using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace TestProject.NET
{
    public class Problem
    {
        public Problem()
        {
            P_A = new List<Problem_Approval>();
        }

        [Key]
        public int ID_P { get; set; }
        [Required, MaxLength(1000)]
        public string Name { get; set; }
        public int Chance { get; set; }
        public int Chance_Real { get; set; }

        public virtual List<Problem_Approval> P_A { get; set; }
    }

    public class Approval
    {
        public Approval()
        {
            P_A = new List<Problem_Approval>();
        }

        [Key]
        public int ID_A { get; set; }
        [Required, MaxLength(1000)]
        public string Name { get; set; }
        public int Chance { get; set; }
        public int Type { get; set; }

        public virtual List<Problem_Approval> P_A { get; set; }
    }

    public class Problem_Approval
    {
        [Key]
        public int ID { get; set; }
        [Required]
        public int ID_P { get; set; }
        [Required]
        public int ID_A { get; set; }

        [ForeignKey("ID_P")]
        public virtual Problem Problem { get; set; }
        [ForeignKey("ID_A")]
        public virtual Approval Approval { get; set; }
    }

    public class MyContext : DbContext
    {
        public MyContext() : base("MyContext") { }

        public DbSet<Problem> Problems { get; set; }
        public DbSet<Approval> Approvals { get; set; }
        public DbSet<Problem_Approval> Problems_Approvals { get; set; }
    }
}

            using (var db1 = new MyContext())
            {
                var q1 = from p in db1.Problems
                        where p.ID_P == 1
                        from a in db1.Approvals
                        where a.ID_A < 3
                        join j in db1.Problems_Approvals
                        on new { p.ID_P, a.ID_A }
                        equals new { j.ID_P, j.ID_A }
                        into res
                        from r in res
                        select a;
                q1.Load();
                dataGridView1.DataSource = db1.Approvals.Local.ToBindingList();
            }