Adding to two different lists from one LINQ query

Question

I have two Lists (call them foo and bar) and I want to minimise the number of LINQ queries (okay, I know they have a minimal overhead, but still, two queries takes twice the time and LINQ with iOS development can be problematic). The query will be exactly the same, but I want to add the results to the two lists.

My current code looks like this

List<foo> foos = new List<foos>();
List<bar> bars = new List<bars>();

var agg = (from fa in mainList
           from pa in fa.subList
           from cg in pa.subSubList
           let cr = pa.anotherSubList
           where cg.DatePerformed.Year == DateTime.Now.Year - 1 && cr.Count != 0
           select foos.Add(fa)
           select bars.Add(pa));

The compiler is complaining at the second select.

Is there a way to do what I want to do in LINQ or am I going to need to use two loops?

i3arnon · Accepted Answer · 2014-01-02 18:29:31Z

1

You can select both items and iterate over the results to add one item to the first list and the other to the other list. You can do that with a class that can hold both items, a Tuple or just an anonymous type like this:

var result = from fa in mainList
    from pa in fa.subList
    from cg in pa.subSubList
    let cr = pa.anotherSubList
    where cg.DatePerformed.Year == DateTime.Now.Year - 1 && cr.Count != 0
    select new {First=fa, Second=pa};
foreach (var pair in result)
{
    foos.Add(pair.fa);
    bars.Add(pair.pa);
}

edited Jan 2, 2014 at 18:29

answered Dec 28, 2013 at 12:41

i3arnon

117k33 gold badges334 silver badges358 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Nodoid Over a year ago

That's great - pity there isn't really a way to add directly to the Lists from within the query. I wonder how much of a hit having the query and the foreach would be over having the two queries. I did consider using Union, but again, doesn't quite hit what I want to do.

i3arnon Over a year ago

1. You could convert the linq to a iterative foreach statements. 2. If you measure in big O notation, it's exactly the same.

i3arnon Over a year ago

Actually, if that's linq to objects it is exactly the same, because it's built on yields.

Collectives™ on Stack Overflow

Adding to two different lists from one LINQ query

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related