Help in creating Enum extension helper

Question

Take this enum for example:

public enum PersonName : short
{
    Mike = 1,
    Robert= 2
}

I wnat to have en extension method like this:

PersonName person = PersonName.Robert;
short personId = person.GetId();
//Instead of:
short personId = (short)person;

Any idea how to implement this?

it need to be generic to int, short etc..., and to generic enums as well, not limited to PersonName.

Answer 1

I believe you should be able to define an extension mehtod on the PersonName class:

public static class PersonExtensions // now that sounds weird...
{
    public static short GetID (this PersonName name)
    {
        return (short) name;
    }
}

Side node: I somehow hope that the code in your question is overly simplified, as it does not seem quite right to implement a person repository as an enum :)

Answer 2

Is there any reason you can't turn it into a class? It would probably make more sense in context of a class.

Answer 3

I would just use something like IEnumerable<KeyValuePair<string,short>> or Dictionary<string,short>... you can add your extensions to IDictionary or IEnumerable if you want.

Answer 4

This is completely impossible.

You cannot constrain a method based on an enum's underlying type.

Explanation:

Here is how you might try to do this:

public static TNumber GetId<TEnum, TNumber>(this TEnum val) 
       where TEnum : Enum 
       where TEnum based on TNumber

The first constraint is unfortunately not allowed by C#, and the second constraint is not supported by the CLR.