// Entity Framework Extensions

// Doc: https://entityframework-extensions.net/insert-keep-identity

​

// @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();

        }

        List<Customer> list =  new List<Customer>() 

        {

            new Customer() { CustomerID = 1, IdentityInt = 3, Name ="Customer_A" }, 

            new Customer() { CustomerID = 2, IdentityInt = 2, Name ="Customer_B" }, 

            new Customer() { CustomerID = 3, IdentityInt = 4, Name ="Customer_C" }

        };

        // InsertKeepIdentity: Gets or sets if the source identity value should be preserved on Insert. 

        // When not specified, identity values are assigned by the destination.

        using (var context = new EntityContext())

        {

            context.BulkInsert(list, options => options.InsertKeepIdentity = true);

        }

        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; }

    }

}