CODEWITHSUNDEEP
c#linq
simbada
simbada

Reputation: 980

How do i filter one list from another list using linq

I wrote the following query to filter query.

I used First() which is causing the issue I didn't notice earlier because Entity2 is also a collection. It only filters the first Id.

query = query.Where(x => filter.Ids.Contains(x.Entity2.Select(y => y.testId).First()));

Please suggest how I can use contains to check all testId property of Entity2 ?

Basically x.Entity2.Select(y => y.testId) is list of Ids which i want to check whether they contains in filter.Ids or not.

Upvotes: 0

Views: 1079

Answers (2)

Starlord Live
Starlord Live

Reputation: 79

For your above query you can also use Any() and Contains() both , it will work as According to you filter is collection which has Ids and Entity2 both are also collection , so assuming that i wrote this,

query = query.Where(x => filter.Where(a=> a.Entity2.Any(y=> a.Ids.Contains(y.testId));

but in your query also you can remove First() and can use ToList() but it will be throw OutofMemoryException , if data is large.

Upvotes: 0

steliosbl
steliosbl

Reputation: 8921

If I understand correctly, filter.Ids and x.Entity2.Select(y => y.testId) are both lists if Ids, and you want to make sure that all Ids from x.Entity2 are also in filter.Ids. In that case, you want the following:

var result = query.Where(x => x.Entity2.Count(y => filter.Ids.Contains(y.testId)) == x.Entity2.Count);

What we are doing here is we are counting for each element of query, the number of Ids that are both in it's Entity2 and in filter.Ids. If that number is equal to the total number of Ids in Entity2, then we include that in the result.

Upvotes: 1

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