// Entity Framework Extensions

// @nuget: Microsoft.EntityFrameworkCore.SqlServer

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

​

using System;

using System.Linq;

using Microsoft.EntityFrameworkCore;

using System.Collections.Generic;

using Microsoft.Data.SqlClient;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

​

public class Program

{

    public static void Main()

    {

        using (var context = new EntityContext())

        {

            context.Database.EnsureCreated();

        }

        var c = new Customer() { CustomerID = 10, IdentityInt = 3, Name ="Customer_A" };

        var c2 = new Customer() { CustomerID = 20, IdentityInt = 1, Name ="Customer_B" };

        var c3 = new Customer() { CustomerID = 20, IdentityInt = 11, Name ="Customer_C" }; // duplicate Id

        using (var context = new EntityContext())

        {

            context.Database.OpenConnection();

            try {

                context.Database.ExecuteSqlRaw("SET IDENTITY_INSERT dbo.Customers ON");

                context.Add(c);

                context.SaveChanges();

                context.Database.ExecuteSqlRaw("SET IDENTITY_INSERT dbo.Customers OFF");

            }

            finally {

                context.Database.CloseConnection();

            }

        }

        using (var context = new EntityContext())

        {

            using (var trans = context.Database.BeginTransaction()) {

                try {

                context.Database.ExecuteSqlRaw("SET IDENTITY_INSERT dbo.Customers ON");

                context.Add(c2);

                context.SaveChanges();

                context.Database.ExecuteSqlRaw("SET IDENTITY_INSERT dbo.Customers OFF");

                trans.Commit();

                }

                catch {

                    trans.Rollback();

                }

            }

        }

        using (var context = new EntityContext())

        {

            using (var trans = context.Database.BeginTransaction()) {

                try {

                context.Database.ExecuteSqlRaw("SET IDENTITY_INSERT dbo.Customers ON");

                context.Add(c3);

                context.SaveChanges();

                context.Database.ExecuteSqlRaw("SET IDENTITY_INSERT dbo.Customers OFF");

                trans.Commit();

                }

                catch (Exception ex) {

                    trans.Rollback();

                    Console.WriteLine(ex.InnerException.Message);

                }

            }

        }

        using (var context = new EntityContext())

        {

            FiddleHelper.WriteTable(context.Customers.ToList());    

        }

    }

    public class EntityContext : DbContext

    {

        public EntityContext() 

        {

        }

​

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

        {

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

​

            base.OnConfiguring(optionsBuilder);

        }

        public DbSet<Customer> Customers { get; set; }

    }

    public class Customer

    {

        [Key]

        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

        public int CustomerID { get; set; }

        public int IdentityInt { get; set; }

        public string Name { get; set; }

    }

}