Фильтры таблиц Entity Framework Core (если таблица используется более чем один раз)

На самом деле вы можете обойти эту «схему», создав иерархию наследования TPH в EF Core. например:

using Microsoft.EntityFrameworkCore;
using System;
using System.Data;
using System.Linq;

namespace EfCoreTest
{

    public abstract class Lookup
    {
        public int LookupID { get; set; }
        public int LookupTypeID { get; set; }
        public int Key { get; set; }
        public string Value { get; set; }
    }

    public class CustomerTitle : Lookup
    {

    }
    public class PetType : Lookup
    {

    }
    public class Customer
    {
        public int CustomerID { get; set; }
        public CustomerTitle CustomerTitle { get; set; }
        public int CustomerTitleID { get; set; }
        public PetType PetType { get; set; }
        public int PetTypeID { get; set; }
    }


    public class Db : DbContext
    {
        readonly string connectionString;

        public DbSet<Customer> Customers { get; set; }
        public DbSet<Lookup> Lookup { get; set; }
        public DbSet<CustomerTitle> CustomerTitles { get; set; }
        public DbSet<PetType> PetTypes { get; set; }

        public Db(): this("server=.;database=EfCoreTest;Integrated Security=true")
        {

        }
        public Db(string connectionString)
        {
            this.connectionString = connectionString;
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(connectionString);
            base.OnConfiguring(optionsBuilder);
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Lookup>()
                .HasAlternateKey(e => new { e.LookupTypeID, e.Key });

            modelBuilder.Entity<Lookup>()
                .HasDiscriminator(e => e.LookupTypeID);

            modelBuilder.Entity<CustomerTitle>()
                .HasDiscriminator()
                .HasValue(1);
            modelBuilder.Entity<PetType>()
                .HasDiscriminator()
                .HasValue(2);

            var fks = from et in modelBuilder.Model.GetEntityTypes()
                      from fk in et.GetForeignKeys()
                      where typeof(Lookup).IsAssignableFrom(fk.PrincipalEntityType.ClrType)
                      select fk;
            foreach (var fk in fks)
            {
                fk.DeleteBehavior = DeleteBehavior.Restrict;
            }

            base.OnModelCreating(modelBuilder);
        }
    }



    class Program
    {
        static void Main(string[] args)
        {


            using (var db = new Db())
            {
                db.Database.EnsureDeleted();
                db.Database.EnsureCreated();

                var Mr = new CustomerTitle() { Key = 1, Value = "Mr" };
                var Mrs = new CustomerTitle() { Key = 2, Value = "Mrs" };
                var Miss = new CustomerTitle() { Key = 3, Value = "Miss" };
                db.CustomerTitles.AddRange( new []{ Mr,Mrs,Miss});

                var Dog = new PetType() { Key = 1, Value = "Dog" };
                var Cat = new PetType() { Key = 2, Value = "Cat" };
                var Hamster = new PetType() { Key = 3, Value = "Hamster" };
                db.PetTypes.AddRange(new[] { Dog,Cat,Hamster });

                db.SaveChanges();
            }

            using (var db = new Db())
            {
                var titles = db.CustomerTitles.ToDictionary(t => t.Value);
                var petTypes = db.PetTypes.ToDictionary(t => t.Value);

                var cust = new Customer();
                cust.CustomerTitle = titles["Mr"];
                cust.PetType = petTypes["Hamster"];

                db.SaveChanges();
            }


            Console.WriteLine("Hit any key to exit");
            Console.ReadKey();


        }
    }
}

В качестве альтернативы вы можете создать представления для поиска, например:

create or alter view CustomerTitle
as
select [Key] CustomerTitleId, Value
from Lookup
where LookupTypeID = 1