// Entity Framework Plus

// Doc: https://entityframework-plus.net/query-future

​

// @nuget: EntityFramework

// @nuget: Z.EntityFramework.Plus.EF6

​

using System;

using System.Linq;

using System.Data.Entity;

using System.Collections.Generic;

using Z.EntityFramework.Plus;

​

public class Program

{

    public static void Main()

    {

        GenerateData();

        using (var context = new EntityContext())

        {

            // CREATE a pending list of future queries

            var futureCountries = context.Countries.Where(x => x.IsActive).Future();

            var futureStates = context.States.Where(x => x.IsActive).Future();

​

            // TRIGGER all pending queries in one database round trip

            // SELECT * FROM Country WHERE IsActive = true;

            // SELECT * FROM State WHERE IsActive = true

            var countries = futureCountries.ToList();

​

            // futureStates is already resolved and contains the result

            var states = futureStates.ToList();

​

            FiddleHelper.WriteTable("After Filtering", states);

        }

    }

​

    public static void GenerateData()

    {

​

        using (var context = new EntityContext())

        {

            context.Countries.Add(new Country() { Name = "US", IsActive = true });

            context.Countries.Add(new Country() { Name = "Canada", IsActive = true });

            context.Countries.Add(new Country() { Name = "Germany", IsActive = true });

            context.SaveChanges();

​

            context.States.Add(new State() { Name = "Alaska", IsActive = false, CountryId = 1 });

            context.States.Add(new State() { Name = "Alberta", IsActive = true, CountryId = 2 });

            context.States.Add(new State() { Name = "Berlin", IsActive = true, CountryId = 3 });

            context.States.Add(new State() { Name = "Quebec", IsActive = true, CountryId = 2 });

            context.States.Add(new State() { Name = "Hamburg", IsActive = false, CountryId = 3 });

            context.States.Add(new State() { Name = "New Jersey", IsActive = true, CountryId = 1 });

​

            context.SaveChanges();

        }

​

    }

​

    public class EntityContext : DbContext

    {

        public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())

        {

​

        }

        public DbSet<Country> Countries { get; set; }

        public DbSet<State> States { get; set; }

    }

​

    public class Country

    {

        public int CountryId { get; set; }

        public string Name { get; set; }

        public bool IsActive { get; set; }

        public List<State> States { get; set; }

    }

​

    public class State

    {

        public int StateId { get; set; }

        public string Name { get; set; }

        public bool IsActive { get; set; }

        public int CountryId { get; set; }

    }

}