 4 · Answer 5 · answered Oct 12 '10 at 16:33

4

No way. A valid identifier (ie a valid enumeration member) cannot start with a digit.

answered Oct 12 '10 at 16:33

Noe

386
1
5

score 4 · Answer 6 · answered Oct 12 '10 at 16:34

Enumerations are no different than variables in terms of naming rules. Therefore, you can't start the name with a number. From this post, here are the main rules for variable naming.

The name can contain letters, digits, and the underscore character (_).
- The first character of the name must be a letter. The underscore is also a legal first character, but its use is not recommended at the beginning of a name. An underscore is often used with special commands, and it's sometimes hard to read.
- Case matters (that is, upper- and lowercase letters). C# is case-sensitive; thus, the names count and Count refer to two different variables.
- C# keywords can't be used as variable names. Recall that a keyword is a word that is part of the C# language. (A complete list of the C# keywords can be found in Appendix B, "C# Keywords.")

Better yet, the C# Language Specification section on Identifiers: http://msdn.microsoft.com/en-us/library/aa664670(v=VS.71).aspx — Jim Mischel, Oct 12 '10 at 16:37

score 4 · Answer 7 · answered Oct 12 '10 at 16:35

4

Identifiers can't start with numbers. However, they can contain numbers.

answered Oct 12 '10 at 16:35

Rohan Singh

20,497
1
41
48

score -3 · Answer 8 · edited Nov 25 '15 at 02:59

Here is what i came up with as an alternative, where I needed Enums to use in a "for" Loop and a string representation equivalent to use in a Linq query.

Create enums namespace to be used in "for" Loop.

public enum TrayLevelCodes
    {
        None,
        _5DGS,
        _5DG,
        _3DGS,
        _3DG,
        _AADC,
        _ADC,
        _MAAD,
        _MADC
    };

Create strings based on enum created to be used for Linq query

public string _5DGS = "\"5DGS\"",
        _5DG = "\"5DG\"",
        _3DGS = "\"3DGS\"",
        _3DG = "\"3DG\"",
        _AADC = "\"AADC\"",
        _ADC = "\"ADC\"",
        _MAAD = "\"MAAD\"",
        _MADC = "\"MADC\"";

Create function that will take an enum value as argument and return corresponding string for Linq query.

public string GetCntnrLvlDscptn(TrayLevelCodes enumCode)
        {
            string sCode = "";
            switch (enumCode)
            {
                case TrayLevelCodes._5DGS:
                    sCode = "\"5DGS\"";
                    break;
                case TrayLevelCodes._5DG:
                    sCode = "\"5DG\"";
                    break;
                case TrayLevelCodes._3DGS:
                    sCode = "\"3DGS\"";
                    break;
                case TrayLevelCodes._3DG:
                    sCode = "\"3DG\"";
                    break;
                case TrayLevelCodes._AADC:
                    sCode = "\"AADC\"";
                    break;
                case TrayLevelCodes._ADC:
                    sCode = "\"AAC\"";
                    break;
                case TrayLevelCodes._MAAD:
                    sCode = "\"MAAD\"";
                    break;
                case TrayLevelCodes._MADC:
                    sCode = "\"MADC\"";
                    break;
                default:
                    sCode = "";
                    break;
            }
                return sCode;
        }

Here is how i am using what i created above.

for (var trayLevelCode = TrayLevelCodes._5DGS; trayLevelCode <= TrayLevelCodes._MADC; trayLevelCode++)
{
    var TrayLvLst = (from i in pair1.Value.AutoMap
                     where (i.TrayLevelCode == HTMLINFO.GetCntnrLvlDscptn(trayLevelCode))
                     orderby i.TrayZip, i.GroupZip
                     group i by i.TrayZip into subTrayLvl
                     select subTrayLvl).ToList();
    foreach (DropShipRecord tray in TrayLvLst)
    {

    }
}

It'd be a lot easier to just use the `Description` attribute. — siride, Nov 25 '15 at 03:51

C# using numbers in an enum

8 Answers8

Linked

Related