Searching in a list of lists

Question

I have a list which also contains a list which contains some objects:

var elements = new List<ElementGroup>()
            {
                new ElementGroup("WIRES")
                {
                    new Element() {Name = "Wires", Image = "wires.jpg"}
                },
                new ElementGroup("GROUND")
                {
                    new Element() {Name = "Ground", Image = "ground.jpg"}
                }
            };

ElementGroup class:

public class ElementGroup : List<Element>

I want to apply Linq query to all Element objects from all ElementGroup lists but if I do it like this:

elements.Where(c => c.Family.Contains(searchText.ToUpper()));

it applies the query on ElementGroup lists.

Side note: [Why not inherit from List?](https://stackoverflow.com/questions/21692193/why-not-inherit-from-listt) — Zohar Peled, Mar 26 '18 at 14:26
First, reformat your question if possible. You want to select all elements if one of the element matches the predicate or select only which matches the predicate?. — Rudresha Parameshappa, Mar 26 '18 at 14:30
What type is `c` in your example? I don't see any class with the property `Family` — vbnet3d, Mar 26 '18 at 14:30
@vbnet3d `c` is the element of the list. Checkout linq about `Func` — Rudresha Parameshappa, Mar 26 '18 at 14:31
Don't use `ToUpper` for comparisons. Use the `StringComparison` option. You'll most likely want to use `StringComparison.InvariantCultureIgnoreCase`. — Nyerguds, Mar 26 '18 at 14:32
@RudreshaParameshappa no, it's a valid question. That `Family` must be a property of the `ElementGroup` class, but that class isn't given in the question, and none of the given code fills in such a `Family` property. — Nyerguds, Mar 26 '18 at 14:33
@Nyerguds there is no `StringComparision` parameter for `Contains` he can to use `IndexOf` with `StringComparision` — Rudresha Parameshappa, Mar 26 '18 at 14:34
Point. Still, hard to understand without knowing what type that `Family` even _is_. — Nyerguds, Mar 26 '18 at 14:35

Yogee · Answer 1 · 2018-03-26T15:12:03.140

0

//Here is how you can get List of Element from List<ElementGroup>.

List<Element> result = 
    elements.SelectMany(elementGroup =>             
        elementGroup.Where(element=>element.Name=="Wires")).ToList();

edited Mar 26 '18 at 15:12

answered Mar 26 '18 at 15:07

Yogee

1,412
14
22

PS: Sai's answer is not complete but correct, not sure why his answer is down voted. – Yogee Mar 26 '18 at 15:07

gtestasker · Answer 2 · 2018-03-26T14:51:20.123

-1

Use SelectMany which flattens the inner list.

Code might look like this elements.SelectMany(s => s.Elements)

And you can work on this list of elements

EDIT:

Also, consider having a list of Elements "in" ElementGroup rather than inheriting. Then using SelectMany becomes the natural choice.

edited Mar 26 '18 at 14:51

answered Mar 26 '18 at 14:34

gtestasker

61
7

@Ionut Gabriel Pitigoi - Any specific reason you are inheriting and not having List as a property in ElementGroup? – gtestasker Mar 26 '18 at 14:59

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