Using LINQ to foreach over an enum in C#

April 10th 2008 • .NET (, ) • 7,297 views • 7 responses

I can’t be the only person in the world who wants to foreach over the values of an enum otherwise Enum.GetValues(Type enumType) wouldn’t exist in the framework. Alas it didn’t get any generics love in .NET 2.0 and unhelpfully returns an array.

Thanks to the power of LINQ you can do this:

foreach(CustomerTypes customerType in Enum.GetValues(typeof(CustomerTypes)).Cast<CustomerTypes>())

That is okay, but this is more concise:

foreach(CustomerTypes customerType in Enums.Get<CustomerTypes>())

The tiny class to achieve that is, of course:


using System.Collections.Generic;
using System.Linq;

public static class Enums {
	public static IEnumerable<T> Get<T>() {
		return System.Enum.GetValues(typeof(T)).Cast<T>();
	}
}

Great.

[)amien

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7 responses  

  1. Guy on April 10th, 2008

    Great post and valuable information – bookmarked and will be used in the future. :)

    Question: Is it actually the power of LINQ that you’re using? i.e. Are extension methods part of LINQ or are they part of C# 3.0?

  2. Damien Guard on April 10th, 2008

    Good question!

    LINQ uses some specific compiler magic for the select/in/where/order keywords and also has a bunch of classes in the System.Linq namespace.

    To achieve the functionality requires these classes use Extension methods quite extensively. It also takes advantage of Lambda expressions, anonymous types and is demonstrated often using type inference, all C# 3.0 features!

    [)amien

  3. Steve on April 10th, 2008

    Yuck. Equivalent Java code:

    for (CustomerTypes customerType : CustomerTypes.values())

    One of the rare occasions Java is more concise than C#, obviously ;)

  4. Damien Guard on April 12th, 2008

    That’s nice! (hope you don’t mind me reformatting it). I did consider going with an extension method but my worry was having .Values appear for all classes.

    [)amien

  5. Richard on April 12th, 2008

    You can make use of an extension method to make this slightly nicer… but you call the extension against an instance of the enum (naming for the extension needs to be better):

    
using System;
using System.Collections.Generic;
using System.Linq;

static class Enums {
	public static IEnumerable<T> Values<T>(this T en) where T : struct {
		if (!typeof(T).IsEnum)
			throw new InvalidOperationException();
		foreach (var x inEnum.GetValues(typeof(T)).Cast<T>())
			yield return x;
	}
}

enum Test { One, Two, Three }

class Program {
	static void Main(string[] args) {
		IEnumerable<Test> t = Test.One.Values();
		foreach (var x in t)
			Console.WriteLine(x);
	}
}
  6. Richard on April 13th, 2008

    > hope you don’t mind me reformatting it

    No problem.

    This is the second time I would have liked to write an extension method that extends the target’s static methods (rather than instance).

  7. Florent on April 15th, 2008

    Hi guys :)
    I think that “Cast” method is not mandatory… In fact, you can directly cast that Enum.GetValues return into IEnumerable. Because it’s a simple array :)
    So you can do like this:

    IEnumerable<T> myEnumerableOfEnum = (IEnumerable<T>)Enum.GetValues(typeof(T));

    But you can do this too:

    IList<T> myListOfEnum = (IList<T>)Enum.GetValues(typeof(T));
T[] myArrayOfEnum = (T[])Enum.GetValues(typeof(T));

    I hope this will useful :)

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  2. (kept private)