which is efficient in this case? LINQ query or FOREACH loop?

Question

2.50/5 (2 votes)

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in my project i implemented a service class which has a function naming GetList() which is as follows:

XML

IList<SUB_HEAD> GetList(string u)
{
    var collection = (from s in context.DB.SUB_HEAD where (s.head_code.Equals(u))
    select s);
    return collection.ToList();
}

drpdwn.datasource=Getlist();
drpdwn.databind();

which can also b implemented as

C#

Arraylist unitlist= new Arraylist();
ObjectSet<SUB_HEAD> List = subheadService.GetAll();
foreach(SUB_HEAD unit in List)
{
    unitlist.Add(unit.sub_head_code);
}

drpdwn.datasource=unitlist;
  drpdwn.databind();

Purpose of doing this is to populate dropdown menu.

My question is that "which of the above method will be more efficient with respect to processing?" because my project have lot of places where i have to use drop down menu.

Posted 3-Feb-14 7:36am

Basit Elahi

Updated 3-Feb-14 8:59am

v3

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Comments

Matt T Heffron 3-Feb-14 13:46pm

These two code fragments are NOT equivalent.
The first one is comparing strings and the second is not.
Apples and Oranges...

Basit Elahi 3-Feb-14 15:01pm

i know it is not same and for the same reason i have mentioned at the end that both of these are used to populate drop down list. Now i have improved the question. Please check out the latest one

Sergey Alexandrovich Kryukov 3-Feb-14 15:07pm

What prevents you from timing both cases (after you make sure they give you identical results)? Overall performance may depend on different factors and be better for one technique in one case, and better for another technique for another case.
—SA

BillWoodruff 3-Feb-14 21:55pm

I sometimes think a large percentage of QA questions should be answered like this, by suggestions for what the inquirer can DO to answer the question for themselves, perhaps with a link ... in this case, perhaps, a link to a how-to-time .NET operations CodeProject article.

As the old saying goes: "give a man a fish, and you feed him for a day; teach a man to fish, and you feed him for a lifetime."

But, then, that wouldn't be CodeProject ... would it ?

Sergey Alexandrovich Kryukov 3-Feb-14 22:01pm

Absolutely! I already answered with this wise proverb after someone blamed me for providing not quite a complete solution.

Would it be CodeProject? I am quite sure it will. CodeProject is already like that. It's a mix of relatively bad and relatively good answers. Using the idea you just expressed (if we do it properly, depending on question and our understanding of the inquirer's background), we can only improve the ratio.

—SA

BillWoodruff 3-Feb-14 22:42pm

I did write that response somewhat "tongue in cheek:" I do think a valuable thing programmers who are "veterans" with a given technology stack have to share is "heuristic" knowledge, strategic knowledge, which is often based on hard-won struggles to work-around the quirks, and inconsistencies, of implementation related to language features, built-in Controls behavior, etc.

So, I do think "best way" questions are quite valid; the problem, imho, is in, for a given question, assessing whether the person asking is just another goof-off who hasn't done their homework, or is someone who is seriously trying to learn.

The motivation and "state" of the questioner can be very difficult to assess if they are not native English speakers.

CoderPanda 3-Feb-14 23:26pm

Interesting and useful debate though I am afraid it will start another SO vs CP debate. I personally prefer something that is in between these two.

I totally agree with guiding the poster towards the answer than writing code for them, however I did try it few times and promptly got down-voted :)

Sergey Alexandrovich Kryukov 4-Feb-14 0:18am

About good-offs and other unreasonable inquirers is a good point; and here is what I think. Everyone deserves a chance. How can we takes out the change? One of the way is write out a complete answer without inviting to learn, think and do some work. It would be not very respectful "eat-it-and-shut-up" approach. Why wasting time for that? At first, any person deserves more respectful approach, which is more like "you can do it". Just think a bit. Read. Learn. If it did not work, or works rarely, it still worth trying. If thousand of people look hopeless, helping just one of them who managed to step over the laziness (or impudence, or whatever else) is already a worthy result.

And not only at first. I already faced some rare cases where some inquirers who behaved lazily and looked hopeless at first, changed their minds later, at least to some degree, and started to improve. Doesn't it mean something?

—SA

CoderPanda 4-Feb-14 1:07am

Absolutely, couldn't agree more.

Matthew Dennis 3-Feb-14 15:35pm

You could also do
string u = "...";
drpdwn.datasource = context.DB.SUB_HEAD.Where(x => x.head_code == u).ToList();

BillWoodruff 3-Feb-14 21:48pm

If you are confident this works, why not post this as a "solution" ?

Matthew Dennis 4-Feb-14 11:25am

It's not a solution, just another way to do it.

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CoderPanda · Answer 1 · 2014-02-03T19:16:00

Solution 1

As a general rule of thumb I prefer for loop over foreach loop over LINQ; that is from Performance point of view.

See this[^] and this[^]

[Please encourage participation by up-voting solutions or answers that work for you]

Posted 3-Feb-14 19:16pm

CoderPanda

Updated 3-Feb-14 19:39pm

v2

Matthew Dennis · Answer 2 · 2014-02-04T05:31:00

From the looks of your code, you are retrieving the menu content from the database and are concerned about performance.
If that is the case, then the best solution is to not make the call to the database.
Load the various dropdown menus from the database at startup and store the results in a dictionary.
The dictionary could be a Lazy loaded static application wide object.
Alternately, store the menus by key (u) in the cache and reload and cache if not in cache. This has the advantage of allowing you to set a cache timeout, forcing the menus to be refreshed on a regular basis, allowing for menu (database) changes without having to restart the app.