extend enum with attribute in other assembly

Question

There exists an enum in an assembly:

public enum TheEnumeration
{
    TheFirstValue = 1,
    TheSecondValue = 2
}

In another Assembly I would like to extend this enumeration with some Attributes (I know this is not valid code, just to show the idea):

public enum MyExtendedEnumeration : TheEnumeration
{
    [MyAttribute("The First Value")]
    TheFirstValue,

    [MyAttribute("The 2nd Value")]
    TheSecondValue
}

Is there a way to achieve this goal in a proper way?

Not the way you want - you cannot extend or inherit from enums. What do you intend to use the attribute for? — D Stanley, Sep 24 '14 at 13:54
utilmately, it looks like you might be able to do with the standard `DescriptionAttribute` — Ňɏssa Pøngjǣrdenlarp, Sep 24 '14 at 18:05
@Plutonix How might I be able to do this with DescriptionAttribute if inheriting from the base enum is not possible (achording to the existings answers)? Can you give me an example in the answers? — Roland Bär, Sep 25 '14 at 09:58
basically see reckface's answer, but use `Description` in place of `MyAttribute` if you simply need to associate some text to a version of it. — Ňɏssa Pøngjǣrdenlarp, Sep 25 '14 at 12:10

score 1 · Accepted Answer · edited May 23 '17 at 12:05

You can't Extend enums, you can't inherit from them. You may just have to create a new Enum that repeats the values like a pass through and then decorate yours.

public enum MyExtendedEnumeration
{
    [MyAttribute("The First Value")]
    TheFirstValue = TheEnumeration.TheFirstValue,

    [MyAttribute("The 2nd Value")]
    TheSecondValue = TheEnumeration.TheFirstValue
}

See: Extending enums in c#

score 0 · Answer 2 · answered Sep 24 '14 at 14:14

Enums cant inherit from another Enum. They are based on the System.Enum You can put Attributes on the members.

Creating a class/Type that behaves somewhat like an Enum, may be a useful in scenarios like this. Assumes you can "alter" the orginal enum.

///
/// Sample of a STRING or non int based enum concept.
/// 

public sealed class FilterOp {
    private static readonly Dictionary<string, FilterOp> EnumDictionary = new Dictionary<string, FilterOp>();
    private readonly string _name;
    private readonly string _value;

    public const string Eq = "Eq";
    public const string Ne = "Ne";
    public const string Gt = "Gt";
    public const string Ge = "Ge";
    public const string Lt = "Lt"; 
    public const string Le = "Le";
    public const string And = "And";
    public const string Or = "Or";
    public const string Not = "Not";

    public static readonly FilterOp OpEq = new FilterOp(Eq);
    public static readonly FilterOp OpNe = new FilterOp(Ne);
    public static readonly FilterOp OpGt = new FilterOp(Gt);
    public static readonly FilterOp OpGe = new FilterOp(Ge);
    public static readonly FilterOp OpLt = new FilterOp(Lt);
    public static readonly FilterOp OpLe = new FilterOp(Le);
    public static readonly FilterOp OpAnd = new FilterOp(And);
    public static readonly FilterOp OpOr = new FilterOp(Or);
    public static readonly FilterOp OpNot = new FilterOp(Not);


    private FilterOp(string name) {
        // extend to cater for Name / value pair, where name and value are different
        this._name = name;
        this._value = name;
        EnumDictionary[this._value] = this;
    }

    public override string ToString() {
        return this._name;
    }

    public string Name {
        get { return _name; }
    }

    public string Value {
        get { return _value; }
    }

    public static explicit operator FilterOp(string str) {
        FilterOp result;
        if (EnumDictionary.TryGetValue(str, out result)) {
            return result;
        }
        return null;
    }
}

extend enum with attribute in other assembly

2 Answers2