Extension method on enumeration, not instance of enumeration

Question

I have an enumeration for my Things like so:

public enum Things
{
   OneThing,
   AnotherThing
}

I would like to write an extension method for this enumeration (similar to Prise's answer here) but while that method works on an instance of the enumeration, ala

Things thing; var list = thing.ToSelectList();

I would like it to work on the actual enumeration instead:

var list = Things.ToSelectList();

I could just do

var list = default(Things).ToSelectList();

But I don't like the look of that :)

I have gotten closer with the following extension method:

public static SelectList ToSelectList(this Type type)
{
   if (type.IsEnum)
   {
      var values = from Enum e in Enum.GetValues(type)
                   select new { ID = e, Name = e.ToString() };
      return new SelectList(values, "Id", "Name");
   }
   else
   {
      return null;
   }
}

Used like so:

var list = typeof(Things).ToSelectList();

Can we do any better than that?

Answer 1

No.

The best you can do is put it on a static class, like this:

public static class ThingsUtils { 
    public static SelectList ToSelectList() { ... }
}

Answer 2

Extension methods only work on instances, so it can't be done, but with some well-chosen class/method names and generics, you can produce a result that looks just as good:

public class SelectList
{
    // Normal SelectList properties/methods go here

    public static Of<T>()
    {
        Type t = typeof(T);
        if (t.IsEnum)
        {
            var values = from Enum e in Enum.GetValues(type)
                         select new { ID = e, Name = e.ToString() };
            return new SelectList(values, "Id", "Name");
        }
        return null;
    }
}

Then you can get your select list like this:

var list = SelectList.Of<Things>();

IMO this reads a lot better than Things.ToSelectList().