Convert from List into IEnumerable format

Question

IEnumerable<Book> _Book_IE
List<Book> _Book_List

How shall I do in order to convert _Book_List into IEnumerable format?

For people wondering why Kirk's comment have so many "ups", it's because you can't just name your variable the way you want ! there are conventions for that, and it is highly recommended that you follow them, so that your code can be clear and understandable, this will help the people trying to help you in places like Stack-overflow or GitHub! for further information read the book : **Clean Code** by Robert C. Martin. — KADEM Mohammed, May 09 '20 at 07:11
...and how to go about a naming convention without falling prey to the Smurf Naming anti-pattern? https://devcards.io/smurf-naming-convention Typically a namespace can provide specificity where needed. — Meadock, May 19 '20 at 13:17
Convertint to ienumerable is specially useful when you need to use the .Reverse() in a Linq expression — Zuabros, Sep 08 '20 at 21:06

score 192 · Accepted Answer · edited Mar 26 '18 at 19:45

192

You don't need to convert it. List<T> implements the IEnumerable<T> interface so it is already an enumerable.

This means that it is perfectly fine to have the following:

public IEnumerable<Book> GetBooks()
{
    List<Book> books = FetchEmFromSomewhere();    
    return books;
}

as well as:

public void ProcessBooks(IEnumerable<Book> books)
{
    // do something with those books
}

which could be invoked:

List<Book> books = FetchEmFromSomewhere();    
ProcessBooks(books);

edited Mar 26 '18 at 19:45

CJBS

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answered Jan 15 '11 at 16:13

Darin Dimitrov

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If you function returns a Task> and you try to return Task.FromResult(list_of_books) this will not work. I used the AsEnumerable extension method to come around this. – Daniel Apr 24 '23 at 13:07

cdie · Answer 2 · 2017-11-17T13:04:29.277

109

You can use the extension method AsEnumerable in Assembly System.Core and System.Linq namespace :

List<Book> list = new List<Book>();
return list.AsEnumerable();

This will, as said on this MSDN link change the type of the List in compile-time. This will give you the benefits also to only enumerate your collection we needed (see MSDN example for this).

edited Nov 17 '17 at 13:04

answered Mar 21 '16 at 15:06

cdie

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Looks simple but makes easiest way to convert. Thank you – Ishwor Khanal Aug 01 '17 at 11:51
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If you are not suppose to add something to the Collection then you should use/return IEnumerable. – AZ_ Jun 25 '19 at 08:38
using System.Linq; – Dev-lop-er Oct 20 '21 at 07:06

score 18 · Answer 3 · answered Nov 23 '13 at 09:05

18

Why not use a Single liner ...

IEnumerable<Book> _Book_IE= _Book_List as IEnumerable<Book>;

answered Nov 23 '13 at 09:05

Rahul Chowdhury

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score 11 · Answer 4 · answered Jan 15 '11 at 16:13

11

As far as I know List<T> implements IEnumerable<T>. It means that you do not have to convert or cast anything.

answered Jan 15 '11 at 16:13

Elalfer

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It depends. If you try to set a `IEnumerable>` to an `IEnumerable>` it gives a compiler error since the second does not inherit from the first one. – Emaborsa Jul 24 '17 at 11:08

score 6 · Answer 5 · answered Jan 15 '11 at 16:13

6

IEnumerable<Book> _Book_IE;
List<Book> _Book_List;

If it's the generic variant:

_Book_IE = _Book_List;

If you want to convert to the non-generic one:

IEnumerable ie = (IEnumerable)_Book_List;

answered Jan 15 '11 at 16:13

Femaref

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You don't need the cast here. – Jon Skeet Jan 15 '11 at 16:44
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You do if you want the specific methods from the non-generic interface, as some of them are explicitly implemented, or am I'm on the wrong track here? – Femaref Jan 15 '11 at 20:45

score 0 · Answer 6 · answered Jul 06 '17 at 10:58

0

You need to

using System.Linq;

to use IEnumerable options at your List.

answered Jul 06 '17 at 10:58

Jury

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Convert from List into IEnumerable format

6 Answers6

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