I have a view which I load with product data. When I press the 'Add to Basket' button I'd like the same page to reload again but I'm getting errors such as:
Object reference not set to an instance of an object.
View:
#model List<Ecommerce.Models.HomeModels.Product>
#foreach (Ecommerce.Models.HomeModels.Product product in Model)
{ // above error points here!!!!!!!!!!!
using (Html.BeginForm())
{
<input type="hidden" name="productId" value="#product.ID" />
<input type="submit" value="Add to Basket"/>
}
}
Controller:
public ActionResult BuyProducts()
{
List<Models.HomeModels.Product> products = new List<Models.HomeModels.Product>();
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
//Method to load data into products
}
}
TempData["products"] = products;
return View(products);
}
[HttpPost]
[AllowAnonymous]
public ActionResult BuyProducts(string productID)
{
string id = productID;
return View(TempData["products"]);
}
TempData only exists for one request, so it is gone by the time you try to send it back (Which is why you get the error - TempData["products"] is null). Either way, you should use the post redirect get pattern, like this:
[HttpPost]
[AllowAnonymous]
public ActionResult BuyProducts(string productID)
{
string id = productID;
return RedirectToAction("BuyProducts");
}
The main reason is that if the user refreshes the page and you returned a view from post, the data will be posted a second time causing duplication.
TempData isn't persisted across requests. You can either use Session or ViewData to save "products"
Try one of those and see if that fixes your issue.
Related
I have an application where I have an html page which takes user input through a textbox.This is a REST Spring Framework and is divided as Controller, Entity, Service, Repository, View and the main application class.
I take an input value and search in the Mongodb database, If the value is present, I return the entity object from Service to Controller. The controller returns the same Entity View object.- PersonView in this case. I get a JSON Data.
The above scenario works well as long as there are records in the database. In case if the record is not present, it returns an empty JSON. My Controller returns Person View Object and I do not wish to change the signature and make the return type as String since in that case it returns the address on my HTML page.
Considering this, how should I handle the case when there are no records in the database and I wish to display a message on this same HTML page saying there are no records available.
I tried throwing an exception but in this case too, how Do I display message on my HTML considering that my Controller returns JSON object and I do not wish to change its signature?
Controller Class is as below:
public PersonView searchPerson(#PathVariable String pname) {
List<Person> pList= PersonService.searchPerson(pname);
PersonView personView = new PersonView();
personView.setPersonView(pList);
return personView;
EDIT:
Here is the function from personView Class that I call in Controller:
public List<Person> setPersonView() {
this.personView = personView;
}
Here is the service Impl class:
public List<Person> searchPerson(String name) throws Exception {
List<Person> personlist= new ArrayList<Person>();
personlist = personRepository.findByName(name);
if (personlist.isEmpty())
throw new Exception("Records not found in the the database");
return personlist;
}
Create a custom Exception class:
public class EntityNotFoundException extends RuntimeException {
public EntityNotFoundException(String message) {
super(message);
}
}
Now, in you controller code:
public List<Person> searchPerson(String name) {
List<Person> personlist= new ArrayList<Person>();
personlist = personRepository.findByName(name);
if (personlist.isEmpty()) {
throw new EntityNotFoundException("Records not found in the the database");
}
return personlist;
}
After that you can try something like this in you controller class:
private static final MappingJacksonJsonView JSON_VIEW = new MappingJacksonJsonView();
#ExceptionHandler(EntityNotFoundException.class)
public ModelAndView handleNotFoundException( Exception ex )
{
return new ModelAndView(JSON_VIEW, "error", new ErrorMessage("No Record in Db") );
}
Your ErrorMessage class can be a simple POJO:
public class ErrorMessage {
private String message;
ErrorMessage(String message) {
this.message = message;
}
public String getMessage() {
return message;
}
}
Although already answered, I will add some points here.
Please note that at some point of time you will have a requirement to send the
headers, Response body (with different Objects). So consider using ResponseEntity Object which will be a wrapper to your List. Here is the sample code.
public ResponseEntity<List<Person>> searchPerson(String name) {
List<Person> personlist= new ArrayList<Person>();
personlist = personRepository.findByName(name);
if (personlist.isEmpty()) {
return new ResponseEntity(new EntityNotFoundException("Records not found in the the database"), HttpStatus.BAD_REQUEST);
}
return new ResponseEntity(personlist , HttpStatus.OK);
}
Response Entity Object provides flexibility to greater extent. Read the documentation here.
https://docs.spring.io/spring/docs/current/javadocapi/org/springframework/http/ResponseEntity.html
I'm having an issue with a server side validation with Razor Pages (ASP.Net Core 2.0)
I have a page that creates a record
http://localhost:56876/Entries/Create?employeeID=112345
my code behind file for the OnGet looks like:
[BindProperty]
public EntryLog EntryLog { get; set; }
public Employee Employee{ get; set; }
public string empID { get; set; }
public IActionResult OnGet(string employeeID)
{
empID = employeeID;
// for Selects for lookup tables
ViewData["ReasonId"] = new SelectList(_context.Reason, "Id", "Name");
ViewData["ReasonTypeId"] = new SelectList(_context.ReasonType, "Id", "Name");
return Page();
}
The code above works just fine and client validation works perfect but I have business logic validation that if the Entry Date is 90 between today's date and hired date that I should not let the entry to be saved.
public async Task<IActionResult> OnPostAsync()
{
//Lookup current employeeID hiredDate. if is new employee do not continue.
Employee = await _context.Employee .FirstOrDefaultAsync(p => p.Id == EntryLog.EmployeeID);
//Server side validation
var age = DateTime.Today.Day - Employee.HireDate.Day;
if (age <= 90)
{
ModelState.AddModelError("NewEmp", "Emp is New Warning");
return Page();
}
if (!ModelState.IsValid)
{
return Page();
}
_context.EntryLog.Add(EntryLog);
await _context.SaveChangesAsync();
return RedirectToPage("./Index");
}
My server side validation works but the problem is that when I return Page();
The form gets refreshed and the two selects elements get empty out and the EmployeeID element gets empty out as well.
My guess is that the return Page() on OnPostAsync() is not calling the OnGet() method.
How can I keep the page as it is without loosing the info?
You are right the return Page() does not call OnGet() method. I´ll try to explain what is happening:
Short Answer:
When you receive the Post request (OnPost()) and return Page() the server just returns the response (html), it does not make a new Get Request so that OnGet() get called again.
The two selects elements are being cleant because they are set up in OnGet() through ViewData (that is temporary) not in OnPost(). My suggestion is that you set the "selects" again on OnPost() (extract to a method to make it easier).
Long Answer:
When you access your Page (Entries/Create) by typing or being redirected through a link, the browser request the page to the server using HTTP METHOD GET, which will invoke OnGet method. Afterwards, when you send your form (considering method="POST") the request will be sent to the server and be caught by the OnPost method.
When you code return Page(), it is not sending back a response to browser saying "Hey, you have to make a GET request again (what would make OnGet be called again)", it is returning the end response (html) itself. That´s why OnGet() is not being called. What would make the OnGet() be called again would be return RedirectToPage("./Entities/Create"), but doing so you would lose your Model state (validation result).
The two selects elements are being cleant because they are set up in OnGet() through ViewData (that is temporary) not in OnPost(). My suggestion is that you set the "selects" again on OnPost() (extract to a method to make it easier).
Regards.
You can simply call OnGet from your OnPost method, i.e.:
if (!ModelState.IsValid) {
return OnGet();
}
This works for me in ASP.NET Core 2.2 and preserves all validation errors.
I have already tried many solutions available on web as per my understanding in context to this question but being new in MVC I am still unable to find a solution. Kindly help.
I have a view which is the home page of the website named as "Index.cshtml" and is situated under the following path:
WebsiteName/Areas/Website/Views/CypressHome/Index.cshtml
Secondly, I have a created a user trial form as partial view named as "_PartialHomeFormFreeTrial.cshtml" which is situated under the following path:
WebsiteName/Areas/Website/Shared/_PartialHomeFormFreeTrial.cshtml.
This form I have used inside my "Index.cshtml" as below:
<!--freetrialform-->
#Html.Partial("_PartialHomeFormFreeTrial")
<!--//freetrialform-->
Now, my partial page is posting data comprising of following elements:
#using (Html.BeginForm("Create", "Customer", FormMethod.Post))
{
#Html.AntiForgeryToken()
<div>
#Html.EditorFor(model => model.CustomerName, new { htmlAttributes = new { #class = "input__field input__field--kuro" } })
#Html.ValidationMessageFor(model => model.CustomerName, "", new { #class = "text-danger" })
............
other fields such as email, phone, date, etc..
<input type="submit" id="" value="SEND REQUEST" />
</div>
}
Now, I have created a controller named "CustomerController" which has the following code to save the data of the form as used as partial view in the main view "Index.cshtml":
public class CustomerController : Controller
{
private WebsiteContext db = new WebsiteContext();
// GET: Website/Customer
public ActionResult Index()
{
return View();
}
// GET: Website/Customer/Create
public ActionResult Create()
{
ViewBag.StatusPlanID = new SelectList(db.StatusPlans, "StatusPlanID", "Status");
return View("Index");
}
// POST: Website/Customer/Create
[HttpPost]
public ActionResult Create([Bind(Include = "CustomerID,CustomerName,CustomerEmail,CustomerPhone,DateOfRegistration,StatusPlanID")] Customer customer)
{
if (ModelState.IsValid)
{
db.Customers.Add(customer);
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.StatusPlanID = new SelectList(db.StatusPlans, "StatusPlanID", "Status", customer.StatusPlanID);
return View(customer);
}
}
I have tried many changes in my controller, return in the views and
many other things but I am getting the same error always. Neither the
validations are working nor the validated data is getting saved.
The error is as below:
Server Error in '/' Application.
The view 'Create' or its master was not found or no view engine supports the searched locations. The following locations were searched:
~/Areas/Website/Views/Customer/Create.aspx
~/Areas/Website/Views/Customer/Create.ascx
~/Areas/Website/Views/Shared/Create.aspx
~/Areas/Website/Views/Shared/Create.ascx
~/Views/Customer/Create.aspx
~/Views/Customer/Create.ascx
~/Views/Shared/Create.aspx
~/Views/Shared/Create.ascx
~/Areas/Website/Views/Customer/Create.cshtml
~/Areas/Website/Views/Customer/Create.vbhtml
~/Areas/Website/Views/Shared/Create.cshtml
~/Areas/Website/Views/Shared/Create.vbhtml
~/Views/Customer/Create.cshtml
~/Views/Customer/Create.vbhtml
~/Views/Shared/Create.cshtml
~/Views/Shared/Create.vbhtml
And the url is changing as below:
1. On running the system initially: http://localhost:53872/
2. On clicking on submit: http://localhost:53872/Areas/Website/Customer/Create along with the
error as stated above.
For more information my WebsiteAreaRegistration.cs file contains the below code:
public class WebsiteAreaRegistration : AreaRegistration
{
public override string AreaName
{
get
{
return "Website";
}
}
public override void RegisterArea(AreaRegistrationContext context)
{
context.MapRoute(
"Website_home",
"",
new { controller = "CypressHome", action = "Index", id = UrlParameter.Optional }
);
context.MapRoute(
"Website_default",
"Areas/Website/{controller}/{action}/{id}",
new { controller = "CypressHome", action = "Index", id = UrlParameter.Optional }
);
}
}
Though I have understood the problem but unable to figure out. Kindly help.
In your code last return statement is return View(customer). That's means after POST data it return a View (using HTTP GET method) as same name as Action that's Create. But your description you have a Create Action but you have no view page.
So please create a Create.cshtml with a Model corresponding customer Object.
Or change the return statement.
Based on your comment you can follow this Change.
1.Remove
public ActionResult Create()
{
ViewBag.StatusPlanID = new SelectList(db.StatusPlans, "StatusPlanID", "Status");
return View("Index");
}
2.then change
public ActionResult Index()
{
ViewBag.StatusPlanID = new SelectList(db.StatusPlans, "StatusPlanID", "Status");
return View(new Customer());
}
3.in Index.cshtml
#Model Customer
#Html.Partial("_PartialHomeFormFreeTrial",Model)
4.Then
return View("Index",customer);
I have the following view model
public class ProjectVM
{
....
[Display(Name = "Category")]
[Required(ErrorMessage = "Please select a category")]
public int CategoryID { get; set; }
public IEnumerable<SelectListItem> CategoryList { get; set; }
....
}
and the following controller method to create a new Project and assign a Category
public ActionResult Create()
{
ProjectVM model = new ProjectVM
{
CategoryList = new SelectList(db.Categories, "ID", "Name")
}
return View(model);
}
public ActionResult Create(ProjectVM model)
{
if (!ModelState.IsValid)
{
return View(model);
}
// Save and redirect
}
and in the view
#model ProjectVM
....
#using (Html.BeginForm())
{
....
#Html.LabelFor(m => m.CategoryID)
#Html.DropDownListFor(m => m.CategoryID, Model.CategoryList, "-Please select-")
#Html.ValidationMessageFor(m => m.CategoryID)
....
<input type="submit" value="Create" />
}
The view displays correctly but when submitting the form, I get the following error message
InvalidOperationException: The ViewData item that has the key 'CategoryID' is of type 'System.Int32' but must be of type 'IEnumerable<SelectListItem>'.
The same error occurs using the #Html.DropDownList() method, and if I pass the SelectList using a ViewBag or ViewData.
The error means that the value of CategoryList is null (and as a result the DropDownListFor() method expects that the first parameter is of type IEnumerable<SelectListItem>).
You are not generating an input for each property of each SelectListItem in CategoryList (and nor should you) so no values for the SelectList are posted to the controller method, and therefore the value of model.CategoryList in the POST method is null. If you return the view, you must first reassign the value of CategoryList, just as you did in the GET method.
public ActionResult Create(ProjectVM model)
{
if (!ModelState.IsValid)
{
model.CategoryList = new SelectList(db.Categories, "ID", "Name"); // add this
return View(model);
}
// Save and redirect
}
To explain the inner workings (the source code can be seen here)
Each overload of DropDownList() and DropDownListFor() eventually calls the following method
private static MvcHtmlString SelectInternal(this HtmlHelper htmlHelper, ModelMetadata metadata,
string optionLabel, string name, IEnumerable<SelectListItem> selectList, bool allowMultiple,
IDictionary<string, object> htmlAttributes)
which checks if the selectList (the second parameter of #Html.DropDownListFor()) is null
// If we got a null selectList, try to use ViewData to get the list of items.
if (selectList == null)
{
selectList = htmlHelper.GetSelectData(name);
usedViewData = true;
}
which in turn calls
private static IEnumerable<SelectListItem> GetSelectData(this HtmlHelper htmlHelper, string name)
which evaluates the the first parameter of #Html.DropDownListFor() (in this case CategoryID)
....
o = htmlHelper.ViewData.Eval(name);
....
IEnumerable<SelectListItem> selectList = o as IEnumerable<SelectListItem>;
if (selectList == null)
{
throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture,
MvcResources.HtmlHelper_WrongSelectDataType,
name, o.GetType().FullName, "IEnumerable<SelectListItem>"));
}
Because property CategoryID is typeof int, it cannot be cast to IEnumerable<SelectListItem> and the exception is thrown (which is defined in the MvcResources.resx file as)
<data name="HtmlHelper_WrongSelectDataType" xml:space="preserve">
<value>The ViewData item that has the key '{0}' is of type '{1}' but must be of type '{2}'.</value>
</data>
according to stephens (user3559349) answer, this can be useful:
#Html.DropDownListFor(m => m.CategoryID, Model.CategoryList ?? new List<SelectListItem>(), "-Please select-")
or in ProjectVM:
public class ProjectVM
{
public ProjectVM()
{
CategoryList = new List<SelectListItem>();
}
...
}
Most Likely Caused some sort of error redirecting to your page and you not initializing your model's drop down lists again.
Make sure that you initialize your drop downs in either the model's constructor or every time before you send said model to the page.
Otherwise you will need to maintain the state of the drop down lists either through the view bag or through the hidden value helpers.
OK, the poster's canned answer neatly explained why the error occurred, but not how to get it to work. I'm not sure that's really an answer, but it did point me in the right direction.
I ran into the same issue and found a slick way to resolve it. I'll try to capture that here. Disclaimer - I work on web pages once a year or so and really don't know what I'm doing most of the time. This answer should in no way be considered an "expert" answer, but it does the job with little work...
Given that I have some data object (most likely a Data Transfer Object) that I want to use a drop-down list to supply valid values for a field, like so:
public class MyDataObject
{
public int id;
public string StrValue;
}
Then the ViewModel looks like this:
public class MyDataObjectVM
{
public int id;
public string StrValue;
public List<SectListItem> strValues;
}
The real problem here, as #Stephen so eloquently described above, is the select list isn't populated on the POST method in the controller. So your controller methods would look like this:
// GET
public ActionResult Create()
{
var dataObjectVM = GetNewMyDataObjectVM();
return View(dataObjectVM); // I use T4MVC, don't you?
}
private MyDataObjectVM GetNewMyDataObjectVM(MyDataObjectVM model = null)
{
return new MyDataObjectVM
{
int id = model?.Id ?? 0,
string StrValue = model?.StrValue ?? "",
var strValues = new List<SelectListItem>
{
new SelectListItem {Text = "Select", Value = ""},
new SelectListITem {Text = "Item1", Value = "Item1"},
new SelectListItem {Text = "Item2", Value = "Item2"}
};
};
}
// POST
public ActionResult Create(FormCollection formValues)
{
var dataObject = new MyDataObject();
try
{
UpdateModel(dataObject, formValues);
AddObjectToObjectStore(dataObject);
return RedirectToAction(Actions.Index);
}
catch (Exception ex)
{
// fill in the drop-down list for the view model
var dataObjectVM = GetNewMyDataObjectVM();
ModelState.AddModelError("", ex.Message);
return View(dataObjectVM);
)
}
There you have it. This is NOT working code, I copy/pasted and edited to make it simple, but you get the idea. If the data members in both the original data model and the derived view model have the same name, UpdateModel() does an awesome job of filling in just the right data for you from the FormCollection values.
I'm posting this here so I can find the answer when I inevitably run into this issue again -- hopefully it will help someone else out as well.
I had the same problem, I was getting an invalid ModelState when I tried to post the form. For me, this was caused by setting CategoryId to int, when I changed it to string the ModelState was valid and the Create method worked as expected.
In my case the first ID in my list was zero, once I changed the ID to start from 1, it worked.
I'm attempting to make a simple page that will compare multiple form submissions.
I have a html page with a form, and a for-loop that generates a div for each item in a list of form submissions. The list is passed from the controller. I am trying to maintain the list in the controller rather than rely on a database.
When I try to resubmit the form, which should add another object to the list, the list re initializes.
In debugging, I see that the list is empty when the form gets submitted. I'm unsure as to the correct terminology, but it seems that the list is emptied whenever the view is rendered. Is there a way to maintain list contents?
I know there are better ways to do this, and welcome any advice. I'm still learning, so pleas go easy.
Thanks!
This is the simplified controller.
namespace MvcApplication2.Controllers
{
public class HomeController : Controller
{
List<paymentPlan> plansList = new List<paymentPlan>();
public ActionResult Index()
{
return View(plansList);
}
[HttpPost]
public ActionResult Index(FormCollection collection)
{
paymentPlan Project = new paymentPlan();
Project.customerName = Convert.ToString(collection["customerName"]);
plansList.Add(Project);
return View(plansList);
}
}
}
This is my simplified view.
#model List<MvcApplication2.Models.paymentPlan>
#using (Html.BeginForm("index", "home", FormMethod.Post, new { Id = "signupForm" }))
{
<label for="customerName">Customer Name:</label>
<input type="text" name="customerName" class="form-control required" />
#Html.ValidationSummary(true)
<input type="submit" value="Calculate" class="btn btn-primary" />
}
#{
bool isEmpty = !Model.Any();
if (!isEmpty)
{
foreach (var i in Model)
{
<div>
Name: #i.customerName
</div>
}
}
}
This is my simplified model.
namespace MvcApplication2.Models
{
public class paymentPlan
{
public string customerName { get; set; }
}
}
I think that's a question of controller and asp.Net MVC lifecycle !
A controller lifetime is the same as the request, for each request a new controller is created and once the work is done it's disposed!
So try to remove this List<paymentPlan> plansList = new List<paymentPlan>(); and work with TempData[] or ViewData[] or Session[] like this :
Controller
public class HomeController : Controller
{
public ActionResult Index()
{
Session["plansList"] = ((List<paymentPlan>)Session["plansList"])!=null? (List<paymentPlan>)Session["plansList"] : new List<paymentPlan>();
return View((List<paymentPlan>)Session["plansList"]);
}
[HttpPost]
public ActionResult Index(FormCollection collection)
{
paymentPlan Project = new paymentPlan();
Project.customerName = Convert.ToString(collection["customerName"]);
((List<paymentPlan>)Session["plansList"]).Add(Project);
return View(plansList);
}
}
check this : http://www.asp.net/mvc/overview/getting-started/lifecycle-of-an-aspnet-mvc-5-application