Validation of ViewModel throws exception - asp.net-mvc

I have a viewmodel that contains a product and SelectList of categories.
public class AdFormViewModel
{
public AmericanAds.Model.Ad Ad { get; set; }
public SelectList Categories { get; set; }
public AdFormViewModel(AmericanAds.Model.Ad ad, SelectList categories)
{
Ad = ad;
Categories = categories;
}
}
When adding a new product, if validation fails for category dropdown I get below error message.
The model item passed into the dictionary is of type 'AmericanAds.Model.Ad' but this dictionary requires a model item of type 'AmericanAds.Controllers.AdFormViewModel'.
Here is the controller for create action.
public ActionResult Create()
{
AdFormViewModel data = new AdFormViewModel(
null,
new SelectList(_repository.CategoryList().ToList(), "CategoryId", "CategoryName")
);
return View(data);
}
//
// POST: /Ad/Create
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(Ad ad)
{
if (ModelState.IsValid)
{
try
{
_repository.AddAd(ad);
return RedirectToAction("Index");
}
catch
{
return View(ad);
}
}
else
{
return View(ad);
}
}
What am I missing?
As you can tell, I am very new to ASP.Net MVC.
Thanks!

It's because your Create view requires a model of type AdFormViewModel but in your Create action (the one with the [AcceptVerbs(HttpVerbs.Post)] attribute) you return a model of type Ad (see the lines where it says return View(ad)).
Like the exception message says ; It requires an AmericanAds.Controllers.AdFormViewModel but you are sending an AmericanAds.Model.Ad.
And no, I don't think this has anything to do with the validation.

Related

Model Binding Object properties gets NULL on passing while Redirecting to another Action Method [duplicate]

I want to know, there is any technique so we can pass Model as a parameter in RedirectToAction
For Example:
public class Student{
public int Id{get;set;}
public string Name{get;set;}
}
Controller
public class StudentController : Controller
{
public ActionResult FillStudent()
{
return View();
}
[HttpPost]
public ActionResult FillStudent(Student student1)
{
return RedirectToAction("GetStudent","Student",new{student=student1});
}
public ActionResult GetStudent(Student student)
{
return View();
}
}
My Question - Can I pass student model in RedirectToAction?
Using TempData
Represents a set of data that persists only from one request to the
next
[HttpPost]
public ActionResult FillStudent(Student student1)
{
TempData["student"]= new Student();
return RedirectToAction("GetStudent","Student");
}
[HttpGet]
public ActionResult GetStudent(Student passedStd)
{
Student std=(Student)TempData["student"];
return View();
}
Alternative way
Pass the data using Query string
return RedirectToAction("GetStudent","Student", new {Name="John", Class="clsz"});
This will generate a GET Request like Student/GetStudent?Name=John & Class=clsz
Ensure the method you want to redirect to is decorated with [HttpGet] as
the above RedirectToAction will issue GET Request with http status
code 302 Found (common way of performing url redirect)
Just call the action no need for redirect to action or the new keyword for model.
[HttpPost]
public ActionResult FillStudent(Student student1)
{
return GetStudent(student1); //this will also work
}
public ActionResult GetStudent(Student student)
{
return View(student);
}
Yes you can pass the model that you have shown using
return RedirectToAction("GetStudent", "Student", student1 );
assuming student1 is an instance of Student
which will generate the following url (assuming your using the default routes and the value of student1 are ID=4 and Name="Amit")
.../Student/GetStudent/4?Name=Amit
Internally the RedirectToAction() method builds a RouteValueDictionary by using the .ToString() value of each property in the model. However, binding will only work if all the properties in the model are simple properties and it fails if any properties are complex objects or collections because the method does not use recursion. If for example, Student contained a property List<string> Subjects, then that property would result in a query string value of
....&Subjects=System.Collections.Generic.List'1[System.String]
and binding would fail and that property would be null
[HttpPost]
public async Task<ActionResult> Capture(string imageData)
{
if (imageData.Length > 0)
{
var imageBytes = Convert.FromBase64String(imageData);
using (var stream = new MemoryStream(imageBytes))
{
var result = (JsonResult)await IdentifyFace(stream);
var serializer = new JavaScriptSerializer();
var faceRecon = serializer.Deserialize<FaceIdentity>(serializer.Serialize(result.Data));
if (faceRecon.Success) return RedirectToAction("Index", "Auth", new { param = serializer.Serialize(result.Data) });
}
}
return Json(new { success = false, responseText = "Der opstod en fejl - Intet billede, manglede data." }, JsonRequestBehavior.AllowGet);
}
// GET: Auth
[HttpGet]
public ActionResult Index(string param)
{
var serializer = new JavaScriptSerializer();
var faceRecon = serializer.Deserialize<FaceIdentity>(param);
return View(faceRecon);
}
[NonAction]
private ActionResult CRUD(someModel entity)
{
try
{
//you business logic here
return View(entity);
}
catch (Exception exp)
{
ModelState.AddModelError("", exp.InnerException.Message);
Response.StatusCode = 350;
return someerrohandilingactionresult(entity, actionType);
}
//Retrun appropriate message or redirect to proper action
return RedirectToAction("Index");
}
i did find something like this, helps get rid of hardcoded tempdata tags
public class AccountController : Controller
{
[HttpGet]
public ActionResult Index(IndexPresentationModel model)
{
return View(model);
}
[HttpPost]
public ActionResult Save(SaveUpdateModel model)
{
// save the information
var presentationModel = new IndexPresentationModel();
presentationModel.Message = model.Message;
return this.RedirectToAction(c => c.Index(presentationModel));
}
}

Submitting form data to multiple tables. NullReferenceException

Hey could someone please help me submit this form? Here is my ViewModel that I made. This is my third day trying to pick up MVC so I'm still new to this.
public class EmployeeAllData
{
public Employees Employees { get; set; }
public PermissionModel PermissionModel { get; set; }
}
Here is my controller for the form submit. I'm starting with the permission table and I'm not having any luck. It keeps giving me this error: NullReferenceException was unhandled by user code. I tried hard coding values and it updated the permissions table just fine. I can't find out why I'm not getting a value back from Employees.
[HttpPost]
public ActionResult Create(EmployeeAllData viewModel)
{
var permission = new PermissionModel
{
EmployeesId = Convert.ToByte(viewModel.Employees.Id),
TimeStamp = DateTime.Now,
PermissionVal = viewModel.Employees.Permissions
};
_context.PermissionModels.Add(permission);
_context.SaveChanges();
return RedirectToAction("EmployeeList", "Employee");
}
Any ideas?
UPDATE
I think my problem is with my ViewModel. The code below runs fine and creates a new employee in the database.
public ActionResult Create(Employees employees)
{
_context.Employeeses.Add(employees);
_context.SaveChanges();
return RedirectToAction("EmployeeList", "Employee");
}
I did not need to use a viewModel. Here is my final code that now works.
[HttpPost]
public ActionResult Create(Employees employees)
{
_context.Employeeses.Add(employees);
_context.SaveChanges();
var permission = new PermissionModel()
{
EmployeesId = Convert.ToByte(employees.Id),
TimeStamp = DateTime.Now,
PermissionVal = employees.Permissions
};
_context.PermissionModels.Add(permission);
_context.SaveChanges();
return RedirectToAction("EmployeeList", "Employee");
}

Can we pass model as a parameter in RedirectToAction?

I want to know, there is any technique so we can pass Model as a parameter in RedirectToAction
For Example:
public class Student{
public int Id{get;set;}
public string Name{get;set;}
}
Controller
public class StudentController : Controller
{
public ActionResult FillStudent()
{
return View();
}
[HttpPost]
public ActionResult FillStudent(Student student1)
{
return RedirectToAction("GetStudent","Student",new{student=student1});
}
public ActionResult GetStudent(Student student)
{
return View();
}
}
My Question - Can I pass student model in RedirectToAction?
Using TempData
Represents a set of data that persists only from one request to the
next
[HttpPost]
public ActionResult FillStudent(Student student1)
{
TempData["student"]= new Student();
return RedirectToAction("GetStudent","Student");
}
[HttpGet]
public ActionResult GetStudent(Student passedStd)
{
Student std=(Student)TempData["student"];
return View();
}
Alternative way
Pass the data using Query string
return RedirectToAction("GetStudent","Student", new {Name="John", Class="clsz"});
This will generate a GET Request like Student/GetStudent?Name=John & Class=clsz
Ensure the method you want to redirect to is decorated with [HttpGet] as
the above RedirectToAction will issue GET Request with http status
code 302 Found (common way of performing url redirect)
Just call the action no need for redirect to action or the new keyword for model.
[HttpPost]
public ActionResult FillStudent(Student student1)
{
return GetStudent(student1); //this will also work
}
public ActionResult GetStudent(Student student)
{
return View(student);
}
Yes you can pass the model that you have shown using
return RedirectToAction("GetStudent", "Student", student1 );
assuming student1 is an instance of Student
which will generate the following url (assuming your using the default routes and the value of student1 are ID=4 and Name="Amit")
.../Student/GetStudent/4?Name=Amit
Internally the RedirectToAction() method builds a RouteValueDictionary by using the .ToString() value of each property in the model. However, binding will only work if all the properties in the model are simple properties and it fails if any properties are complex objects or collections because the method does not use recursion. If for example, Student contained a property List<string> Subjects, then that property would result in a query string value of
....&Subjects=System.Collections.Generic.List'1[System.String]
and binding would fail and that property would be null
[HttpPost]
public async Task<ActionResult> Capture(string imageData)
{
if (imageData.Length > 0)
{
var imageBytes = Convert.FromBase64String(imageData);
using (var stream = new MemoryStream(imageBytes))
{
var result = (JsonResult)await IdentifyFace(stream);
var serializer = new JavaScriptSerializer();
var faceRecon = serializer.Deserialize<FaceIdentity>(serializer.Serialize(result.Data));
if (faceRecon.Success) return RedirectToAction("Index", "Auth", new { param = serializer.Serialize(result.Data) });
}
}
return Json(new { success = false, responseText = "Der opstod en fejl - Intet billede, manglede data." }, JsonRequestBehavior.AllowGet);
}
// GET: Auth
[HttpGet]
public ActionResult Index(string param)
{
var serializer = new JavaScriptSerializer();
var faceRecon = serializer.Deserialize<FaceIdentity>(param);
return View(faceRecon);
}
[NonAction]
private ActionResult CRUD(someModel entity)
{
try
{
//you business logic here
return View(entity);
}
catch (Exception exp)
{
ModelState.AddModelError("", exp.InnerException.Message);
Response.StatusCode = 350;
return someerrohandilingactionresult(entity, actionType);
}
//Retrun appropriate message or redirect to proper action
return RedirectToAction("Index");
}
i did find something like this, helps get rid of hardcoded tempdata tags
public class AccountController : Controller
{
[HttpGet]
public ActionResult Index(IndexPresentationModel model)
{
return View(model);
}
[HttpPost]
public ActionResult Save(SaveUpdateModel model)
{
// save the information
var presentationModel = new IndexPresentationModel();
presentationModel.Message = model.Message;
return this.RedirectToAction(c => c.Index(presentationModel));
}
}

Model property is empty

I am trying to move from webForms to Asp.net-MVC and have some problems. I am trying to figure why this is not working, I am getting this error: "Object reference not set to an instance of an object"
I have the class 'Pages':
namespace _2send.Model
{
public class Pages
{
public string PageContent { get; set; }
public string PageName { get; set; }
public int LanguageId { get; set; }
}
}
I am inserting the value to 'Pages.PageContent' property with this class:
namespace _2send.Model.Services
{
public class PagesService : IPagesService
{
public void GetFooterlinksPage()
{
DB_utilities db_util = new DB_utilities();
SqlDataReader dr;
Pages pages = new Pages();
using (dr = db_util.procSelect("[Pages_GetPageData]"))
{
if (dr.HasRows)
{
dr.Read();
pages.PageContent = (string)dr["PageContent"];
dr.Close();
}
}
}
The Controller method looks like this:
private IPagesService _pagesService;
public FooterLinksPageController(IPagesService pagesService)
{
_pagesService = pagesService;
}
public ActionResult GetFooterLinksPage()
{
_pagesService.GetFooterlinksPage();
return View();
}
I am trying to write the property in the view like this:
#model _2send.Model.Pages
<div>
#Model.PageContent;
</div>
When debugging, the method is fired and the dataReader is inserting the value to the 'PageContent' property, but I am still getting this error from the view.
Thanks!
return View();
You didn't pass a model.
You need to pass the model as a parameter to the View() method.
You need to rewrite service method to return Pages:
public Pages GetFooterlinksPage()
{
DB_utilities db_util = new DB_utilities();
Pages pages = new Pages();
using (var dr = db_util.procSelect("[Pages_GetPageData]"))
{
if (dr.HasRows)
{
dr.Read();
pages.PageContent = (string)dr["PageContent"];
return pages;
// Because you use using, you don't need to close datareader
}
}
}
And then rewrite your action method:
public ActionResult GetFooterLinksPage()
{
var viewmodel = _pagesService.GetFooterlinksPage();
return View(viewmodel);
}
You can return a model:
var viewmodel = new _2send.Model.Pages().
//here you configure your properties
return View(viewmodel);

How can use MVC DropDownlist

I have a problem with DropDownlist in MVC
I use ModelView in my application and this is my code
namespace MedicallexiconProject.ViewModel
{
public class WordViewModel
{
private readonly ICategoryService _categoryService;
public WordViewModel(ICategoryService categoryService)
{
_categoryService = categoryService;
var selectList = _categoryService.GetAllCategorysSelectList().
Select(x => new SelectListItem
{
Text = x.Name,
Value = x.ID.ToString()
}).ToList();
Categories = selectList;
}
public WordViewModel()
{
}
public string Name { get; set; }
private IList<SelectListItem> _categories;
public IList<SelectListItem> Categories
{
get
{
if (_categories == null)
{
_categories = new List<SelectListItem>();
}
return (_categories);
}
set { _categories = value; }
}
}
}
and this is my controller
[HttpGet]
public ActionResult Create()
{
var wordViewModel = new WordViewModel(_categoryService);
ViewBag.CategoryID = wordViewModel.Categories;
return View();
}
[HttpPost]
public ActionResult Create(WordViewModel wordViewModel)
{
Mapper.CreateMap<WordViewModel, Word>();
var word = new Word();
Mapper.Map(wordViewModel, word);
if (ModelState.IsValid)
{
_wordService.AddNewWord(word);
_uow.SaveChanges();
return RedirectToAction("Index");
}
return View(wordViewModel);
}
Now how can I insert dropdownlist in my View?
As AlfalfaStrange mentioned, you should not add logic in your ViewModel. That makes it ugly ! Keep your ViewModel simple POCO.
Add one more property in your ViewModel called "SelectedCategoryID" like this
public class WordViewModel
{
public int SelectedCategoryID { set;get;}
public IList<SelectListItem> Categories { set;get;}
public string Name { set;get;}
}
Initialize your Items (Categories) of your ViewModel in your GET method. Here i am calling a method called GetCategories which returns a list of categories.I can simply call the method wherever i want.
public ActionResult Create()
{
var model=new WordViewModel();
model.Categories=YourService.GetCategories();
return View(model);
}
In your strongly typed Create view , use this
#model WordViewModel
using(#Html.BeginForm())
{
#Html.DropDownFor(x=>x.SelectedCategoryID,
new SelectList(Model.Categories,"Value","Text"),"Select Category")
<input type="submit" value="Save" />
}
In your HttpPost action method , you can check for wordViewModel.SelectedCategoryID for the selected value.
[HttpPost]
public ActionResult Create(WordViewModel wordViewModel)
{
if(ModelState.IsValid)
{
//Checck for wordViewModel.SelectedCategoryID here now
}
//some validation failed. Let's reload the category data again.
wordViewModel.Categories=YourService.GetCategories();
return View(wordViewModel);
}
It's absolutely fine to include code that loads a dropdown list in your view model. A select list and a drop down are both "view" items.... they are not related to business logic and your controller and model need not know anything about SelectLists or SelectListItems or DropDownList, etc.

Resources