ASP.NET MVC 4, Multiple model in View, System.NullReferenceException: - asp.net-mvc-4

Question

I have a problem with my App.
I have This Multiple Model:
public class MultipleModel
{
public Staff Staff;
public RegisterModel RegisterModel;
}
public class RegisterModel
{
[Required]
[Display(Name = "User name")]
public string UserName { get; set; }
[Required]
[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
[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; }
}
public partial class Staff
{
public Staff()
{
this.Tables = new HashSet<Tables>();
}
public int EmployeeID { get; set; }
public string First_name { get; set; }
public string Last_name { get; set; }
public string Telephone { get; set; }
public string Description { get; set; }
public string Username { get; set; }
public virtual ICollection<Tables> Tables { get; set; }
}
The controler is:
[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public ActionResult MultipleModelView(MultipleModel model)
{
if (ModelState.IsValid)
{
try
{
WebSecurity.CreateUserAndAccount(model.RegisterModel.UserName, model.RegisterModel.Password);
Roles.AddUserToRole(model.RegisterModel.UserName, "Customer");
Staff staff = new Staff();
staff.Username = model.RegisterModel.UserName;
staff.First_name = model.Staff.First_name;
staff.Last_name = model.Staff.Last_name;
staff.Telephone = model.Staff.Telephone;
db.Staff.Add(staff);
db.SaveChanges();
WebSecurity.Login(model.RegisterModel.UserName, model.RegisterModel.Password);
return RedirectToAction("Index", "Home");
}
catch (MembershipCreateUserException e)
{
ModelState.AddModelError("", ErrorCodeToString(e.StatusCode));
}
}
return View(model);
}
And View is:
#model test13.Models.MultipleModel
#{
ViewBag.Title = "MultipleModelView";
}
<h2>MultipleModelView</h2>
#using (Html.BeginForm("MultipleModelView", "Account", FormMethod.Post))
{
#Html.AntiForgeryToken()
#Html.ValidationSummary()
<fieldset>
<legend>Registration Form</legend>
<ol>
<li>
#Html.LabelFor(m => m.RegisterModel.UserName)
#Html.TextBoxFor(m => m.RegisterModel.UserName)
</li>
<li>
#Html.LabelFor(m => m.RegisterModel.Password)
#Html.PasswordFor(m => m.RegisterModel.Password)
</li>
<li>
#Html.LabelFor(m => m.RegisterModel.ConfirmPassword)
#Html.PasswordFor(m => m.RegisterModel.ConfirmPassword)
</li>
<li>
#Html.LabelFor(m => m.Staff.First_name)
#Html.TextBoxFor(m => m.Staff.First_name)
</li>
<li>
#Html.LabelFor(m => m.Staff.Last_name)
#Html.TextBoxFor(m => m.Staff.Last_name)
</li>
<li>
#Html.LabelFor(m => m.Staff.Telephone)
#Html.TextBoxFor(m => m.Staff.Telephone)
</li>
</ol>
<input type="submit" value="Register" />
</fieldset>
}
#section Scripts {
#Scripts.Render("~/bundles/jqueryval")
}
When i Fill data to the TextBoxs and Post them, App get me Exception in this part of code:
WebSecurity.CreateUserAndAccount(model.RegisterModel.UserName, model.RegisterModel.Password);
System.NullReferenceException: Object reference not set to an instance of an object.
Help me plese with this. Thank you.

Answer 1

Use properties and not fields in your view model:
public class MultipleModel
{
public Staff Staff { get; set; }
public RegisterModel RegisterModel { get; set; }
}
The default model binder in ASP.NET MVC works only with properties. Fields are ignored.

Answer 2

initializes register model in constructor
public class MultipleModel
{
public MultipleModel()
{
this.RegisterModel = new RegisterModel();
}
public Staff Staff{get;set;};
public RegisterModel RegisterModel{get;set;};
}