using Microsoft.EntityFrameworkCore;

using System.Collections.Generic;

using System.Linq;

using System;

using System.ComponentModel.DataAnnotations.Schema;

​

namespace EFTest

{

    public class SomeDbObj

    {

        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

        public string Id { get; set; }

​

        public string SomeFieldA { get; set; }

        public string SomeFieldB { get; set; }

    }

​

    public class DbContext2 : DbContext

    {

        public DbContext2(){ }

​

        public DbContext2(DbContextOptions<DbContext2> options)

            : base(options){ }

​

        public DbSet<SomeDbObj> DbObjs { get; set; }

    }

​

    class Program

    {

        static void Main(string[] args)

        {

            var options = new DbContextOptionsBuilder<DbContext2>()

                .UseInMemoryDatabase(databaseName: "Add_writes_to_database")

                .Options;

​

            using (var context = new DbContext2(options))

            {

                var someOtherObj = new SomeDbObj { SomeFieldA = "A2" , SomeFieldB = "B2" };

​

                var efTrackedThing = context.DbObjs.Add(new SomeDbObj { SomeFieldA = "A1" , SomeFieldB = "B1" });

                someOtherObj.Id = efTrackedThing.Entity.Id;

                try { 

                    context.DbObjs.Update(someOtherObj);

                } catch (System.InvalidOperationException e) {

                    System.Console.WriteLine ("Attempt 1: Got exception on re-use: " + e.Message.Substring(50));

                }

                context.ChangeTracker.Clear();

                context.DbObjs.Update(someOtherObj);

                System.Console.WriteLine ("Attempt 2, after clearing change tracker. No Exception");

            }

        }

    }

​

}