Comments on: Using LINQ to foreach over an enum in C#

By: Florent

Florent — Tue, 15 Apr 2008 06:58:35 +0000

Oups... T argument is missing :)
You should read as:
IEnumerable&lgtT&rgt myEnumerableOfEnum = (IEnuemrable&lgtT&rgt)Enum.GetValues(typeof(T));
and:
IList&lgtT&rgt myListOfEnum = (IList&lgtT&rgt)Enum.GetValues(typeof(T));

By: Florent

Florent — Tue, 15 Apr 2008 06:56:12 +0000

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 myEnumerableOfEnum = (IEnuemrable)Enum.GetValues(typeof(T));
But you can do this too:
IList myListOfEnum = (IList)Enum.GetValues(typeof(T));
T[] myArrayOfEnum = (T[])Enum.GetValues(typeof(T));

I hope this will usefull :)

By: Richard

Richard — Sun, 13 Apr 2008 07:37:21 +0000

> 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).

By: Damien Guard

Damien Guard — Sat, 12 Apr 2008 09:30:01 +0000

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

By: Richard

Richard — Sat, 12 Apr 2008 07:56:01 +0000

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);
	}
}

By: Steve

Steve — Thu, 10 Apr 2008 21:25:13 +0000

Yuck. Equivalent Java code:

for (CustomerTypes customerType : CustomerTypes.values())

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

By: Damien Guard

Damien Guard — Thu, 10 Apr 2008 19:56:37 +0000

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

By: Guy

Guy — Thu, 10 Apr 2008 19:26:18 +0000

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?