Convert foreach loop with repeater in linq

Question

How can I convert below code in LINQ

foreach (RepeaterItem ri in rptNews.Items)
            {
                HiddenField hdnUserId = (HiddenField)ri.FindControl("hdnId");
                int userId = Users.Current.UserId;
                if (Convert.ToInt32(hdnUserId.Value) != userId)
                {
                    ((ImageButton)ri.FindControl("img1")).Visible = false;
                    ((ImageButton)ri.FindControl("img2")).Visible = false;

                }

            }

Also please guide me how can I learn to translate this kind of code to linq.

Why do you want to "translate" this code into LINQ? It looks fine as it is. LINQ is not the solution to every problem. — Frédéric Hamidi, Jan 13 '12 at 10:20
I read that Linq is faster and I have so many items in repeater. So I thought LINQ can work better than traditional foreach loop. I am not sure because I am new to linq :-( — Zerotoinfinity, Jan 13 '12 at 10:21
Whether or not LINQ is faster is irrelevant if what you have now is readable and fast enough. — George Duckett, Jan 13 '12 at 10:23
Given that LINQ is not intended for causing side-effects, you really should loop somewhere. — spender, Jan 13 '12 at 10:23
I am confused now because of my limited knowledge in LINQ. Does that mean that foreach is best in this case ? — Zerotoinfinity, Jan 13 '12 at 10:25
@Zerotoinfinite LINQ is NOT faster than foreach or for loops. http://stackoverflow.com/questions/3156059/linq-statement-faster-than-foreach-loop — giammin, Jan 13 '12 at 10:30
@Zerotoinfinite, `foreach` gets the job done. You could refactor it into a LINQ query, apply `ToList()` to it and pass a lambda to the `ForEach()` method of the resulting list, but the end result will probably perform the same and only be less readable. — Frédéric Hamidi, Jan 13 '12 at 10:30
LINQ may hide the loop a little bit but would certainly not eliminate it. — Serge Wautier, Jan 13 '12 at 10:30

score 3 · Accepted Answer · answered Jan 13 '12 at 10:31

Linq is intended to select a subset of data not just iterate over a collection. In your example you are not selecting anything, you are simply looping through a collection. Linq is not the correct tool for what you are trying to achieve.

Regarding your comment that Linq is faster, a linq query will eventually boil down to a series of for and if statements once the compiler has worked its magic, so I doubt it would be any faster than you foreach even if you could use it without a select clause.

score 1 · Answer 2 · answered Jan 13 '12 at 10:23

1

I found the 101 LINQ Samples guide on MSDN very useful when learning LINQ.

Have a look at the examples and have a go at re-writing the above query yourself - it's the only way to learn.

answered Jan 13 '12 at 10:23

The Ed R

316
2
6

score 1 · Answer 3 · answered Jan 13 '12 at 10:43

Since you asked for it, find it below:

foreach (RepeaterItem ri in from RepeaterItem ri in rptNews.Items let hdnUserId = (HiddenField)ri.FindControl("hdnId") let userId = Users.Current.UserId where Convert.ToInt32(hdnUserId.Value) != userId select ri)
            {
                ((ImageButton)ri.FindControl("img1")).Visible = false; 
                ((ImageButton)ri.FindControl("img2")).Visible = false;
            }

Convert foreach loop with repeater in linq

3 Answers3