I have a form which needs to populate 2 models. Normally I use a ModelBinderAttribute on the forms post action i.e.
[Authorize]
[AcceptVerbs("POST")]
public ActionResult Add([GigBinderAttribute]Gig gig, FormCollection formCollection)
{
///Do stuff
}
In my form, the fields are named the same as the models properties...
However in this case I have 2 different models that need populating.
How do I do this? Any ideas? Is it possible?
Actually... the best way is to do this:
public ActionResult Add([GigBinderAttribute]Gig gig, [FileModelBinderAttribute]File file) {
}
You CAN use multiple attributes!
In cases like this, I tend to make a single model type to wrap up the various models involved:
class AddModel
{
public Gig GigModel {get; set;}
public OtherType OtherModel {get; set;}
}
...and bind that.
The UpdateModel or TryUpdateModel method can be used to do this. You can pass through the model, the model you wish to bind, the prefix of the items you wish to bind to that model and the form. For example if your Item model has form variables of "Item.Value" then your update model method would be:
UpdateMode(modelObject, stringPrefix, formCollection);
If you're using the entity framework, it's worth pointing out that the UpdateModel method doesn't always work under some conditions. It does work particularly well with POCOs though.
Related
For a project I'm currently working on, I currently have 2 separate instances of users (might increase later): CorporateCustomer and PrivateCustomer.
Both inherit from the abstract class Customer.
To display the differences between these customers, currently 2 different views are created, which are rendered by the same Action in the following way:
[HttpGet]
public virtual ActionResult Edit()
{
if(User.IsCorporate)
return View("EditCorporate", new CorporateCustomer());
else
return View("EditPrivate", new PrivateCustomer());
}
[HttpPost]
public virtual ActionResult Edit(CorporateCustomer customer){...}
[HttpPost]
public virtual ActionResult Edit(PrivateCustomer customer){...}
For just displaying information, this works like a charm. The urls are the same for each type, which is what we were aiming for.
However, when doing a post, I can only specify a single type, or risk running into an ambiguous action method (which makes sense, of course).
Now my question is: is there any elegant way to handle these 2 different types, while still retaining a single url? Or am I doomed to make the base class non-abstract and look up the values in the Request.Form collection?
Thanks if anyone can come up with a sollution (or just straight point out that what I'm doing is stupid and cannot be done)
You could have one Action that takes both parameter types.
The model binder should then fill them with whatever data is posted and you can figure out which is right in your Action method.
[HttpPost]
public virtual ActionResult Edit( CorporateCustomer c, PrivateCustomer p )
{
...
}
I am working on an MVC 4 site that makes extensive use of partial views. On one page, however, I am using the the same partial view within nested partial views and my Model is nested as well. I checked it out in Fiddler, and the data is being posted as part of the form. When it hits my break point that I've set up in the action method of the controller those nested view models are coming in as null. I've tried using editor templates instead of partial views, but I had no luck on that one.
Has anyone experienced this behavior before, and is so, do you have any ideas as to what might be causing it?
I have had this same problem before because I accidentally passed a nested ViewModel property into my partial page.
If you are nesting partials you need to be careful about how you are passing in your model, for example:
Lets say this is your ViewModel:
public class Person
{
public string Name {get; set;}
public Address Address {get; set;}
}
public class Address
{
public string Line1 {get; set;}
//etc
}
And your controller action:
public ActionResult UpdatePerson(Person p)
{
}
If you have a separate view to display an Address make sure you do it like this:
#Html.RenderPartial("Address", Model)
And not like this:
#Html.RenderPartial("Address", Model.Address)
If you do the second example the name of the "TextboxFor" inputs will be named incorrectly for the model binder to be able to understand.
Another option would be to call out address specifically in your controller action like this to allow the model binder to see the address properly:
public ActionResult UpdatePerson(Person p, Address addr)
{
}
Working with ViewModels, I would like to split them:
public SignUpViewModel //for display
{
public SignUpUserViewModel SignUpUserViewModel { get; set; } //for validation
public IEnumerable<SelectListItem> UserTypes {get;set;}
}
So I want to render SignUpViewModel but get SignUpUserViewModel as an argument of POST-action.
Do you find this reasonable? What are the ways to implement this approach?
Looks like DefaultModelBinder doesn't work this way: it doens't understand SignUpUserViewModel is a property of SignUpViewModel. So one way I see is to implement custom model binder. Any other?
I think that's reasonable. Just have your post action bind to the SignUpUserViewModel.
E.g.
[HttpPost]
public ActionResult Edit(int id, SignUpUserViewModel editForm)
On a side note, looking at your SignUpViewModel vs SignUpUserViewModel, I think you could just combine them into the one view model.
In saying that I will say that I too sometimes have a similar setup to what you have, e.g. ViewModel and a child FormModel (posting and binding to the FormModel) but I put anything to do with the form like validation and the SelectListItems in the FormModel. So in your case above, I would just combine them into the one FormModel.
I have a controller with typical create methods (one for GET, one for POST). the POST takes a strongly-typed parameter:
[HttpPost] public ActionResult Create(Quiz entity)
however, when the callback is made, the properties of my entity are null... if I redefine it like this:
[HttpPost] public ActionResult Create(Quiz entity, FormCollection form)
I can see that the values are there e.g. form["Component"] contains "1". I've not had this problem in the past and I can't figure out why this class would be different.
thoughts anyone?
The easiest way to get the default model binder to instantiate Quiz for you on postback is to use the Html form helpers in you view. So, for example, if your Quiz class looked like this:
public class Quiz
{
public int Id { get; set; }
public string Name { get; set; }
}
The following code in your view would ensure the values are present on postback:
#Html.HiddenFor(mod => mod.Id)
#Html.TextBoxFor(mod => mod.Name)
Keep in mind that values which need to be posted back but not shown in the view (like identifiers) need to be added to the view with Html.HiddenFor.
Here's a more comprehensive list of Html form helper functions.
I FIGURED IT OUT!!
so, in my model (see comments on #ataddeini's thread below) you can see I have a Component... to represent components I used a couple of listboxes, the second (Components) dependent on the contents of the first (Products). In generating the second list I used
#Html.DropDownListFor(x => x.Component, ...)
which (as shown in one of the above links) generates a form field called "Component"... and therein lies the problem. What I needed to have done is bind it to the the Id of the component instead!
#Html.DropDowListFor(x => x.Component.Id, ...)
hurray!
Suppose I want to allow to select our entity (from a dropdown, etc) on a page, let's say Product. As a result I may receive this:
public ActionResult SelectedAction(Guid productId)
{
}
But, I want to use model binders power, so instead I write model binder to get my product from repository and instead use
public ActionResult SelectedAction(Product product)
{
if (ModelState.IsValid) {} else {}
}
My model binder will set model state to false if product is invalid.
Now, there're problems with this approach:
It's not always easy to use strongly-typed methods like Html.ActionLink(c => c.SelectedAction(id)) since we need to pass Product, not id.
It's not good to use entities as controller parameters, anyway.
If model state is invalid, and I want to redirect back and show error, I can't preserve selected product! Because bound product is not set and my id is not there. I'd like to do RedirectToAction(c => c.Redisplay(product)) but of course this is not possible.
Now, seems like I'm back to use "Guid productId" as parameter... However, there's one solution that I'd like to present and discuss.
public class EntityViewModel<T> where T : BaseEntity
{
public EntityViewModel(Guid id)
{
this.Id = id;
}
public static implicit operator EntityViewModel<T>(T entity)
{
return new EntityViewModel<T>(entity.Id);
}
public override string ToString()
{
return Id.ToString();
}
public Guid Id { get; set; }
public T Instance { get; set; }
}
Now, if I use
public ActionResult SelectedAction(EntityViewModel<Product> product)
{
if (ModelState.IsValid) {} else {}
}
all the problems are solved:
I can pass EntityViewModel with only Id set if I have only Id.
I don't use entity as parameter. Moreover, I
can use EntityViewModel as property inside another ViewModel.
I can pass EntityViewModel back to RedirectToController and it will keep its Id value, which will be
redisplayed to user along with the validation messages (thanks to MVCContrib and ModelStateToTempData / PassParametersDuringRedirect).
The model binder will get Instance from the repository and will set model state errors like "Not found in database" and so on. And I can use things like ActionLink(c => c.Action(Model.MyProductViewModelProperty)).
The question is, are there any drawbacks here? I can't see anything bad but I'm still new to MVC and may miss some important things. Maybe there're better and approved ways? Maybe this is why everybody uses entity IDs as input parameters and properties?
Overall that looks like a good appoach to me...
As an alternative, you could use POCO for your viewmodel then I think all 3 problems would be solved automatically. Have you seen the Automapper project that allows an Entity to DTO approach? This would give you more flexibility by separating you ViewModel from your EntityModel, but really depends on the complexity of you application you are building.
MVC's ViewDataExtensions might also be useful instead of creating custom containers to hold various viewmodel objects as you mention in number 2.
MVCContrib's ModelStateToTempData should work for any serializable object (must be serializable for any out of process sessionstate providers eg. SQL, Velocity etc.), so you could use that even without wrapping your entity classes couldn't you?