LINQ select List where sub-list all items contains another list

Question

I have a model with list items.

public class Semester{
    public int Id { get; set; }
    public List<SemesterParent> Parents { get; set; }
}

public class SemesterParent{
    public int Id { get; set; }
    public int SemesterId { get; set; }
    public int ParentId { get; set; }
}

I have a list<int> of parentids. I want to get semester list that Parents in parentids list.

For example

Semester{1,{}}
Semester{2,{}}
Semester{3,{1,2}}
Semester{4,{1}}
Semester{5,{2,4}}

When I have ParentIdes {1,2} the result is:

Semester{3,{1,2}}
Semester{4,{1}}

I use this code.

var parentIds =
            await _semesterTermStudentService.Select(m => m.IsAccept && m.StudentId == student.Id);
var semester=await _semesterService.FindAsync(m=>
             m.Parents.Any(y => parentIds.Contains(y.ParentId)));

I agree with @SowmyadharGourishetty, there isn't an explanation on why inputs {1, 2} retrieves parentids only containing 1 but not parentids that only contain 2. — Hayden
– Hayden, Commented Aug 19, 2020 at 7:21
@Hayden, I later saw the title LINQ select List where sub-list all items contains another list it says all items that match the parentId's — Sowmyadhar Gourishetty
– Sowmyadhar Gourishetty, Commented Aug 19, 2020 at 7:23
@SowmyadharGourishetty Thanks for pointing that out, just not clear in the question itself. — Hayden
– Hayden, Commented Aug 19, 2020 at 7:24

Sowmyadhar Gourishetty · Accepted Answer · 2020-08-19 06:43:21Z

2

You can do as below. Here is the working code

List<Semester> s = new List<Semester>();
var parentIds = new List<int> { 1, 2 };
var result = s.Where(x => x.Parents != null && x.Parents.Any() && x.Parents.All(y => parentIds.Contains(y.Id))).ToList();

edited Aug 19, 2020 at 6:43

answered Aug 19, 2020 at 6:30

Sowmyadhar Gourishetty

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6 Comments

Sowmyadhar Gourishetty Over a year ago

If you want to include the list if it atleast has any one of the parentId's, you can use Any instead of All in the above Linq

ar.gorgin Over a year ago

Thanks, when i use this , find all items that contains id but i want to select items that every item list in list.

Sowmyadhar Gourishetty Over a year ago

@ar.gorgin Yes, this works in the same way. can you please check the working code attached

Sowmyadhar Gourishetty Over a year ago

You are almost there, instead of m.Parents.Any try m.Parents.All. Which I have already mentioned in my answer. please check my answer again

ar.gorgin Over a year ago

i use All , this return items like Any and item with this id.

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