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.NET/C# – an easier foreach for enums using generic methods

Posted by jpluimers on 2009/04/28

I like enums. Maybe because of my Turbo Pascal and Delphi background. They are descriptive. Makes code easier to read.

        public enum TrafficLightColors

But using them in C# foreach loops is a bit of a pain, not so much in the loop itself, but more in getting the list of values to loop over.

The Delphi equivalent would be like this, including a loop to run through all of the enumeration values (note that in Delphi, it us good practice to start types with a T):

  TTrafficLightColors = (Red, Yellow, Green);
  TrafficLightColor: TTrafficLightColors;
  for TrafficLightColor := Low(TTrafficLightColors) to High(TTrafficLightColors) do
    // some business logic

Quite a while ago, I was fed up writing code to get the list of values like below; it felt much to awkward, and way too many occasions of the TrafficLightColors type, so this is an excellent candidate to simplify using use C# Generics.

            Array values = Enum.GetValues(typeof(TrafficLightColors));
            TrafficLightColors[] colorsArray = (TrafficLightColors[])values;
            foreach (TrafficLightColors color in colorsArray)

I’d much rather write code like this using the TrafficLightColors type much less:

            TrafficLightColors[] colorsArray = EnumHelper.EnumToArray<TrafficLightColors>();
            foreach (TrafficLightColors color in colorsArray)

            List<TrafficLightColors> colorsList = EnumHelper.EnumToList<TrafficLightColors>();
            foreach (TrafficLightColors color in colorsList)

In fact, I’d even hoped that extension methods would eliminate the use of the reference to EnumHelper but explaining that will be part of a future blog.

So lets end with the tiny EnumHelper class:

using System;
using System.Collections.Generic;

namespace bo.Generic
    public class EnumHelper
        public static T[] EnumToArray<T>()
            Array values = Enum.GetValues(typeof(T));
            T[] result = (T[])values;
            return result;

        public static List<T> EnumToList<T>()
            T[] array = EnumToArray<T>();
            List<T> result = new List<T>(array);
            return result;

That should get you going simplifying your enum based foreach loops.


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