Comments on: Using LINQ to foreach over an enum in C# http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c?utm_source=rss&utm_medium=rss&utm_campaign=using-linq-to-foreach-over-an-enum-in-c A .NET developer in silicon valley Fri, 18 May 2012 15:31:00 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Jesse Pakin http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-42631 Jesse Pakin Tue, 09 Nov 2010 04:43:42 +0000 http://damieng.com/?p=901#comment-42631 Thanks for the post. I was able to use it along with <a href="http://weblogs.asp.net/stefansedich/archive/2008/03/12/enum-with-string-values-in-c.aspx" rel="nofollow">another posting regarding custom attributes </a> to list out friendly names for enums in a dropdown, in a view in an MVC project (with a nice bit of LINQ). <pre><code><%: Html.DropDownList("CardRecord.Type",((IList<CreditCardType>)Enum.GetValues(typeof(CreditCardType))).Select(s => new SelectListItem{Text = s.GetStringValue(), Value = s.ToString()}))%></code></pre> Thanks for the post. I was able to use it along with another posting regarding custom attributes
 to list out friendly names for enums in a dropdown, in a view in an MVC project (with a nice bit of LINQ).

<%: Html.DropDownList("CardRecord.Type",((IList<CreditCardType>)Enum.GetValues(typeof(CreditCardType))).Select(s => new SelectListItem{Text = s.GetStringValue(), Value = s.ToString()}))%>
]]> By: Florent http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8263 Florent Tue, 15 Apr 2008 14:56:12 +0000 http://damieng.com/?p=901#comment-8263 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: <pre><code>IEnumerable<T> myEnumerableOfEnum = (IEnumerable<T>)Enum.GetValues(typeof(T));</code></pre> But you can do this too: <pre><code>IList<T> myListOfEnum = (IList<T>)Enum.GetValues(typeof(T)); T[] myArrayOfEnum = (T[])Enum.GetValues(typeof(T)); </code></pre> I hope this will useful :) 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 :)

]]> By: Richard http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8242 Richard Sun, 13 Apr 2008 07:37:21 +0000 http://damieng.com/?p=901#comment-8242 > 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). > 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: Richard http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8238 Richard Sat, 12 Apr 2008 15:56:01 +0000 http://damieng.com/?p=901#comment-8238 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): <pre><code> <strong>using</strong> System; <strong>using</strong> System.Collections.Generic; <strong>using</strong> System.Linq; <strong>static class</strong> Enums { <strong>public static </strong>IEnumerable<T> Values<T>(<strong>this</strong> T en) <strong>where</strong> T : <strong>struct</strong> { <strong>if</strong> (!<strong>typeof</strong>(T).IsEnum) <strong>throw new</strong> InvalidOperationException(); <strong>foreach</strong> (<strong>var</strong> x <strong>in</strong>Enum.GetValues(typeof(T)).Cast<T>()) <strong>yield return</strong> x; } } <strong>enum</strong> Test { One, Two, Three } <strong>class</strong> Program { <strong>static void</strong> Main(<strong>string</strong>[] args) { IEnumerable<Test> t = Test.One.Values(); <strong>foreach</strong> (<strong>var</strong> x <strong>in</strong> t) Console.WriteLine(x); } } </code></pre> 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: Damien Guard http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8239 Damien Guard Sat, 12 Apr 2008 09:30:01 +0000 http://damieng.com/?p=901#comment-8239 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 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: Steve http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8203 Steve Thu, 10 Apr 2008 21:25:13 +0000 http://damieng.com/?p=901#comment-8203 Yuck. Equivalent Java code: for (CustomerTypes customerType : CustomerTypes.values()) One of the rare occasions Java is more concise than C#, obviously ;) Yuck. Equivalent Java code:

for (CustomerTypes customerType : CustomerTypes.values())

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

]]> By: Damien Guard http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8199 Damien Guard Thu, 10 Apr 2008 19:56:37 +0000 http://damieng.com/?p=901#comment-8199 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 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 http://damieng.com/blog/2008/04/10/using-linq-to-foreach-over-an-enum-in-c#comment-8198 Guy Thu, 10 Apr 2008 19:26:18 +0000 http://damieng.com/?p=901#comment-8198 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? 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?

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