.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
{
Red,
Yellow,
Green
}
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):
type
TTrafficLightColors = (Red, Yellow, Green);
var
TrafficLightColor: TTrafficLightColors;
begin
for TrafficLightColor := Low(TTrafficLightColors) to High(TTrafficLightColors) do
// some business logic
end;
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)
Console.WriteLine(color);
I’d much rather write code like this using the TrafficLightColors type much less:
TrafficLightColors[] colorsArray = EnumHelper.EnumToArray<TrafficLightColors>();
foreach (TrafficLightColors color in colorsArray)
Console.WriteLine(color);
List<TrafficLightColors> colorsList = EnumHelper.EnumToList<TrafficLightColors>();
foreach (TrafficLightColors color in colorsList)
Console.WriteLine(color);
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.
–jeroen
The Wiert Corner - irregular stream of stuff 
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