Linq select one id with flattened list (example)

If you have an object with an id property and another property with a list of objects (has inheritance) and wants to get a new list with the inherited list flattened and keep the id. You can do like this:

public class Test { private void TestMethod() {


            Category _cat1 = new Category();

            _cat1.Color = "Blue";
            Category _cat2 = new Category();

            _cat2.Color = "Green";
            Category _cat3 = new Category();

            _cat3.Color = "Red";
            Category _cat4 = new Category();

            _cat4.Color = "Yellow";
            Category _cat5 = new Category();

            _cat5.Color = "Lime";
            List list1 = new List();

            list1.Add(_cat1);

            list1.Add(_cat2);

            list1.Add(_cat3);
            List list2 = new List();

            list2.Add(_cat4);

            list2.Add(_cat5);
            List _listCar = new List();

            _listCar.Add(new Car() { Id = 1, Categories = list1 });

            _listCar.Add(new Car() { Id = 2, Categories = list2 });
            var item = (from x in _listCar

                        .SelectMany(x => x.Categories, (Ids, Cars) =>

            new { Ids, Cars })

                        select new

                        {

                            Id = x.Ids.Id,

                            Cat = x.Cars.Color

                        }).ToList();
            var aba = item;
        }

    }

    public class Car

    {

        public int Id { get; set; }

        public List Categories { get; set; }

} public class Category { public string Color { get; set; } } }

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