EF7 rc1-final: Error updateing entities

I am creating an API using ASP.NET5 and recently updated completly to Entity Framework rc1-final, and when I try to execute, I get sometimes this Exception and sometimes the same code just works:

The instance of entity type ‘Asp5ApiSD.Models.Addon’ cannot be tracked because another instance of this type with the same key is already being tracked.

This should be the relative parts of my code:

    public class BCContext : DbContext
    {
        private readonly IConfiguration _config;
        public BCContext (DbContextOptions options)
: base(options)
        {
        }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            builder.Entity<Addon>(e =>
            {
                e.Property(c => c.IDaddon).ValueGeneratedOnAdd();
                e.HasKey(c => c.IDaddon);

            });

            base.OnModelCreating(builder);
        }
        public virtual DbSet<Addon> Addons { get; set; }
    }

    public interface IAddonRepository
    {
        List<Addon> SelectAll();
        Addon SelectByID(string id);
        void Insert(Addon obj);
        void Update(Addon obj);
        void Delete(string id);
    }
    public class AddonRepository : IAddonRepository
    {
        public BCContext Context { get; private set; }
        public AddonRepository(BCContext context)
        {
            this.Context = context;
        }

        public List<Addon> SelectAll()
        {
            return Context.Addons.ToList();
        }

        public Addon SelectByID(string id)
        {
            return Context.Addons.Where(i =>
                   i.IDaddon == Int32.Parse(id)).SingleOrDefault();
        }

        public void Insert(Addon obj)
        {
            Context.Entry(obj).State = EntityState.Added;
            Context.SaveChanges();
        }

        public void Update(Addon obj)
        {
            Context.Entry(obj).State = EntityState.Modified;
            Context.SaveChanges();
        }

        public void Delete(string id)
        {
            Addon obj = Context.Addons.SingleOrDefault(i => i.IDaddon == Int32.Parse(id));
            Context.Entry(obj).State = EntityState.Deleted;
            Context.SaveChanges();
        }
    }

    [Route("api/[controller]")]
    public class AddonController : Microsoft.AspNet.Mvc.Controller
    {
        public IAddonRepository _Repository { get; set; }

        public AddonController(IAddonRepository context)
        {
            _Repository = context;
            if (_Repository.SelectAll().Count != _addons.Count)
                _addons.AddRange(_Repository.SelectAll());
        }

        [HttpPost("{id}", Name = "SetAddonById")]
        public IActionResult UpdateItem(int id, [FromBody] Addon item)
        {
            if (item == null)
            {
                return HttpNotFound();
            }

            if (ModelState.IsValid)
            {
                _Repository.Update(item);
            }
            return new HttpStatusCodeResult(204); // 201 No Content
        }

    }

    public class Startup
    {

        public Startup(IHostingEnvironment env, IApplicationEnvironment appEnv)
        {
            // Setup configuration sources.
            var builder = new ConfigurationBuilder()
                .SetBasePath(appEnv.ApplicationBasePath)
                .AddJsonFile("config.json")
                .AddEnvironmentVariables();
            Configuration = builder.Build();
        }

        public IConfiguration Configuration { get; set; }

        // For more information on how to configure your application, visit http://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddEntityFramework()
                    .AddSqlServer()
                    .AddDbContext<BCContext>(options => options.UseSqlServer(Configuration.Get<string>("Data:ConnectionString")));

            services.AddScoped<IAddonRepository, AddonRepository>();

        }

        public void Configure(IApplicationBuilder app)
        {
            app.UseMvc();
            app.UseWelcomePage();

            app.UseExceptionHandler("/Home/Error");
        }
    }

    [Table("Addon")]
    public class Addon
    {
        [Key]
        public int IDaddon { get; set; }
        public string Description { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }

The interessting thing is that sometimes I can’t update a single item and then I can make 10 upgrades behind each other. The code did also not work on Beta-8, I tought maybe a update to last version would solve it.

[rowanmiller]

The idea was to “cache” the data to memory for performance reason.

The code has actually hurt perf quite a bit (and introduced thread-safety issues). A new instance of the controller is created for every request, so your call to _Repository.SelectAll() in the constructor is fetching every row from the database for every request, even though most of your actions probably only need one (or even zero) rows from the database. I would remove it.

BTW, because your repository is setup to not assume that an entity being passed to Update was already fetched from the same repository instance (and is therefore not tracked), you can also add AsNoTracking() to your queries. That will resolve your issue with the exception.

[sepei]

Thank you. I imagine the question why it worked from time to time. But solved and it can be closed. Sorry thought there was a problem on the framework.