Error when try to add new fields in ASP.NET Identity

Hi Guys,

in my ASP.NET MVC5 application, I'm customizing profile information in ASP.NET Identity by following the tutorial written by Pranav Rastogi. According to this I modified:

1) Models\IdentityModels,cs by adding three new properties:

    public class ApplicationUser : IdentityUser
    {
        public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
        {
            // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
            var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
            // Add custom user claims here
            return userIdentity;
        }

        public string FirstName { get; set; }
        public string MiddleName { get; set; }
        public string LastName { get; set; }
    }

2) Models\AccountViewModels.cs by adding these three new fields

    public class RegisterViewModel
    {
        /*--------------------------------------------- Added by Phil 2015-03-12 /*---------------------------------------------*/
        [Required(ErrorMessage = "First name is required")]
        [StringLength(20, ErrorMessage="The first name must be shorter than 20 characters.")]
        [Display(Name="First name")]
        public string FirstName { get; set; }

        [StringLength(20, ErrorMessage = "The middle name must be shorter than 20 characters.")]
        [Display(Name = "Middle name")]
        public string MiddleName { get; set; }

        [Required(ErrorMessage = "Last name is required")]
        [StringLength(50, ErrorMessage = "The last name must be shorter than 50 characters.")]
        [Display(Name = "Middle name")]
        public string LastName { get; set; }
        /*------------------------------------------------------------------------------------------------------------------------------------*/

        [Required(ErrorMessage = "Email is required")]
        [EmailAddress(ErrorMessage = "This is not a valid email address")]
        [Display(Name = "Email")]
        public string Email { get; set; }

        [Required(ErrorMessage = "Password is required")]
        //[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
        [StringLength(100, ErrorMessage = "The password must be at least {2} characters long.", MinimumLength = 8)]
        [DataType(DataType.Password)]
        [Display(Name = "Password")]
        public string Password { get; set; }

        [DataType(DataType.Password)]
        [Display(Name = "Confirm password")]
        [Compare("Password", ErrorMessage = "The password and confirmation password do not match.")]
        public string ConfirmPassword { get; set; }
    }

3) Controllers\AccountController.cs, Register action, in order to store those new fields

        // POST: /Account/Register
        [HttpPost]
        [AllowAnonymous]
        [ValidateAntiForgeryToken]
        public async Task<ActionResult> Register(RegisterViewModel model)
        {
            if (ModelState.IsValid)
            {
                var user = new ApplicationUser { FirstName = model.FirstName, MiddleName = model.MiddleName, LastName = model.LastName, UserName = model.Email, Email = model.Email};
                var result = await UserManager.CreateAsync(user, model.Password);
                if (result.Succeeded)

However, after rebuild application and despite running migration and update of the db, an error occur when try to register a new user:

The model backing the 'ApplicationDbContext' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269). 
  Descrizione: Eccezione non gestita durante l'esecuzione della richiesta Web corrente. Per ulteriori informazioni sull'errore e sul suo punto di origine nel codice, vedere la traccia dello stack. 

 Dettagli eccezione: System.InvalidOperationException: The model backing the 'ApplicationDbContext' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269).

Errore nel codice sorgente: 



Riga 153:            {
Riga 154:                var user = new ApplicationUser { FirstName = model.FirstName, MiddleName = model.MiddleName, LastName = model.LastName, UserName = model.Email, Email = model.Email};
Riga 155:                var result = await UserManager.CreateAsync(user, model.Password);
Riga 156:                if (result.Succeeded)
Riga 157:                {
 

Thanks in advance for your help.

Phil