// Entity Framework Extensions

// Doc: https://entityframework-extensions.net/merge-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();

        }

        GenerateData();

        // MergeKeepIdentity: Gets or sets if the source identity value should be preserved on `Merge`. When not specified, identity values are assigned by the destination.

        using (var context = new EntityContext())

        {

            var list = context.Customers.ToList();

            list.ForEach(x => x.Name += "_Merged" );

            list.ForEach(x => x.IdentityInt += 100 );

            list.Add( new Customer() { CustomerID = 3, IdentityInt = 4, Name ="Customer_C" });

​

            context.BulkMerge(list, options => options.MergeKeepIdentity = true);

        }

        using (var context = new EntityContext())

        {

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

        }

    }

    public static void GenerateData()

    {

        using (var context = new EntityContext())

        {

            context.Customers.Add(new Customer() { CustomerID = 1, Name ="Customer_A"});

            context.Customers.Add(new Customer() { CustomerID = 2, Name ="Customer_B"});

​

            context.BulkSaveChanges();  

        }

        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; }

    }

}