Enum with methods for functionality (Combine Class / Enum)

Question

I may miss some sort of point here, if that's the case - please include that discussion as a part of my question :).

This is a shortened down and renamed sample of a working code. The GetTicks(…) is a single sample, which could be any sort of functionality (value of > 0 < 9 should return a specific Enum a.so).

public static class Something {     public enum TypeOf : short     {         Minute = 2, Hour = 3, Day = 4, …     }      public static long GetTicks(Something.TypeOf someEnum)     {         long ticks = 0;         switch (someEnum)         {             case Something.TypeOf.Minute:                 ticks = TimeSpan.TicksPerMinute;                 break;             case Something.TypeOf.Hour:                 ticks = TimeSpan.TicksPerHour;                 break;          ....         }         return ticks;     } }  // This class is called from anywhere in the system. public static void SomeMethod(string dodo, object o, Something.TypeOf period) {     // With the design above     long ticks = Something.GetTicks(period);      // Traditional, if there was a simple enum     if (period == Something.Day)         ticks = TimeSpan.FromDays(1).Ticks;     else if (period == Something.Hour)         ticks = TimeSpan.FromHours(1).Ticks; } 

The idea is to collect functionality that concerns an enum, near as possible to the enum itself. The enum is the reason function. Also, I find it easy and natural to look for such functionality near the enum. Also, it's easy to modify or extend.

The drawback I have is that I have to state the enum more explicit, like Something.TypeOf. The design may look non-standard? And would it apply, if the enum was for internal use in the class.

How would you do this more nicely? I tried abstract, base inheritance, partial. None of them seem to apply.

Answer 1

If you don't mind a little more writing you can make extension methods to expand the interface of the enum.

e.g.

public enum TimeUnit {    Second,    Minute,    Hour,    Day,    Year,    /* etc */ } public static class TimeUnitExtensions {     public static long InTicks(this TimeUnit myUnit)     {          switch(myUnit)          {            case TimeUnit.Second:                return TimeSpan.TicksPerSecond;            case TimeUnit.Minute:                return TimeSpan.TicksPerMinute;             /* etc */          }     } } 

This can add "instance" methods to your enums. It's a bit more verbose than mostly liked, though.

Remember though that an enum should be treated mostly as a named value.

Answer 2

C# enums don't work well like this. However, you can implement your own "fixed set of values" fairly easily:

public sealed class Foo {     public static readonly Foo FirstValue = new Foo(...);     public static readonly Foo SecondValue = new Foo(...);      private Foo(...)     {     }      // Add methods here } 

As it happens, one example I've got of this is remarkably similar to yours - DateTimeFieldType in Noda Time. Sometimes you might even want to make the class unsealed, but keep the private constructor - which allows you to create subclasses only as nested classes. Very handy for restricting inheritance.

The downside is that you can't use switch :(