Lets say we have a class with a property called PetsName. If it is left blank on the screen I want to update the value provider so if the user doesn't enter a pet name, we force 'unnamed'. This isn't the actual scenario.. this is of course a sample, so answers like 'just set default values on a webpage, etc' won't fit this scenario : )
The main issue is we want to update the values so when you update the model it will use whatever you have overridden. I guess one idea is to remove the value and add it. When I check ModelState, it does have the updated value, however when I call TryUpdateModel, the value is not updated. Its possible what Im doing below is indeed correct and there is another issue here but I figured I'd try this first. Thanks!
//Sample case:
[HttpPost]
public ActionResult Edit(PetOwner petOwner)
{
//If pets name is not set, force to "Unknown"
if(petOwner.PetsName=="")
{
//Tried this too ModelState.Remove("PetsName");
//ModelState.Add("PetsName", new ModelState());
ModelState["PetsName"].Value = new ValueProviderResult("Unnamed", "Unnamed", CultureInfo.CurrentCulture);
}
//Get the record/relationships from DB to merge with ModelState
PetOwner petOwnerToSave = from o in ctx.PetOwners where o.PetOwnerId == petOwner.PetOwnerId select o;
TryUpdateModel(petOwnerToSave);
//Save petOwnerToSave
}
The real issue behind the scenes here is that Html.HiddenFor wasn't displaying the correct value even though TryUpdateModel was updating a value in the model to give to the view.
The issue here is that the Html helpers assume if you are rendering a view after a post, there mustve been an error (otherwise you wouldve redirected back to the view with a GET method - hence the Post Redirect Get issue)
This is described in detail at:
http://blogs.msdn.com/b/simonince/archive/2010/05/05/asp-net-mvc-s-html-helpers-render-the-wrong-value.aspx
Related
I have an MVC 5 website - with a controller. If the ModelState.IsValid - then I perform some actions.
If it's invalid I need to tell the user the error (in ViewBag.Message) - and pass the invalid model back to the view so the user can see and edit it.
so this works at the end of the controller action:
return View(MyModelName);
However - why does this also work?:
return View():
Why aren't I required to pass the invalid model back explicitly? Even this doesn't pass a blank model back to the view:
return View(new MyModelName());
I have to execute:
ModelState.Clear();
To get a blank model to the view. Can somebody explain to me why it behaves like this so I can understand what is going on.
I can find nothing on Google about this. Thanks.
Because it checks the ModelState dictionary first to see any values are there. If yes, those will be used to render the values for input fields of your form.
When you call ModelState.Clear(), It clears the model state dictionary. Since the model state dictionary is empty, now it will fallback to the model passed to the view and use that. That is the reason you will be able to see any updated property value of your view model in the view, If you update a property value in your action method and return to view.
I've had a thorough search around but really can't find anything addressing the scenario I'm facing (oddly because I'd have thought it's quite a common thing to do).
Background
I'm creating an application with ASP.NET MVC 4 and Entity Framework 5 Code First. For the purpose of this question, think of it as a blogging application with posts and users.
Project
The post model requires that every post have a corresponding UserId.
With the ASP.NET MVC 4 Membership it is easy to find the username of the person logged in with
User.Identity.Name.
This isn't ideal, we want the ID, but a query such as this can search the db for the name and get the ID.
db.UserProfiles.Single(a => a.UserName == User.Identity.Name);
Problem
The problem arises when trying to create a post. Model.IsValid is false, as no UserId is being passed in from the view. Obviously, as the user isn't expected to enter their ID.
I've tried putting the ID value into the ViewBag and using a #Html.Hidden() field in the view, however I've had no success with this. Model.IsValid always returns false.
Should this information be input through the create view? Or should it be done directly in the controller? Its quite a frustrating problem as I have the information and just need to figure how to pass it into the model.
CONTROLLER CODE
This is basically just the default scaffolded code. The commented code is how I tried setting the model value directly from the controller, however that was little more than trial and error.
//
// POST: /Post/Create
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(Post post)
{
if (ModelState.IsValid)
{
//var userId = db.UserProfiles.Single(a => a.UserName == User.Identity.Name);
//post.User.UserId = userId.UserId;
db.Posts.Add(post);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(post);
}
Be careful with hidden fields. Anyone could put whatever value they want in that field (i.e. they could spoof another user). You'd be better off caching the ID in the session at login, and using that value.
This is a typical case where you want to create an EditModel as a data transfer object (DTO) between your view and controller layers.
Create a class BlogPostEditModel that has all properties you need the user to fill in when creating a new blog post. Then, map this type (e.g. using AutoMapper) to your BlogPost entity, and fill in the user ID as well.
To use built-in validation such as Model.IsValid(), put the data annotations attributes on the DTO instead.
Honestly, I would have the value assigned via the controller. If you had someone messing with your html via Firebug, they could actually change the id before it was passed and submitted to your form. I would remove it from your Create view and submit from the controller.
Is it possible to disable a certain action parameter from retaining its value across requests?
[HttpPost]
public ActionResult MyAction(string value1, string value2)
{
if(value1=="hi")
ModelState.AddModelError("value1", "Can't have hi");
//do stuff
if(ModelState.IsValid)
return RedirectToAction("Finish");
else
return View()
}
[HttpGet]
public ActionResult MyAction()
{
return View()
}
The view consists of a simple form with two input boxes (value1 and value2). Once submitted and validation fails, the view is returned. I want to always have the value of the textbox in the view to be empty.
The value for the textbox "value1" is retained if the the model is invalidated.
I tried to declare the textbox as <%= Html.TextBox("value1", null) %> but the value is still retained. I also tried to use [Bind(Exclude="value1")] but that dosen't work on a single variable.
Update 2:
I'm doing this for a textbox that is used for Captcha (custom solution) input. I want the textbox to be cleared any time the page is loaded, but I want validation to remain.
Try calling
ModelState["value1"].Value
= new ValueProviderResult(null, string.Empty, CultureInfo.InvariantCulture);
before you return the view from within your controller action.
What this does is keep all the errors associated with the key "value1", but replaces the value with an empty value.
What are you doing that's causing it to be retained? There isn't anything like ViewState in MVC that will persist a value over multiple requests unless you're writing code or using form fields to make it do so.
What does the view look like? Is this action method being called via GET or POST? What's the "do stuff" contained in your method?
Edit: You're still showing //do stuff in your example code. Does that stuff contain any references to ViewData? Your question is about binding, but I don't see any binding happening. Maybe this is beyond my understanding.
Edit 2: Glad Phil saw this one! The original question didn't mention the ModelState.
After a user clicks the submit button of my page, there is a textbox that is validated, and if it's invalid, I show an error message using the ModelState.AddModelError method. And I need to replace the value of this textbox and show the page with the error messages back to the user.
The problem is that I can't change the value of the textbox, I'm trying to do ViewData["textbox"] = "new value"; but it is ignored...
How can I do this?
thanks
You can use ModelState.Remove(nameOfProperty) like:
ModelState.Remove("CustomerId");
model.CustomerId = 123;
return View(model);
This will work.
I didn't know the answer as well, checked around the ModelState object and found:
ModelState.SetModelValue()
My model has a Name property which I check, if it is invalid this happens:
ModelState.AddModelError("Name", "Name is required.");
ModelState.SetModelValue("Name", new ValueProviderResult("Some string",string.Empty,new CultureInfo("en-US")));
This worked for me.
I have a situation where I want to persist a hidden value between POST's to the controller. The hidden value is modified as other values are changed. I couldn't get the hidden element to update without updating the value manually in ModelState.
I didn't like this approach as it felt odd to not be using a strongly typed reference to Model value.
I found that calling ModelState.Clear directly before returning the View result worked for me. It seemed to then pick the value up from the Model rather than the values that were submitted in the previous POST.
I think there will likely be a problem with this approach for situations when using Errors within the ModelState, but my scenario does not use Model Errors.
I have a View class (OrderView.aspx) which shows the details of an order (Account Name, Order Date) as well as a list of order lines via the Repeater control. Each order line is represented by a User Control View (OrderLineView.ascx) which shows the details of the order line (Item Name, Quantity, Price). I have a model object called Order which I use as the data source for all of this, which I pass as the model object for the view.
Each OrderLineView user control has a Save and a Delete button. I have the Save button posting the contents of a form within the OrderLine control to a Save method on the Controller and then RedirectToAction back to the same Order page (this refreshes the whole page, nothing AJAXy about it). I have the Delete button linking to a method on the Controller that tries to delete, and then RedirectToAction back to the same Order page. If the delete fails, however, I want a little error message to show up next to the delete button when the page renders again(remember, there is a delete button for every order line on the page, so I only want the message next to the one I clicked). My questions:
1 - How do I pass this data from my Controller method to the specific User Control? Should I somehow add it in to the model? Seems like a bad idea (since it really isn't part of the model).
2 - Should I have a OrderLineController for the OrderLine operations as well as a OrderController for Order operations? I just want to know if best practice is to have a separate Controller for every view.
3 - I have seen how some people might call RedirectToAction with an anonymous type value like this:
RedirectToAction("ViewOrder", new { Id = 1234, Message = "blabla"});
but this makes the Message value show up in the URL string. I am OK with that, but would prefer that it doesn't show if possible.
4 - Also, for accessing properties of the Model from within the view, I find myself doing this all of the time:
foo(((someModelType) this.ViewData.Model).SomeProperty);
I don't like this for a number of reasons, one of which is the fact that I don't want my view to be coupled with the type of my model (which is why I am using ViewPage instead of ViewPage). I would much prefer to be able to have a call like this:
foo(ModelEval("SomeProperty"));
Is there such a thing? I have written my own, but would like it if I didn't have to.
1
Check out ModelState.
ViewData.ModelState.AddModelError("something.Name", "Please enter a valid Name");
ModelState is actually a dictionary, so you could identify the errors on a per-control basis. I don't know if this is a best practice, but it would probably work.
Try something along the lines of
ViewData.ModelState.AddModelError("something#3.Name", "Please enter a valid Name");
and in your view, you could put
<%= Html.ValidationMessage(string.format({"something{0}.Name", YourUniqueId))%>
4
You can strongly type your view, so you don't need that cast, but if you're concerned about tightly coupling, this may put you off. But having the strong type there is no more tightly coupled than having a magic string point to that property of the model anyway. The former just gives you type safety and the glory that is intellisense.
Since your OrderLine has a unique ID you can use that to construct a key to be placed in the ModelState errors container.
public ActionResult Delete(int? Id)
{
ModelState.AddModelError("OrderLine" + Id.Value, "Error deleting OrderLine# " + Id.Value);
...
}
and then use the ValidatinoMessage helper. This will check the ModelState to see if an error exists and if it does it will display the message. Otherwise it's blank.
<%= Html.ValidationMessage ("OrderLine" + Id)%>
In the next release of MVC Model will become a top level property so the following
foo(((someModelType) this.ViewData.Model).SomeProperty);
can be written as
foo(Model.SomeProperty);
Model objects should already be typed unless you're using public object as a property?