Linq to Find All Childs Related to Parents Id

LINQ to find all childs related to parents ID

Usually in many to many relationships, the related EF classes have a navigation property that represents the collection of objects associated with each item.

In your sample code, you were referencing Subject.Experiences, but you were missing the piece that correlates the experience id correctly.

Something like this should do the trick, where id is the selected experience id:

var subjectList = db.Subjects
    .Where(s => s.Experiences.Any(experience => experience.Id == id))
    .ToList();

LINQ query to group parent and child elements

you can try with Recursion

public static List<LocationViewModel> GetHierarchy(List<LinkParentChildViewModel> linkParentChildViewModels, int parentId)
{
    return linkParentChildViewModels.Where(x => x.Parent.Id == parentId).Select(x => new LocationViewModel
    {
        Id = x.Parent.Id,
        Code = x.Parent.Code,
        ChildLocations = GetHierarchy(linkParentChildViewModels, x.Child.ChildLocationId)
    }).ToList();
}

Call this from Main method

var result = GetHierarchy(LinksParentChild, 8);

Combine parent list & multiple child list using LINQ

Simple go through each Department object and assign its children lists:

foreach (var dept in DepartmentList) {
    dept.StudentList = StudentList.Where(s => s.DepartmentId == dept.Id).ToList();
    dept.ProfessorList = ProfessorList.Where(p => p.DepartmentId == dept.Id).ToList();
}

Fluent LINQ - Select a list of parents that contains a list of children where a subset of children are present

You can flip your condition, and check to make sure all of the list values are contained within the Children collection:

var matches = parents.Where(p => myList.All(v => p.Children.Select(c => c.SomeValue).Contains(v)));

Linq select parent/parents record with matching child items

I think this would work for you :

var userByUserName = _applicationDbContext.Users.FirstOrDefault(x =>
                x.NormalizedUserName == userName.ToUpper() &&
                x.ClientUsers.Any(c => c.ClientId == client.Id));

Get Children common to All Parents

Since you have many-to-many relationship, it's better to base (start) the query on the resulting entity (Children), thus avoiding the need of GroupBy /Distinct if you start it from the other end (Parent).

So given

IQueryable<Parent> parents

and assuming you have access to the context, the query can be written as follows:

var query = context.Set<Children>()
    .Where(c => parents.All(p => p.ParentChildrens.Select(pc => pc.ChildrenId).Contains(c.ChildrenId)))
    .Select(c => new
    {
        Id = c.ChildrenId,
        Name = c.ChildrenLocalizations.Where(cl => cl.Language == "en").Select(cl => cl.Name).FirstOrDefault()
    });

which nicely translates to a single SQL.

You start with unique Children. For requirement (2) you simply use the navigation property. The requirement (1) is more complicated (all is always harder to achieve than any), but I think the criteria

parents.All(p => p.ParentChildrens.Select(pc => pc.ChildrenId).Contains(c.ChildrenId))

quite intuitively represents child common to all parents.

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