Enum Display Name - Use variable?

Question

Can I do this ? It doesn't seem so.

public enum Options
{
   [Display(Name = string.Format("{0} - {1}","Option One", MyClass.myVariable))]
   OptionOne=1,
   [Display(Name = string.Format("{0} - {1}","Option Two", MyClass.myVariable))]
   OptionTwo=2
}

As opposed to this

public enum Options
{
   [Display(Name = "Option 1")]
   OptionOne=1,
   [Display(Name = "Option 2")]
   OptionTwo=2
}

If not, how can I make the Display Name for an enum variable ?

Do you mean how to use [attributes](http://stackoverflow.com/q/1799370/1997232) with `enum`? — Sinatr, Oct 17 '14 at 12:18
@Sinatr well I guess Display is an attribute. Updated question. — general exception, Oct 17 '14 at 12:20
I dont think that you can make them variable, they need to be known at compile time — David Pilkington, Oct 17 '14 at 12:21
@DavidPilkington I need to change the display name based on a value elsewhere. — general exception, Oct 17 '14 at 12:22
I am using the DisplayName to render a radio button label on an MVC view. I need this to change based on a set value somewhere. Is there a different approach I can take ? — general exception, Oct 17 '14 at 12:23
Yes. Create method, use switch to return formatted text by runtime value. — Renatas M., Oct 17 '14 at 12:25

Michal Hosala · Accepted Answer · 2014-10-17T14:33:55.233

Seems like nobody's dealing with:

If not, how can I make the Display Name for an enum variable ?

I can think about some kind of enum map plus extension method which could work like this:

using System;
using System.Collections.Generic;
namespace ConsoleApplication1
{
    public enum Foo
    {
        One = 1,
        Two = 2,
    }

    public static class ExtensionMethods
    {
        private static readonly Dictionary<Enum, string> s_EnumMap = new Dictionary<Enum, string>
            {
                { Foo.One, string.Format("{0} - {1}","Option One", 1) },
                { Foo.Two, string.Format("{0} - {1}","Option Two", 2) }
            };

        public static String ConvertToString(this Enum eff)
        {
            return s_EnumMap[eff];
        }
    }

    internal class Program
    {
        private static void Main(string[] args)
        {
            Console.WriteLine(Foo.One.ConvertToString());
            Console.WriteLine(Foo.Two.ConvertToString());
        }
    }
}

Integers 1 and 2 can be of course replaced by e.g. static variable, such as MyClass.myVariable. If that is the way you would use this code, then keep in mind that s_EnumMap will store the values that MyClass.myVariable variable had at the time when you first used ExtensionMethods class (i.e. when static fields of MyClass were getting initialized). So modifying the code like this:

public MyClass
{
    public static int myVariable = 5;
}

public static class ExtensionMethods
{
    private static readonly Dictionary<Enum, string> s_EnumMap = new Dictionary<Enum, string>
        {
            { Foo.One, string.Format("{0} - {1}","Option One", MyClass.myVariable) },
            { Foo.Two, string.Format("{0} - {1}","Option Two", 2) }
        };

    public static String ConvertToString(this Enum eff)
    {
        return s_EnumMap[eff];
    }
}

internal class Program
{
    private static void Main(string[] args)
    {
        Console.WriteLine(Foo.One.ConvertToString());
        Console.WriteLine(Foo.Two.ConvertToString());
        MyClass.myVariable = 100;
        Console.WriteLine(Foo.One.ConvertToString());
        Console.WriteLine(Foo.Two.ConvertToString());
    }
}

Would result into:

Option One - 5
Option Two - 2
Option One - 5
Option Two - 2

While after commenting out the first two Console.WriteLines, the output would be:

Option One - 100
Option Two - 2

So if you want to dynamicaly react to changes of MyClass.myVariable then you have to implement some logic to update s_EnumMap`, but as long as I don't know more about the goal you are trying to achieve I cannot provide a better answer.

Rufus L · Answer 2 · 2014-10-17T13:07:39.717

You could write a separate method to get the display name, or even a small class that has an option member and a display name member. I like Michal's idea better, but since I already started writing this I figured I'd throw it out there!

public enum Option
{
    OptionOne = 1,
    OptionTwo = 2
}

public static string GetOptionDisplayName(Option option)
{
    switch (option)
    {
        case Option.OptionOne:
            return string.Format("{0} - {1}", "Option One", MyClass.MyProperty);
        case Option.OptionTwo:
            return string.Format("{0} - {1}", "Option Two", MyClass.MyProperty);
        default:
            return option.ToString();
    }
}

public class AnotherOption
{
    public Option Option { get; set; }

    public string DisplayName
    {
        get { return GetOptionDisplayName(this.Option); }
    }
}

score 0 · Answer 3 · answered Oct 17 '14 at 12:24

0

What you want cannot be done. The compiler needs to know the value at compile time.

answered Oct 17 '14 at 12:24

David Pilkington

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score 0 · Answer 4 · answered Oct 17 '14 at 12:25

The short answer no. The value within [Display....] can be known at compile time only. E.g. you can define literals, like string or enum value. string.Format() is called at run time. If possible you should call it in you other logic, using you enum. Or use code generating, e.g. with a tt template

Enum Display Name - Use variable?

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