Proposal: Class-level enum (as in Java)

[chergey]

As is known, Java has full-fludged enums (with constructors, methods). Why not add that to C# ?
Of course, we can always declare a new class to simulate enums but this feature would render that reduntant.

public enum SimpleEnum {
//constuction of values
    Nomencl("nomencl", "nomencl" ),
    Company("organization", "company");
//actually, values
    String SK, DK;

    SimpleEnum(String key, String dbkey) {
        this.SK = key;
        this.DK=dbkey;
    }
    String S() {
        return SK + "Name";
    }

    String S1() {
        return SK + "Code";
    }

    static public String ConvertType(String type)
    {
        if (type.equals(ColTypes.Nomencl.SV))
            return ColTypes.Nomencl.DK;
        else  if (type.equals(ColTypes.Company.SV))
            return ColTypes.Company.DK;

        return "";
    }
};

[HaloFour]

Check out the conversation about this on the Roslyn repo:

dotnet/roslyn#6739

Of specific interest might be that Oracle owns a patent on Java's implementation of enums, so Microsoft would not be able to implement the same construct in C#:

https://www.google.com/patents/US7263687

[erik-kallen]

Perhaps it's best to wait with this feature until 2028, then.

[The-Futurist]

@elcergey - I disagree that Java has a "full fledged enum". Technically Java has a special kind of static class with special interface characteristics that the language designer chose to refer to as an enum. Just because the Java team called this an enum doesn't mean that this somehow redefines the meaning of "enum". C, C++ and Pascal support enums and enumerated types that are pretty much the same as we have in C#.

It might be a good idea to give C# something similar but I would not advocate changing the definition of enum but rather introduce a new term or express the concept using existing terms but perhaps in a new way.

[jnm2]

Of specific interest might be that Oracle owns a patent on Java's implementation of enums, so Microsoft would not be able to implement the same construct in C#:

https://www.google.com/patents/US7263687

That's totally sick.

[YaakovDavis]

Microsoft would not be able to implement the same construct in C#

I'm not sure I'm sad about this.

[fanoI]

One example of a thing should have been an enum and instead is a struct is System.Drawing.Color that needing to have methods (for example the one that converts the color to an ARGB int) and properties (A, R, G, B for example) needed to be a stuct with a "complex" system to construct a new Color starting from "KnowColors".

Maybe adding the possibility to add extensions methods to enum could in part solve the issue but code it like a class / struct would be perfect but how to do this without infringe Oracle copyright?

[alrz]

I think dotnet/roslyn#3704 is not under that patent (or is it?).

[chergey]

@alrz Two years have passed since then, still nothing.

[HaloFour]

@alrz

Probably not. If we were going down this path I'd rather pursue similar functionality to Apple Swift's enums, which also gets us some nice syntax for closed ADTs.

@elcergey

You can only eat an elephant one bite at a time.

[Thaina]

Might related #144

[pie-flavor]

Good syntax for this is enum class (borrowed from Kotlin). Also, I have found a great many instances where this would have come in handy, most notably overriding object.ToString() and similar. I am surprised this issue has received as little activity as it has.

[robsosno]

Oracle's enum patent expires at the beginning of 2024. So new enum class could be placed in the scope of .NET 9. IMO it would be beneficial to C# language to have this feature.

[saint4eva]

If DU had already been done before then, no need for enum class any longer.

[sliekens]

@saint4eva that's wishful thinking.