A relational store has been configured without specifying either the DbConnection or connection string to use

I using asp.net vnext and ef7 when i want adding user i getting this error:

A relational store has been configured without specifying either the DbConnection or connection string to use.

What is this?

Consider my app start:

using DomainModels;
using Microsoft.AspNet.Builder;
using Microsoft.AspNet.Hosting;
using Microsoft.AspNet.Routing;
using Microsoft.Framework.ConfigurationModel;
using Microsoft.Framework.DependencyInjection;
using Presentation.DataAccessLayer.Context;
using Microsoft.AspNet.Identity;
namespace Presentation
{
    public class Startup
    {
        public Startup(IHostingEnvironment env)
        {
            Configuration = new Configuration()
                .AddJsonFile("config.json")
                .AddEnvironmentVariables();
        }

        public IConfiguration Configuration { get; set; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddEntityFramework().AddSqlServer().AddDbContext<ApplicationContext>();
            services.AddDefaultIdentity<ApplicationContext, ApplicationUser, IdentityRole>(Configuration);
            services.AddMvc();
        }

        public void Configure(IApplicationBuilder app)
        {
            app.UseStaticFiles();
            app.UseIdentity();
            app.UseMvc(
                routes =>
                {
                    routes.MapRoute("default", "{controller}/{action}/{id?}",
                        new {controller = "Home", action = "Index"});
                });
        }
    }
}

and this is my config.json:

{
    "Data": {
        "DefaultConnection": {
            "Connectionstring": "Data Source=.\\sqlexpress;Initial Catalog=CraftCenter;Integrated Security=True;"
        }
    },
    "EntityFramework": {
        "ApplicationDbContext": {
            "ConnectionStringKey": "Data:DefaultConnection:ConnectionString"
        }
    }

}