How to fix view model for partial view - asp.net-mvc

Question

I've problem with creating new record to empty tables on SQLServer
When trying to pass new record I get 'Object reference not set to an instance of an object.' error
When I try edit existing record, tables display content properly, but save changes won't work. With Guests table it will only reload old entry without changes, and for Contacts it's returning same error as on creating new record.
App should let create and edit record by displaying as partial view editor forms for each table.
I'm beginner in MVC.
Below is my code.
Tables models:
[Table("GuestsTest")]
public class Guest
{
[Key]
[HiddenInput(DisplayValue = false)]
public int GuestID { get; set; }
public string GuestLastName { get; set; }
public string GuestFirstName { get; set; }
public string GuestMiddleName { get; set; }
public string GuestEmail { get; set; }
public string GuestSex { get; set; }
}
[Table("ContactsTest")]
public class Contact
{
[Key]
[HiddenInput(DisplayValue = false)]
public int ContactID { get; set; }
[HiddenInput(DisplayValue = false)]
public int GuestID { get; set; }
public int PostalCode { get; set; }
public string City { get; set; }
public string Street { get; set; }
public string HouseNumber { get; set; }
public string PhoneNumber { get; set; }
My view model
public class TableViewModel
{
public Guest GetGuest { get; set; }
public Contact GetContact { get; set; }
}
My controllers
public class AdminController : Controller
{
private IGuestRepository guestRepository;
private IContactRepository contactRepository;
private IQRCodeRepository qrcodeRepository;
public AdminController(IGuestRepository repoG, IContactRepository repoC, IQRCodeRepository repoQ)
{
guestRepository = repoG;
contactRepository = repoC;
qrcodeRepository = repoQ;
}
public ActionResult Index()
{
return View(guestRepository.Guests);
}
public ActionResult EditGuest(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
TableViewModel viewModel = new TableViewModel();
viewModel.GetGuest = guestRepository.Guests.FirstOrDefault(g => g.GuestID == id);
viewModel.GetContact = contactRepository.Contacts.FirstOrDefault(c => c.ContactID == id);
if (viewModel.GetGuest == null)
{
return HttpNotFound();
}
return View(viewModel);
}
public ActionResult GuestForm(int? id)
{
var viewModel = new TableViewModel();
viewModel.GetGuest = guestRepository.Guests.FirstOrDefault(g => g.GuestID == id);
return PartialView("_GuestForm", viewModel.GetGuest);
}
[HttpPost]
public ActionResult GuestForm(TableViewModel getGuest)
{
if (ModelState.IsValid)
{
guestRepository.SaveGuest(getGuest.GetGuest);
qrcodeRepository.CreateQRCode(getGuest.GetGuest);
TempData["message"] = string.Format("Zapisano {0} {1}", getGuest.GetGuest.GuestFirstName, getGuest.GetGuest.GuestLastName);
return RedirectToAction("EditGuest/" + getGuest.GetGuest.GuestID);
}
else
{
return PartialView(getGuest.GetGuest);
}
}
public ActionResult ContactForm(int? id)
{
var viewModel = new TableViewModel();
viewModel.GetContact = contactRepository.Contacts.FirstOrDefault(c => c.ContactID == id);
return PartialView("_ContactForm", viewModel.GetContact);
}
[HttpPost]
public ActionResult ContactForm(TableViewModel getGuest)
{
if (ModelState.IsValid)
{
contactRepository.SaveContact(getGuest.GetContact);
TempData["message"] = string.Format("Zapisano {0} {1}", getGuest.GetGuest.GuestFirstName, getGuest.GetGuest.GuestLastName);
return RedirectToAction("EditGuest/" + getGuest.GetGuest.GuestID);
}
else
{
return PartialView(getGuest.GetContact);
}
}
public ActionResult Create()
{
return View("EditGuest", new TableViewModel());
}
My view
#model MSConference.WebUI.Models.TableViewModel
#{
if (Model.GetGuest.GuestEmail == null)
{
ViewBag.Title = "Tworzenie nowego użytkownika";
}
else
{
ViewBag.Title = "Edycja";
}
Layout = "~/Views/Shared/_AdminLayout.cshtml";
}
#if (Model.GetGuest.GuestEmail == null)
{
<h2>Tworzenie nowego użytkownika</h2>
}
else
{
<h2>Edycja - #Model.GetGuest.GuestFirstName #Model.GetGuest.GuestLastName</h2>
}
#using (Html.BeginForm("EditGuest", "Admin"))
{
#Html.AntiForgeryToken()
<div class="container">
<ul class="nav nav-pills">
<li class="active"><a data-toggle="pill" href="#EditGuest">Edycja - Gość</a></li>
<li><a data-toggle="pill" href="#EditContact">Edycja - Kontakt</a></li>
<li><a data-toggle="pill" href="#EditBill">Edycja - Rezerwacja</a></li>
<li><a data-toggle="pill" href="#EditPlan">Edycja - Konferencja</a></li>
</ul>
<div class="tab-content">
<div id="EditGuest" class="tab-pane fade in active">#Html.Partial("_GuestForm", new MSConference.WebUI.Models.TableViewModel())</div>
<div id="EditContact" class="tab-pane fade">#Html.Partial("_ContactForm", new MSConference.WebUI.Models.TableViewModel())</div>
<div id="EditBill" class="tab-pane fade">sgdg</div>
<div id="EditPlan" class="tab-pane fade">gsdgsgsgsg</div>
</div>
</div>
}
<div>
#Html.ActionLink("Powrót do Listy", "Index", null, new { #class = "btn btn-success" })
</div>
I tried every method of passing model I could find and understand
EDIT
Here are my Repositories. Create error comes from if (contact.ContactID == 0)
public class EFGuestRepository : IGuestRepository
{
private EfDbContext context = new EfDbContext();
public IEnumerable<Guest> Guests
{
get { return context.Guests; }
}
public void SaveGuest(Guest guest)
{
if (guest.GuestID == 0)
{
context.Guests.Add(guest);
}
else
{
Guest dbEntry = context.Guests.Find(guest.GuestID);
if (dbEntry != null)
{
dbEntry.GuestLastName = guest.GuestLastName;
dbEntry.GuestFirstName = guest.GuestFirstName;
dbEntry.GuestMiddleName = guest.GuestMiddleName;
dbEntry.GuestEmail = guest.GuestEmail;
dbEntry.GuestSex = guest.GuestSex;
}
}
context.SaveChanges();
}
public Guest DeleteGuest(int guestId)
{
Guest dbEntry = context.Guests.Find(guestId);
if (dbEntry != null)
{
context.Guests.Remove(dbEntry);
context.SaveChanges();
}
return dbEntry;
}
}
public class EFContactRepository : IContactRepository
{
private EfDbContext context = new EfDbContext();
public IEnumerable<Contact> Contacts
{
get { return context.Contacts; }
}
public void SaveContact(Contact contact)
{
if (contact.ContactID == 0)
{
contact.GuestID = contact.ContactID;
context.Contacts.Add(contact);
}
else
{
Contact dbEntry = context.Contacts.Find(contact.ContactID);
if (dbEntry != null)
{
contact.GuestID = contact.ContactID;
dbEntry.PostalCode = contact.PostalCode;
dbEntry.City = contact.City;
dbEntry.Street = contact.Street;
dbEntry.HouseNumber = contact.HouseNumber;
dbEntry.PhoneNumber = contact.PhoneNumber;
}
}
context.SaveChanges();
}
public Contact DeleteContact(int guestId)
{
Contact dbEntry = context.Contacts.Find(guestId);
if (dbEntry != null)
{
context.Contacts.Remove(dbEntry);
context.SaveChanges();
}
return dbEntry;
}
public interface IGuestRepository
{
IEnumerable<Guest> Guests { get; }
void SaveGuest(Guest guest);
Guest DeleteGuest(int guestId);
}
public interface IContactRepository
{
IEnumerable<Contact> Contacts { get; }
void SaveContact(Contact guest);
Contact DeleteContact(int guestId);
}
I've built whole project working with Adam Freeman pro asp.net mvc 5 book (SportsStore project).

Answer 1

Passing entities to the view isn't a good practice, and depending on what you do with them when they are returned from the view, this can expose you to data tampering. Your "TableViewModel" should just consist of the flattened fields from the guest and contact, or a GuestViewModel and ContactViewModel revealing only the keys and details you need to display/edit. Entities are designed to be associated to a DbContext. Putting a reference to them in a view model is orphaning them. When you pass them back to the controller, they become just POCO instances that are deserialized from the JSON data coming from the view. They have no change tracking etc. that you might expect from using entities while they're freshly loaded from a DbContext. You can attach them to a DbContext, but you would have to manually set the entity State to "Modified" otherwise the context does not know the entity has been changed.
Your issue as it stands right now will probably be in what your SaveGuest method is doing.
The typical MVC lifecycle for the data would be roughly:
View:
Load entity(ies) from context
Populate view models
Pass to view.
Update:
Validate view model against current session
Load entity(ies) from context based on keys
Check that view model isn't stale (last mod date / timestamp / row version matches)
Validate and copy across only details that can be updated from view model into entity
SaveChanges.
Chances are if you're not seeing changes, you're probably attaching the entity to the new context without setting the entity State to "Modified". Note that this is not recommended as you are unconditionally trusting the data coming from the client. For instance you may intend to only see that a user has modified data that you created controls for, but by attaching the entity, you leave the door open for the POST call to be intercepted or played back with any/all data on the entity being altered. You would need to load the existing entity anyways to validate that nothing that shouldn't have been changed had been changed. Another possibility is you could be reloading the entity without realizing, not copying the values across from your view model's entity before calling SaveChanges, or adding the entity to the context thinking it would update the existing row, but it is saving a completely new row with new PK.

Answer 2

I solved my problem by replacing
#Html.Partial("PartialView", Model)
With
#{ Html.RenderPartial("PartialView", Model);}
I also rebuilded my models
Now my entity models looks like this:
[Table("GuestsTest")]
public class Guest
{
[Key]
public int GuestID { get; set; }
public string GuestLastName { get; set; }
public string GuestFirstName { get; set; }
public string GuestMiddleName { get; set; }
public string GuestEmail { get; set; }
public string GuestSex { get; set; }
[Required]
public virtual Contact Address { get; set; }
}
[Table("ContactsTest")]
public class Contact
{
public int ContactID { get; set; }
[Key, ForeignKey("Guest")]
public int GuestID { get; set; }
public int PostalCode { get; set; }
public string City { get; set; }
public string Street { get; set; }
public string HouseNumber { get; set; }
public string PhoneNumber { get; set; }
public virtual Guest Guest { get; set; }
}
And my view models got full rebuild to this:
public class TableViewModel
{
public GuestViewModel GetGuest { get; set; }
public ContactViewModel GetContact { get; set; }
}
public class GuestViewModel
{
[Key]
[HiddenInput(DisplayValue = false)]
public int? GuestID { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "Proszę podać nazwisko.")]
[Display(Name = "Nazwisko")]
public string GuestLastName { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "Proszę podać imię.")]
[Display(Name = "Imię")]
public string GuestFirstName { get; set; }
[MaxLength(50)]
[Display(Name = "Drugie imię")]
public string GuestMiddleName { get; set; }
[MaxLength(50)]
[Required(ErrorMessage = "Proszę podać adres email.")]
[RegularExpression(".+\\#.+\\..+", ErrorMessage = "Proszę podać prawidłowy adres e-mail.")]
[Display(Name = "Email")]
public string GuestEmail { get; set; }
[MaxLength(1)]
[Required(ErrorMessage = "Proszę podać płeć.")]
public string GuestSex { get; set; }
}
public class ContactViewModel
{
[HiddenInput(DisplayValue = false)]
public int ContactID { get; set; }
[Key, ForeignKey("Guest")]
[HiddenInput(DisplayValue = false)]
public int GuestID { get; set; }
[Required(ErrorMessage = "Proszę podać kod pocztowy.")]
[Display(Name = "Kod pocztowy")]
public int PostalCode { get; set; }
[Required(ErrorMessage = "Proszę podać Miejscowość.")]
[Display(Name = "Miejscowość")]
public string City { get; set; }
[Required(ErrorMessage = "Proszę podać ulicę.")]
[Display(Name = "Ulica")]
public string Street { get; set; }
[Required(ErrorMessage = "Proszę podać numer domu/mieszkania.")]
[Display(Name = "Numer domu/mieszkania")]
public string HouseNumber { get; set; }
[Required(ErrorMessage = "Proszę podać numer telefonu.")]
[Display(Name = "Numer telefonu")]
public string PhoneNumber { get; set; }
}
Last, I overloaded my save function to work with new models