using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using Newtonsoft.Json;

​

namespace ConsoleApp16

{

    public class Program

    {

        public static void Main(string[] args)

        {

           List<Semester> s = new List<Semester>();

            /* Semester{1,{}}

                Semester{2,{}}

                 Semester{3,{1,2}}

                 Semester{4,{1}}

                Semester{5,{2,4}} */

            s.Add(new Semester { Id = 1, Parents = new List<SemesterParent>() });

            s.Add(new Semester { Id = 2, Parents = new List<SemesterParent>() });

            s.Add(new Semester { Id = 3, Parents = new List<SemesterParent> { new SemesterParent { Id = 1 }, new SemesterParent { Id = 2 } } });

            s.Add(new Semester { Id = 4, Parents = new List<SemesterParent> { new SemesterParent { Id = 1 } } });

            s.Add(new Semester { Id = 5, Parents = new List<SemesterParent> { new SemesterParent { Id = 2 }, new SemesterParent { Id = 4 } } });

            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();

            Console.WriteLine(JsonConvert.SerializeObject(result));

        }

    }

    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;}

    }

}