Unusual behavior DropDownList MVC 5 - asp.net

Question

I managed to populate DropDownList with value from a Database in ASP.NET MVC 5. My goal is to assing one of the dropDownList's value to a specific model, and send it back to the Database. So, if i leave the default value in the dropdownlist, the data in SQL server is null, which is Okay, but if I choose an option, I get an error :
Exception thrown: 'System.InvalidOperationException' in System.Web.Mvc.dll ("There is no ViewData item of type 'IEnumerable' that has the key 'Status'."). I tried everything so far and i am opened for suggestions. Thank you !!!
In Controller :
ViewBag.Status = new SelectList(db.Status, "Id", "Name");
in View
#Html.DropDownList("Status","Select status...")
In Controller so far..
public ActionResult Index()
{
return View();
}
[HttpGet]
public ActionResult Apply(ViewModelVM vm,int x=0)
{
myDb db = new myDb();
ViewBag.SocialStatus = new SelectList(db.SocialStatuses, "Id", "StatusDescription");
return View();
}
[HttpPost]
public ActionResult Apply(ViewModelVM vm)
{
if (ModelState.IsValid)
{
using (myDb db = new myDb())
{
var personalinfo = new PersonalInformation()
{
FirstName = vm.PersonalInformation.FirstName,
LastName = vm.PersonalInformation.LastName,
Birthdate = vm.PersonalInformation.Birthdate,
SocialStatus = vm.SocialStatus
};
ViewBag.SocialStatus = new SelectList(db.SocialStatuses, "Id", "StatusDescription");
db.PersonalInformations.Add(personalinfo);
db.SaveChanges();
}
return View("Success");
}
return View();
}
The model:
public partial class Status
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public SocialStatus()
{
PersonalInformations = new HashSet<PersonalInformation>();
}
public int Id { get; set; }
[StringLength(20)]
public string StatusDescription { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<PersonalInformation> PersonalInformations { get; set; }
}
}
The ViewModel:
public class ViewModelVM
{
...
public Status SocialStatus { set; get; }
...
}

Answer 1

Firstly your using a view model so include a property in your view model for the SelectList
public IEnumerable<SelectListItem> StatusList { get; set; }
Next remove the parameter for the model from the GET method (and since you don't appear to be using the value of x, that should be removed also)
[HttpGet]
public ActionResult Apply(ViewModelVM vm,int x=0)
{
myDb db = new myDb();
ViewModelVM model = new ViewModelVM()
{
StatusList = new SelectList(db.SocialStatuses, "Id", "StatusDescription");
};
return View(model); // return the model to the view
}
Next, your dropdown is binding to a property named Status but your view model does not contain a property named status (its SocialStatus) and SocialStatus is a complex object and you cannot bind a <select> to a complex object (a <select> only posts back a single value (or array or values in the case of <select multiple>).
In addition, because your view model contains a property which is a complex object with validation attributes on its properties, ModelState will always be invalid because you do not post back a value for StatusDescription. As a result you always return the view in the POST method, and because you have not reassigned ViewBag.Status = ...., it is null, hence the error.
Remove property public Status SocialStatus { set; get; } and include
[Display(Name = "Social Status")]
[Required(ErrorMessage = "Please select a status")]
public int SocialStatus { get; set; }
an then in the view, strongly bind to your model using
#Html.LabelFor(m => m.SocialStatus)
#Html.DropDownListFor(m => m.SocialStatus, Model.StatusList, "-Please select-")
#Html.ValidationMessageFor(m => m.SocialStatus)
Then, in the POST method, if ModelState is invalid, populate the select list again before returning the view
if(!ModelState.IsValid)
{
model.StatusList = new SelectList(db.SocialStatuses, "Id", "StatusDescription");
return View(model);
}
// save and redirect
Finally, review What is ViewModel in MVC?.