MVVM and ModelBinders in the ASP.NET MVC Framework - asp.net-mvc

I've got a series of views, each are typed to have their own ViewModel class which contains everything they need to display themselves, for example:
public class CreateResourceViewModel
{
public Project Parent { get; set; }
public SelectList Categories { get; set; }
public Resource Resource { get; set; }
}
The post action method for this I'd like to use would look like this:
[AcceptVerbs (HttpVerbs.Post)]
public ActionResult Create (Resource resource)
{
// Update code...
}
Notice that the only object I'm interested in is the Resource property of the CreateResourceViewModel, not the CreateResourceViewModel itself. Everything else is just gravy for for the user, what they're updating is the resource class...
Is this possible within the MVC Framework (even if it's v2 CTP)?
Thanks all

Sure. Use:
public ActionResult Create([Bind(Prefix="Resource")]Resource resource)

Related

MVC - Multiple models in a view

I'm using MVC (for the first time) with Entity framework, Database first
What I want to do is display data from a database in a single view. I created the database first, then I made a ADO.NET Entity Data Model based from the database that contains all the tables. I then created a Index view that was strongly typed with my Entity Data Model as model.
In my Index I have at the top
#model IEnumerable<Forum6.Models.Forum>
This allows me to get the rows from the table "Forum" from my database. If I try to add an extra model I get I get this error message when I run:
Line 1: #model IEnumerable<Forum6.Models.Forum>
Line 2: #model2 IEnumerable<Forum6.Models.Post>
Parser Error Message: Only one 'model' statement is allowed in a file.
After searching for an answer I found this: Two models in one view in ASP MVC 3
The answer was to create a ViewModel (ParentModel) that contained all the Models (Tables).
This is the ViewModel I created:
public class ViewModel
{
public IEnumerable<Forum6.Models.Forum> Forum { get; set; }
public IEnumerable<Forum6.Models.Post> Post { get; set; }
public IEnumerable<Forum6.Models.Topics> Topics { get; set; }
public IEnumerable<Forum6.Models.Users> Users { get; set; }
public IEnumerable<Forum6.Models.PrivMsg> PrivMsg { get; set; }
public IEnumerable<Forum6.Models.Permission> Permission { get; set; }
}
I edited my controller to look like this:
public class HomeController : Controller
{
// ForumDBEntities old_db = new ForumDBEntities();
ViewModel db = new ViewModel();
public ActionResult Index()
{
return View(db);
}
}
Then replaced the old Index view with a new strongly typed view that used the ViewModel as model. Which contains:
#model IEnumerable<Forum6.Models.ViewModel>
Trying to run this gives me this error:
The model item passed into the dictionary is of type 'Forum6.Models.ViewModel', but this dictionary requires a model item
of type
'System.Collections.Generic.IEnumerable`1[Forum6.Models.ViewModel]
How do I make the "ViewModel" enumarable? Or is my error elsewhere?
You'll need to change #model IEnumerable<Forum6.Models.ViewModel> to #model Forum6.Models.ViewModel as you're wrapping your IEnumerables inside a single ViewModel.
A good rule of thumb is to have a 1:1 relationship between your ViewModel and View.
This might be a good read for you: http://lostechies.com/jimmybogard/2009/06/30/how-we-do-mvc-view-models/ (just ignore the automapper part if you don't want to go that route)
You'll also need to put in actual data in your ViewModel since
ViewModel db = new ViewModel();
public ActionResult Index()
{
return View(db);
}
will just give your view an empty ViewModel.
One way to do it would be.
public ActionResult Index()
{
var model = new ViewModel
{
Forum = db.GetForum(),
Post = db.GetPost(),
Topic = you get the idea
};
return View(model);
}
One last thing when naming properties or variables in general you should use the plural verb when it contains a list. So your ViewModel would be.
public class ViewModel
{
public IEnumerable<Forum6.Models.Forum> Forums { get; set; }
public IEnumerable<Forum6.Models.Post> Posts { get; set; }
public IEnumerable<Forum6.Models.Topics> Topics { get; set; }
public IEnumerable<Forum6.Models.Users> Users { get; set; }
public IEnumerable<Forum6.Models.PrivMsg> PrivMsgs { get; set; }
public IEnumerable<Forum6.Models.Permission> Permissions { get; set; }
}
Change #model IEnumerable<Forum6.Models.ViewModel> to #model Forum6.Models.ViewModel as you are passing a single instance of a ViewModel class and not a collection of them.
All your collections are passed in a single instance of a view model.

MVC viewmodel constructors

Is it good practice to populate the models/variables of a viewmodel in the constructor of the viewmodel?
For instance:
public class ProgramViewModel
{
public IEnumerable<Programme> ProgramList { get; set; }
public string QuerystringAgeID { get; set; }
public ProgramViewModel()
{
QuerystringAgeID = HttpContext.Current.Request.QueryString["QuerystringAgeID"];
}
}
Is it good practice to populate the models/variables of a viewmodel in
the constructor of the viewmodel?
It depends.
But with the example you have shown, the answer is no. You have a model binder that is supposed to do that:
public class ProgramViewModel
{
public IEnumerable<Programme> ProgramList { get; set; }
public string QuerystringAgeID { get; set; }
}
and then:
public ActionResult Foo(ProgramViewModel model)
{
// model.QuerystringAgeID will be automatically populated
// with the value of the QuerystringAgeID
// thanks to the default model binder
...
}
In addition to that you should absolutely avoid using HttpContext.Current in an ASP.NET MVC application. Makes your code tied to an ASP.NET context making it impossible to reuse and unit test in isolation. ASP.NET MVC provides you abstractions for this: HttpContextBase, ...

Validate a model in viewmodel?

I wonder if there is a way to validate just one of my models in the viewmodel send it to my action? I use the DataAnnotations as validate rules.
Like the if (!ModelState.IsValid)
let me know if the question is unclear and I will edit for a better explination
EDIT
my viewmodel looks like this
public class CompaniesViewModel
{
public Core.Model.Customer Company { get; set; }
public IEnumerable<SelectListItem> Items { get; set; }
public Core.Model.Meeting Meeting { get; set; }
}
What I want to do in this particular situation is to validate just Customer. I cant do the ModelState.IsValid then all get validated. So how can I do to just validate one of them like customer in this case. Hope this was more clear
There are a number of different ways you can do this. The first is to add a property called IsValid that checks the property. So something like:
public class Company
{
public bool IsValid
{
get { return GetValid() }
}
private bool IsValid()
{
if ( Some check here )
return false;
}
}
[HttpPost]
public ActionResult SomeAction(CompaniesViewModel model)
{
if (model.Company.IsValid)
{
}
}
However a better solution IMO would be just to post the Company to your controller rather than your entire view model. Just because your passing a view model to a view it doesn't mean that you need to post the entire view model back. When you create your HTML form specify only the properties you want to post back to your controller. So for example your controller would become:
[HttpPost]
public ActionResult SomeAction(Company company)
{
if (Model.IsValid)
{
}
}
Now when you check if Model.IsValid it just check company as that is all you've passed back to the controller.
At server side, you can try the ValidateModel(object) method, like in TryValidateModel(CompaniesViewModel.Company).
If you have enabled client sided validation, you need to post only the relevant entity. If you want to post all entities, but you need to validate only one, you can consider the following:
either removing the rules, using javascript ASP .NET MVC Disable Client Side Validation at Per-Field Level
or creating a Data-Transfer-Object, ie a View Model which has NO link to the Model, but reproduces the entities you want with the validation rules you want having applied in this scenario. Of course, then, you'll need in your controller or a model binder some way to bind from your ViewModel to your Model entities.
You can separate Customer Model to another class in your ViewModel and map that in Controller to a existing/new Customer:
public class CompaniesViewModel
{
public Company Company { get; set; }
public IEnumerable<SelectListItem> Items { get; set; }
public Core.Model.Meeting Meeting { get; set; }
}
//Validations for Company go here:
public class Company
{
public string CompanyId { get; set; }
[Required]
public string CompanyName { get; set; }
}

Generic data input form in asp.net mvc application

I have an application that have EF 16 classes that share this information: They all are classes only with a key field and a description.
I think it should be a waste if I make a controller with just 1 method just to present a form to fill these classes info, then I was thinking in to make a generic form(with key, description) and dynamically fill the right class through a sort of selection the selected info in any way, any good suggestion or pattern to do that? Where the generic methods should be located.
Have you looked into MVC templates? You should be able to use templates to automatically "generate" your Edit and Display Views. No need to create a distinct View for each of your classes.
I had similar situation and did it almost like that:
interface IKeyDescription
{
int Key { get; set; }
string Description { get; set; }
}
public partial class Class1 : IKeyDescription;
public partial class Class2 : IKeyDescription;
public abstract class BaseKeyDescriptionController<T> where T : IKeyDescription
{
[Inject]
public IKeyDescriptionService<T> Service { get; set; }
[HttpGet]
public ActionResult List()
{
//View is stored in shared folder
return View("List",Service.List());
}
[HttpPost]
public ActionResult List(IList<T> elements)
{
Service.Save(elements);
....
}
}
public class Class1Controller : BaseKeyDescriptionController<Class1>
{
}
public class Class2Controller : BaseKeyDescriptionController<Class2>
{
}
View will inherit from System.Web.Mvc.ViewPage<IKeyDescription>.

Passing complex object from view to controller/view in ASP.NET MVC

In my MVC application I have a problem with passing data from view to controller. I have fairly complex domain classes:
public class TaskBase : PersistableObject
{
public virtual TaskCategory Category { get; set; }
public virtual IList<TaskNote> Notes { get; set; }
public virtual string TaskTitle { get; set; }
public virtual string TaskBody { get; set; }
public virtual DateTime? CreationTime { get; set; }
public virtual User CreatedBy { get; set; }
public virtual int CompletionRatio { get; set; }
}
public class MainTask : TaskBase
{
public virtual IList<TaskBase> ChildTasks { get; set; }
public virtual User AssignedTo { get; set; }
public virtual IList<TaskHistory> History { get; set; }
}
public class TaskFormModel : ViewDomainBase
{
public MainTask Task { get; set; }
public LoginForm LoginInfo { get; set; }
}
And in my view I want to pass an instance of TaskFormModel to the controller.
<%= Html.ActionLink<TaskController>("Edit Task", (x) => x.Edit(new TaskFormModel() { Task = item, LoginInfo = Model.LoginInfo }))%>
And here is the controller action:
public ActionResult Edit (TaskFormModel taskInfo)
{
return View(ViewPageName.TaskDetailsForm, task.Task);
}
In this action method taskInfo comes null even if I pass non-null instance from view. I think I have a binding problem here. I think, writing custom model binder requires every property to be converted and also when new fields added then binder class should also be changed, so I don't want custom model binder to do this. Is there any other way to pass data to controller in this scenario? Or could custom model binder can be coded so that less code written and also when new properies are added binder class will not need to be changed?
Edit After Comments: What I am trying to achieve is basically to pass an instance from one view to another view, without querying repository/db in my controller's action.
First version of answer:
Your GET edit method should be like:
public ActionResult Edit (int id)
{
var model = taskRepository.GetTaskEditModel(id);
return View(ViewPageName.TaskDetailsForm, model);
}
and ActionLink:
<%= Html.ActionLink("Edit Task", "Edit", "Task", new { model.Task.id })%>
If you want to pass complex objects to controller, you should wrap them up in html form and pass to POST action.
In my opinion you are doing something wrong.
As I understand: you are trying to instantiate a new object, pass it to browser and get it back.
well you cant.
If object you want to edit exists already in your storage, then you should alter your ActionLink to reference it by id, and instantiate it inside your Edit action.
Take a look at default strongly typed index views created by tooling.

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