// Entity Framework Extensions

// Doc: https://entityframework-extensions.net/bulk-savechanges

​

// @nuget: Microsoft.EntityFrameworkCore.SqlServer

// @nuget: Z.EntityFramework.Extensions.EFCore

​

using Microsoft.EntityFrameworkCore;

using System;

using System.Collections.Generic;

using System.Linq;

using Microsoft.Data.SqlClient;

using System.ComponentModel.DataAnnotations;

public class Program

{

    public static void Main()

    {

        using (var context = new EntityContext())

        {

            context.Database.EnsureCreated();

        }

        using (var context = new EntityContext())

        {

            var students = new List<Student>();

            var schools = new List<School>();

            var registrations = new List<Registration>();

            var student1 = new Student() { FirstName = "Go_To_School_A"};

            var student2 = new Student() { FirstName = "Go_To_School_B"};

            var student3 = new Student() { FirstName = "Go_To_School_A_B"};

            var school1 = new School() { Name = "School_A"};

            var school2 = new School() { Name = "School_B"};

            students.Add(student1);

            students.Add(student2);

            students.Add(student3);

            schools.Add(school1);

            schools.Add(school2);

            registrations.Add(new Registration() { School = school1, Student = student1 });

            registrations.Add(new Registration() { School = school2, Student = student2 });

            registrations.Add(new Registration() { School = school1, Student = student3 });

            registrations.Add(new Registration() { School = school2, Student = student3 });

            context.BulkMerge(students);

            context.BulkMerge(schools);

            registrations.ForEach(x => {

                x.SchoolId = x.School.SchoolId;

                x.StudentId = x.Student.StudentId;

            });

            context.BulkMerge(registrations, options => {

                options.ColumnPrimaryKeyExpression = m => new { m.SchoolId, m.StudentId };

            });

            FiddleHelper.WriteTable("1 - Students", context.Students.AsNoTracking().ToList());

            FiddleHelper.WriteTable("2 - Schools", context.Schools.AsNoTracking().ToList());

            FiddleHelper.WriteTable("3 - Registrations", context.Registrations.AsNoTracking().ToList());

        }

    }

    public class EntityContext : DbContext

    {

        public EntityContext() 

        {

        }

​

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

        {

            optionsBuilder.UseSqlServer(new SqlConnection(FiddleHelper.GetConnectionStringSqlServer()));

​

            base.OnConfiguring(optionsBuilder);

        }

        public DbSet<School> Schools { get; set; }

        public DbSet<Student> Students { get; set; }

        public DbSet<Registration> Registrations { get; set; }

    }

​

    public class Registration

    {

           [Key]

           public int RegistrationId { get; set; }

           public DateTime StartDate { get; set; }

           public DateTime EndDate { get; set; }

​

           public int StudentId { get; set; }

           public Student Student { get; set; }

​

           public int SchoolId { get; set; }

           public School School { get; set; } 

    }

​

    public class School 

    {

           [Key]

           public int SchoolId { get; set; }

           public string Name { get; set; }

           public string Email { get; set; }

           public int SchoolIdentifier { get; set; } 

    }

​

    public class Student

    {

           [Key]

           public int StudentId { get; set; }

​

           public string FirstName { get; set; }

           public string LastName { get; set; }

           public string StudentIdentifier { get; set; } 

    }

}