I am redirecting the view from [HttpPost] method to [HttpGet] method. I have gotten it to work, but want to know if this is the best way to do this.
Here is my code:
[HttpPost]
public ActionResult SubmitStudent()
{
StudentViewModel model = TempData["model"] as StudentResponseViewModel;
TempData["id"] = model.Id;
TempData["name"] = model.Name;
return RedirectToAction("DisplayStudent");
}
[HttpGet]
public ActionResult DisplayStudent()
{
ViewData["id"] = TempData["id"];
ViewData["name"] = TempData["name"];
return View();
}
View:
<%# Page
Language="C#"
Inherits="System.Web.Mvc.ViewPage"
%>
<html>
<head runat="server">
<title>DisplayStudent</title>
</head>
<body>
<div>
<%= ViewData["id"]%> <br />
<%= ViewData["name"]%>
</div>
</body>
</html>
There are basically 3 techniques in ASP.NET MVC to implement the PRG pattern.
TempData
Using TempData is indeed one way of passing information for a single redirect. The drawback I see with this approach is that if the user hits F5 on the final redirected page he will no longer be able to fetch the data as it will be removed from TempData for subsequent requests:
[HttpPost]
public ActionResult SubmitStudent(StudentResponseViewModel model)
{
if (!ModelState.IsValid)
{
// The user did some mistakes when filling the form => redisplay it
return View(model);
}
// TODO: the model is valid => do some processing on it
TempData["model"] = model;
return RedirectToAction("DisplayStudent");
}
[HttpGet]
public ActionResult DisplayStudent()
{
var model = TempData["model"] as StudentResponseViewModel;
return View(model);
}
Query string parameters
Another approach if you don't have many data to send is to send them as query string parameters, like this:
[HttpPost]
public ActionResult SubmitStudent(StudentResponseViewModel model)
{
if (!ModelState.IsValid)
{
// The user did some mistakes when filling the form => redisplay it
return View(model);
}
// TODO: the model is valid => do some processing on it
// redirect by passing the properties of the model as query string parameters
return RedirectToAction("DisplayStudent", new
{
Id = model.Id,
Name = model.Name
});
}
[HttpGet]
public ActionResult DisplayStudent(StudentResponseViewModel model)
{
return View(model);
}
Persistence
Yet another approach and IMHO the best consists into persisting this model into some data store (like a database or something and then when you want to redirect to the GET action send only an id allowing for it to fetch the model from wherever you persisted it). Here's the pattern:
[HttpPost]
public ActionResult SubmitStudent(StudentResponseViewModel model)
{
if (!ModelState.IsValid)
{
// The user did some mistakes when filling the form => redisplay it
return View(model);
}
// TODO: the model is valid => do some processing on it
// persist the model
int id = PersistTheModel(model);
// redirect by passing the properties of the model as query string parameters
return RedirectToAction("DisplayStudent", new { Id = id });
}
[HttpGet]
public ActionResult DisplayStudent(int id)
{
StudentResponseViewModel model = FetchTheModelFromSomewhere(id);
return View(model);
}
Each method has its pros and cons. Up to you to choose which one suits best to your scenario.
If you are inserting this data into a database then you should redirect them to a controller action that has this data in the route:
/Students/View/1
You can then write code in the controller to retrieve the data back from the database for display:
public ActionResult View(int id) {
// retrieve from the database
// create your view model
return View(model);
}
One of the overrides of RedirectToAction() looks like that:
RedirectToAction(string actionName, object routeValues)
You can use this one as:
[HttpPost]
public ActionResult SubmitStudent()
{
StudentViewModel model = TempData["model"] as StudentResponseViewModel;
return RedirectToAction("DisplayStudent", new {id = model.ID, name = model.Name});
}
[HttpGet]
public ActionResult DisplayStudent(string id, string name)
{
ViewData["id"] = TempData["id"];
ViewData["name"] = TempData["name"];
return View();
}
Hope that works.
This is the classic Post-Redirect-Get pattern (PRG) and it looks fine but I would add one bit of code. In the DisplayStudent method check if your TempData variables are not null otherwise do a redirect to some default Index action. This is in case a user presses F5 to refresh the page.
public ActionResult DisplayStudent()
{
if(TempData["model"] == null)
{
return RedirectToAction("Index");
}
var model = (StudentResponseViewModel)TempData["model"];
return View(model);
}
public ViewResult Index()
{
IEnumerable<StudentResponseViewModel> students = GetAllStudents();
return View(students);
}
Related
I'm new to MVC and trying to create a wizard-style series of views, passing the same model instance from one view to the next, where the user completes a little more information on each form. The controller looks something like this:-
[HttpGet]
public ActionResult Step1()
{
return View();
}
[HttpPost]
public ActionResult Step1(MyModel model)
{
if (!ModelState.IsValid)
return View(model);
return View("Step2", model);
}
[HttpPost]
public ActionResult Step2(MyModel model)
{
if (!ModelState.IsValid)
return View(model);
return View("Step3", model);
}
// etc..
Questions:-
When I submit the form from the Step1 view, it calls the Step1 POST method and results in the Step2 view being displayed in the browser. When I submit the form on this view, it calls the Step1 POST method again! I got it to work by specifying the action and controller name in Html.BeginForm(), so I'm guessing that the parameterless overload just POSTs back to the action that rendered the view?
I've noticed that the browser's address bar is out of sync with the current view - when I'm on the Step2 view it still shows the Step1 URL, and when on Step3 it shows the Step2 URL. What's going on?
Another approach I've seen for passing a model between views is to put the model in TempData then use RedirectToAction(). What are the pros and cons of this method versus what I'm currently doing?
I won't be providing any "back" buttons of my own in the wizard. Are there any pitfalls to be aware of regarding the browser's back button, and do either of the above two approaches help (or hinder)?
Edit
Prompted by #StephenMuecke's comment I've now rewritten this to use a single view. I tried this once before but had difficulties round-tripping a "step number" to keep track of where I was in the wizard. I was originally using a hidden field created with #Html.HiddenFor', but this wasn't updating as the underlying model property changed. This appears to be "by design", and the workaround is to create the hidden field using vanilla HTML (
Anyway the one-view wizard is now working. The only problem is the old chestnut of the user being able to click the back button after they have completed the wizard, make a change, and resubmit a second time (resulting in a second DB record).
I've tried adding [OutputCache(NoStore = true, Duration = 0, VaryByParam = "None")] to my POST method, but all this does is display (in my case) a Chrome error page suggesting that the user clicks refresh to resubmit the form. This isn't user friendly and doesn't prevent a second submit.
you can use RedirectToAction() in this case without worrying about TempData. Just add your model as a parameter to each action and use RedirectToAction("Step2", model);
[HttpGet]
public ActionResult Step1()
{
return View();
}
[HttpPost]
public ActionResult Step1(MyModel model)
{
if (!ModelState.IsValid)
return View(model);
return RedirectToAction("Step2", model);
}
[HttpGet]
public ActionResult Step2(MyModel model)
{
return View(model);
}
[HttpPost]
public ActionResult Step2(MyModel model)
{
if (!ModelState.IsValid)
return View(model);
return RedirectToAction("Step3", model);
}
// etc..
The answer to #1 is found in #2.. if you dont specify the Action in you Html.BeginForm() it posts to the current url.
Using TempData to avoid model displaying in url.
[HttpGet]
public ActionResult Step1()
{
return View();
}
[HttpPost]
public ActionResult Step1(MyModel model)
{
if (!ModelState.IsValid)
return View(model);
TempData["myModel"] = model;
return RedirectToAction("Step2");
}
[HttpGet]
public ActionResult Step2()
{
var model = TempData["myModel"] as MyModel;
return View(model);
}
[HttpPost]
public ActionResult Step2(MyModel model)
{
if (!ModelState.IsValid)
return View(model);
TempData["myModel"] = model;
return RedirectToAction("Step3");
}
// etc..
Another option would be to add the name of the next action to ViewBag and set your actionName in each BeginForm()
[HttpGet]
public ActionResult Step1()
{
ViewBag.NextStep = "Step1";
return View();
}
[HttpPost]
public ActionResult Step1(MyModel model)
{
if (!ModelState.IsValid)
{
ViewBag.NextStep = "Step1";
return View(model);
}
ViewBag.NextStep = "Step2";
return View("Step2", model);
}
[HttpPost]
public ActionResult Step2(MyModel model)
{
if (!ModelState.IsValid)
{
ViewBag.NextStep = "Step2";
return View(model);
}
ViewBag.NextStep = "Step3";
return View("Step3", model);
}
//View
#using (Html.BeginForm((string)ViewBag.NextStep, "ControllerName"))
{
}
I'd prefer to add NextStep as a property to MyModel and using that instead of using ViewBag though.
I understand the thought behind your approach and don't have any issues with it. Unfortunately, I don't believe that ASP.NET MVC is geared very well for passing the the same view model (with data!) between different actions.
Typically, the scaffolded actions in the controller will either create a model item or find it by identifier in the database.
I don't know if this would help, but you could try to save it to the database on every step, and then retrieve it by identifier, or you could also save it to a session and grab it that way.
One issue I do see with your approach is you have Step2 set as a get, yet you probably want to post data to it from Step1 instead of using a query string. You may need to reconcile that issue.
So I have a simple action in my controller. The project is a MVC Mobile Application.
public ActionResult Index()
{
return View();
}
this gives an form to enter data. I then handle the data in the post back.
[HttpPost]
public ActionResult Index(ScanViewModel model)
{
if (ModelState.IsValid)
{
Scan ns = new Scan();
ns.Location = model.Location;
ns.Quantity = model.Quantity;
ns.ScanCode = model.ScanCode;
ns.Scanner = User.Identity.Name;
ns.ScanTime = DateTime.Now;
_db.Scans.Add(ns);
_db.SaveChanges();
}
return View(model);
}
I want to clear the fields in the form and allow users to enter data again. However I get the exact same values back into my inputs. How can I clear them in the controller.
Just call this.ModelState.Clear()
You should follow the PRG pattern.
Just redirect to the Action method which is meant for the Create Screen. You can use the RedirectToAction method to do so.
RedirectToAction returns an HTTP 302 response to the browser, which causes the browser to make a GET request to the specified action.
[HttpPost]
public ActionResult Index(ScanViewModel model)
{
if(ModelState.IsValid)
{
//Code for save here
//..............
_db.SaveChanges();
return RedirectToAction("Index","User");
}
return View(model);
}
public ActionResult Index()
{
return View();
}
Assuming your controller name is UserController.
I'd like show a form with some field (one in the example), submit it, save and display the same page with a reset of all fields. The probelm when I submit, I go the "Save" action but when I display the view the form is still filled in.
The model :
public class TestingModel
{
public string FirstName { get; set; }
}
The controller :
public class ChildController : Controller
{
public ActionResult Index()
{
TestingModel model = new TestingModel();
return View(model);
}
public ActionResult Save(TestingModel model)
{
Console.WriteLine(model.FirstName); //OK
//Save data to DB here ...
TestingModel testingModel = new TestingModel() { FirstName = string.Empty };
return View("Index", testingModel);
}
}
The view :
#using (Html.BeginForm("Save", "Child",FormMethod.Post))
{
#Html.TextBoxFor( m => m.FirstName)
<input type="submit" id="btSave" />
}
When Id debug to the view, in "Immediat window" Model.FirstName = "" but when the page is show I still have the value posted. I tried a ReditrectionToAction("Index") at the end of the Save method but same result.
Do you have an idea ?
Thanks,
If you want to do this you need to clear everything that's in the ModelState. Otherwise HTML helpers will completely ignore your model and use data from ModelState when binding their values.
Like this:
[HttpPost]
public ActionResult Save(TestingModel model)
{
//Save data to DB here ...
ModelState.Clear();
TestingModel testingModel = new TestingModel() { FirstName = string.Empty };
return View("Index", testingModel);
}
or simply redirect to the Index GET action in case of success:
[HttpPost]
public ActionResult Save(TestingModel model)
{
//Save data to DB here ...
return RedirectToAction("Index");
}
Try to return Index view without any model
return View("Index");
You should be posting your form back to the same ActionResult
public ActionResult Index()
{
TestingModel model = new TestingModel();
return View(model);
}
[HttpPost]
public ActionResult Index(TestingModel model)
{
Console.WriteLine(model.FirstName); //OK
//Save data to DB here ...
return RedirectToAction("Index");
}
You would be able to use the parameterless overload for BeginForm too
#using(Html.BeginForm())
{
//form
}
Non-HttpPost
public ActionResult Edit(int id)
{
var model = repository.GetModel(id);
if(model==null) return View("NotFound");
return View(model);
}
HttpPost
[HttpPost]
public ActionResult Edit()
{
// First of all, we retrieve the id from the posted form field.
// But I don't know how to do.
var model = repository.GetModel(id);
if(model==null) return View("NotFound");
if(!TryUpdateModel(model))
return View(model);
repository.SaveChanges();
RedirectToAction("Status","Controller");
}
Is it possible to retrieve the posted form fields from within a parameterless HttpPost action method?
For posted form values:
var id = Request.Form["id"];
or:
[HttpPost]
public ActionResult Edit(FormCollection fc)
{
var id = fc["id"];
...
}
or for any request value (including form posted):
var id = Request["id"];
I've this controller's method for create
[HttpPost]
public ActionResult Create(Topic topic)
{
if (ModelState.IsValid)
{
topicRepo.Add(topic);
topicRepo.Save();
return RedirectToAction("Details", new { id = topic.ID });
}
return View(topic);
}
and this for edit
[HttpPost]
public ActionResult Edit(int id, FormCollection formCollection)
{
Topic topic = topicRepo.getTopic(id);
if (ModelState.IsValid)
{
UpdateModel<Topic>(topic);
topicRepo.Save();
return RedirectToAction("Details", new { id = topic.ID });
}
return View(topic);
}
Both of these methods use common partial page (.ascx).
Validation works when I try to create topic but doesn't work when I try to edit it
That's normal. In the first example you are using a model as action parameter. When the default model binder tries to bind this model from the request it will automatically invoke validation and when you enter the action the ModelState.IsValid is already assigned.
In the second example your action takes no model, only a key/value collection and without a model validation makes no sense. Validation is triggered by the UpdateModel<TModel> method which in your example is invoked after the ModelState.IsValid call.
So you could try this:
[HttpPost]
public ActionResult Edit(int id)
{
Topic topic = topicRepo.getTopic(id);
UpdateModel<Topic>(topic);
if (ModelState.IsValid)
{
topicRepo.Save();
return RedirectToAction("Details", new { id = topic.ID });
}
return View(topic);
}