Find list of values for item using Linq

Question

I have a list that contains int values, I want to use linq expression to return a result where a property equals the list items values. How can I do that?

list<int> x = ...

var o = anotherList.where(s => s.Id == (the list values));

What *exactly* do you mean by "where a property equals the list items values". Do you mean where the list *contains* the property value? If so, think about what that might hint at... how can you tell whether a list contains a value? — Jon Skeet, Mar 19 '13 at 10:13

score 10 · Answer 1 · edited Mar 19 '13 at 10:14

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var o = anotherList.Where(s => list.Contains(s.ID));

edited Mar 19 '13 at 10:14

Grant Thomas

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answered Mar 19 '13 at 10:13

TalentTuner

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score 1 · Answer 2 · edited May 23 '17 at 12:24

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I translate "a property equals the list items values" with "anotherList contains this list ID":

An efficient approach is using Join:

var o = from al in anotherList
        join tlId in thelist
        on al.Id equals tlId
        select al;

edited May 23 '17 at 12:24

Community

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answered Mar 19 '13 at 10:16

Tim Schmelter

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How about if there is duplicates in `thelist` – Magnus Mar 19 '13 at 10:19
No the `join` will match the duplicates also and return them for `al`. – Magnus Mar 19 '13 at 10:25
@Magnus: That's exactly what i've said. Duplicates on the right side are omitted(like a `INNER JOIN` in sql). – Tim Schmelter Mar 19 '13 at 10:30
It'll match duplicates in _any_ of the lists. – Magnus Mar 19 '13 at 10:32
No you wont. `var anotherList = new List(){1,2,3}; var thelist = new List(){1,1,1}; var q = from x in anotherList join y in thelist on x equals y select x;` will give you three 1. – Magnus Mar 19 '13 at 10:38
You are right, i should have tested it. However, it's not clear if that is desired here. – Tim Schmelter Mar 19 '13 at 10:42

score 0 · Answer 3 · answered Mar 19 '13 at 10:14

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 var o = anotherList.Where(s =>list.Any(a=> a.Id == s.Id));

answered Mar 19 '13 at 10:14

Akrem

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score 0 · Answer 4 · answered Mar 19 '13 at 10:23

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You could also use an anonymous method:

 var o = anotherList.Where(delegate(someItem s) { return list != null && list.Contains(s.ID); });

answered Mar 19 '13 at 10:23

Mintey

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Find list of values for item using Linq

4 Answers4