I am having a problem returning values to the controller when using a ViewModel.
For clarity I have simplified the code below where the original has many more fields.
When the page is loaded, the value in the hidden field is as expected. However when the form is submitted the value in the field is not being sent and instead I get an ArgumentNullException.
Please can you advise on what I am doing wrong.
View
#model Project.Models.SCView
#using (Html.BeginForm("ScorecardEdit"))
{
#Html.AntiForgeryToken()
#Html.ValidationSummary(true)
#Html.HiddenFor(model => model.FV.ID)
<input type="submit" value="Save" />
}
Model
public class FixView
{
public int ID { get; set; }
[DisplayFormat(DataFormatString = "{0:ddd dd/MM/yyyy}")]
public DateTime MatchDate { get; set; }
}
public class SCView
{
public FixView FV { get; set; }
public SCView()
{
this.FV = new FixView();
}
}
Controller
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult ScorecardEdit(SCView ReturnSC)
{
}
The code that you have should be working as MVC should be able to map your FV.ID property as expected as the HiddenFor() helper will generate the proper names to handle mapping it :
Using the same code that you provided, the debugger demonstrated the following after submitting the form :
The issue here sounds like you have a few other properties, possibly collection-based ones that use the DropDownListFor() helpers that have collections which are not posted to the server, so when you attempt to use the model you have to render populate one of those helpers, you are getting your ArgumentNullException.
Related
I am trying to send data from a view to a controller Create method. But the view model parameter is getting null values when the create method is called.
In my view I want to add a item and show a list of added items.
I have tried to send data to the create method but its view model parameter is getting null values.
In the following code whenever Create method is hit the value of p.posts and p.post is null. How can I get the value of p.post and p.posts here?
Controller method
public ActionResult Create(PostsViewModel p) {}
View Model
public class PostsViewModel
{
public IEnumerable<Post> posts;
public Post post;
}
View
#model NotesWebApplication.ViewModels.PostsViewModel
...
#using (Html.BeginForm()) {
...
#Html.EditorFor(model => model.post.postText, new { htmlAttributes = new { #class = "form-control" } })
...
<input type="submit" value="Create" class="btn btn-default" />
Also in my Create method if I wanted to add Bind then which should be added
[Bind(Include="postText")]
or
[Bind(Include="post.postText")]
update
I made the following changes in PostsViewModel class
public class PostsViewModel
{
public IEnumerable<Post> posts { get; set; }
public Post post { get; set; }
}
and the Create method in the controller is changed to
[HttpPost]
public ActionResult Create([Bind(Include="post, posts")]PostsViewModel p) {}
This is what the httpget Create method looks like
// GET: Posts/Create
public ActionResult Create()
{
PostsViewModel postsViewModel = new PostsViewModel();
postsViewModel.posts = db.Posts;
postsViewModel.post = new Post();
return View(postsViewModel);
}
Now when I submit the form p.post in the controller parameter receives the desired value. But p.posts remains null. Why is this hapenning?
I guess the reason is u don`t have an instance of your post object. Try to make your viewModel something like this:
public class PostsViewModel
{
public string PostText {get;set;} // don`t forget to make it like property, not just a field
}
and then create an instance in your controller:
public ActionResult Create(PostsViewModel p)
{
Post post = new Post{ postText = p.PostText};
//and do what you want with it
}
I've got a viewmodel that contains other viewmodels.
public class AggregateVM
{
public BrandVM BrandVM { get; set; }
public TinTypeVM TinTypeVM { get; set; }
}
When I http post to the controller action, the TinTypeVM is populated with my edited values, but the BrandVM viewmodel where I used a partial is always null.
Here's are the view.
#model SaveEF.ViewModels.AggregateVM
#using (Html.BeginForm("EditAggregate", "Aggregate"))
{
#Html.Partial("_EditBrand", Model.BrandVM)
#Html.Label("Tin Name")
#Html.EditorFor(model => model.TinTypeVM.Name)
<input type="submit" value="Save" />
}
Here's the partial view.
#model SaveEF.ViewModels.BrandVM
#Html.Label("Brand Name")
#Html.EditorFor(model => model.Name)
Here's the controller action.
public ActionResult EditAggregate(AggregateVM vm)
{
SaveBrand(vm.BrandVM);
SaveTinType(vm.TinTypeVM);
return RedirectToAction("Index");
}
How can I use partials in the view and still pass a single view model into the EditAggregate action? I've tried different parameters in Html.BeginForm("EditAggregate", "Aggregate", FormMethod.Post, new { vm = Model })) but that didn't help.
Short Answer
You need to pass AggregateVM to your partial too.
Long Answer
The way you are doing it right now is:
#model SaveEF.ViewModels.BrandVM
#Html.EditorFor(model => model.Name)
So if you were to inspect the name generated for the editor would be Name. Thus when you post, the default model binder of MVC will look for a matching property in your view model. But you view model is like this:
public class AggregateVM
{
public BrandVM BrandVM { get; set; }
public TinTypeVM TinTypeVM { get; set; }
}
And there is no Name property.
Fix
You need to pass AggregateVM to your partial too.
#model SaveEF.ViewModels.AggregateVM
#Html.EditorFor(model => model.BrandVM.Name)
and now the name for the editor will be BrandVM.Name. So when you post, the default model binder will look for the property BrandVM.Name and find it. Thus it will populate it.
The other alternative is to specify the name attribute yourself by using #Html.Editor or pass the attribute.
I have a ViewModel that has a complex object as one of its members. The complex object has 4 properties (all strings). I'm trying to create a re-usable partial view where I can pass in the complex object and have it generate the html with html helpers for its properties. That's all working great. However, when I submit the form, the model binder isn't mapping the values back to the ViewModel's member so I don't get anything back on the server side. How can I read the values a user types into the html helpers for the complex object.
ViewModel
public class MyViewModel
{
public string SomeProperty { get; set; }
public MyComplexModel ComplexModel { get; set; }
}
MyComplexModel
public class MyComplexModel
{
public int id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
....
}
Controller
public class MyController : Controller
{
public ActionResult Index()
{
MyViewModel model = new MyViewModel();
model.ComplexModel = new MyComplexModel();
model.ComplexModel.id = 15;
return View(model);
}
[HttpPost]
public ActionResult Index(MyViewModel model)
{
// model here never has my nested model populated in the partial view
return View(model);
}
}
View
#using(Html.BeginForm("Index", "MyController", FormMethod.Post))
{
....
#Html.Partial("MyPartialView", Model.ComplexModel)
}
Partial View
#model my.path.to.namespace.MyComplexModel
#Html.TextBoxFor(m => m.Name)
...
how can I bind this data on form submission so that the parent model contains the data entered on the web form from the partial view?
thanks
EDIT: I've figured out that I need to prepend "ComplexModel." to all of my control's names in the partial view (textboxes) so that it maps to the nested object, but I can't pass the ViewModel type to the partial view to get that extra layer because it needs to be generic to accept several ViewModel types. I could just rewrite the name attribute with javascript, but that seems overly ghetto to me. How else can I do this?
EDIT 2: I can statically set the name attribute with new { Name="ComplexModel.Name" } so I think I'm in business unless someone has a better method?
You can pass the prefix to the partial using
#Html.Partial("MyPartialView", Model.ComplexModel,
new ViewDataDictionary { TemplateInfo = new TemplateInfo { HtmlFieldPrefix = "ComplexModel" }})
which will perpend the prefix to you controls name attribute so that <input name="Name" ../> will become <input name="ComplexModel.Name" ../> and correctly bind to typeof MyViewModel on post back
Edit
To make it a little easier, you can encapsulate this in a html helper
public static MvcHtmlString PartialFor<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression, string partialViewName)
{
string name = ExpressionHelper.GetExpressionText(expression);
object model = ModelMetadata.FromLambdaExpression(expression, helper.ViewData).Model;
var viewData = new ViewDataDictionary(helper.ViewData)
{
TemplateInfo = new System.Web.Mvc.TemplateInfo
{
HtmlFieldPrefix = string.IsNullOrEmpty(helper.ViewData.TemplateInfo.HtmlFieldPrefix) ?
name : $"{helper.ViewData.TemplateInfo.HtmlFieldPrefix}.{name}"
}
};
return helper.Partial(partialViewName, model, viewData);
}
and use it as
#Html.PartialFor(m => m.ComplexModel, "MyPartialView")
If you use tag helpers, the partial tag helper accepts a for attribute, which does what you expect.
<partial name="MyPartialView" for="ComplexModel" />
Using the for attribute, rather than the typical model attribute, will cause all of the form fields within the partial to be named with the ComplexModel. prefix.
You can try passing the ViewModel to the partial.
#model my.path.to.namespace.MyViewModel
#Html.TextBoxFor(m => m.ComplexModel.Name)
Edit
You can create a base model and push the complex model in there and pass the based model to the partial.
public class MyViewModel :BaseModel
{
public string SomeProperty { get; set; }
}
public class MyViewModel2 :BaseModel
{
public string SomeProperty2 { get; set; }
}
public class BaseModel
{
public MyComplexModel ComplexModel { get; set; }
}
public class MyComplexModel
{
public int id { get; set; }
public string Name { get; set; }
...
}
Then your partial will be like below :
#model my.path.to.namespace.BaseModel
#Html.TextBoxFor(m => m.ComplexModel.Name)
If this is not an acceptable solution, you may have to think in terms of overriding the model binder. You can read about that here.
I came across the same situation and with the help of such informative posts changed my partial code to have prefix on generated in input elements generated by partial view
I have used Html.partial helper giving partialview name and object of ModelType and an instance of ViewDataDictionary object with Html Field Prefix to constructor of Html.partial.
This results in GET request of "xyz url" of "Main view" and rendering partial view inside it with input elements generated with prefix e.g. earlier Name="Title" now becomes Name="MySubType.Title" in respective HTML element and same for rest of the form input elements.
The problem occurred when POST request is made to "xyz url", expecting the Form which is filled in gets saved in to my database. But the MVC Modelbinder didn't bind my POSTed model data with form values filled in and also ModelState is also lost. The model in viewdata was also coming to null.
Finally I tried to update model data in Posted form using TryUppdateModel method which takes model instance and html prefix which was passed earlier to partial view,and can see now model is bound with values and model state is also present.
Please let me know if this approach is fine or bit diversified!
I have an experience in work with ASP.NET forms, but new to MVC.
How can I get data from shared views on postback?
In ASP.NET Forms I can write something like this:
ASP.NET Forms:
Model code:
public class MyModelItem
{
// Just TextBox is enough for editing this
public string SimpleProperty { get; set; }
// For this property separate NestedItemEditor.ascx is required
public MyModelNestedItem ComplexProperty { get; set; }
}
public class MyModelNestedItem
{
public string FirstProperty { get; set; }
public string SecondProperty { get; set; }
}
Behavior:
Control for editing MyModelNestedItem is separate ASCX control NestedItemEditor.ascx
This is just for example, MyModelNestedItem can be much more complex, I just want to give idea what I mean.
Now when I showing this item for editing, I'm showing one asp:TextBox and one NestedItemEditor.ascx. On page postback I'm gathering data from both and that's it.
Problem with MVC:
When I'm trying to implement this scenario with MVC, I'm using customized EditorFor (through using UIHint and creating shared view). So this shared view Views\Shared\EditorTemplates\MyModelNestedItem.cshtml can now display data that is already in MyModelNestedItem property but I have no idea how to make it return new entered data.
When parent controller recieves a post request, data seems to be in Request.Form, but which is civilized way to reach it? Sure, the best solution will be if data will fetch automatically into the MyModelItem.ComplexProperty.
The action which is called on post needs to be something like:
[HttpPost]
public ActionResult Index(MyViewModel mdl)
Then all the properties of the model which have input controls (or hidden inputs) on the form will have the data which was entered on the form (or passed to it or modified by javascript, in the case of hidden inputs).
This assumes that MyViewModel is the model referenced in your view.
Writing an ActionResult method in the controller with the complex type simply worked for me:
public class Topic
{
public Topic()
{
}
public DetailsClass Details
{
get;
set;
}
}
public class DetailsClass
{
public string TopicDetails
{
get;
set;
}
}
The view:
#modelTopic
#using (Html.BeginForm("Submit","Default"))
{
#Html.EditorFor(m=>m.Details)
#:<input type="submit" />
}
The controller:
public ActionResult Index()
{
Topic topic = new Topic();
return View( topic);
}
public ActionResult Submit(Topic t)
{
return View(t);
}
When submited, the Topic t contains the value i ented within the editor (Assuming You have a custom editor for the complex type, DetailsClass in my sample)
For example:
class MyContoller
{
[MyCustomAttribute]
public ActionResult MyAction(ModelX fromRequest, ModelY fromSession, ModelZ fromCookie)
{
string productId = fromRequest.ProductId;
string userId = fromSession.UserId;
string cultureName = fromCookie.CultureName;
}
}
Reason:
I don't want to visit Request, Session and HttpContext in the controllers, and the default idea of MVC3 which passing models to actions is very great.
I want the number of parameters of MyAction is easy to change. For example, if I add a new parameter, the system will try to look for values in Request, Session or Cookies by the name or type of the parameter (I think custom ModelBinders may be required for cookie values) and pass the filled model to my action. I don't have to write extra code.
Can the custom attribute (MyCustomAttribute in the example) accomplish this idea?
I am not sure I follow you about the custom attribute. What are you expecting the custom attribute to do?
Yes, an action method can take as many model parameters as you want. Obviously, only one can be bound in any given request (because a view can only have one model). Whichever one is found first will be bound, and the others will be null.
So let's say you have the following:
public class ModelX {
public string X {get;set;}
}
public class ModelY {
public string Y {get;set;}
}
public class ModelZ {
public string Z {get;set;}
}
And you have an action method like this:
public ActionResult DoIt(ModelX x, ModelY y, ModelZ z)
{
return View();
}
And in your DoIt.cshtml you have the following:
#model ModelZ
#using(Html.BeginForm()) {
#Html.TextBoxFor(x => x.Z)
<input type="submit"/>
}
If you type something into the textbox and submit, then the model binder will bind a ModelZ with the value you entered and ModelX and ModelY will be null.
If you mean can an action method bind multiple models simultaneously, then I would have to ask you.. How exactly do you plan to have a view have more than one model? You can certainly create a wrapper model to contain the multiple models, but a view can only have one.
Create a composite ViewModel class that incorporates ModelX, ModelY and ModelZ. You can then populate an instance of your new ViewModel class, and pass that to your controller method.
public class XYZViewModel
{
public ModelX fromRequest { get; set; }
public ModelY fromSession { get; set; }
public ModelZ fromCookie { get; set; }
}
public class MyController
{
[MyCustomAttribute]
public ActionResult MyAction(XYZViewModel myModel)
{
string productId = myModel.fromRequest.ProductId;
string userId = myModel.fromSession.UserId;
string cultureName = myModel.fromCookie.CultureName;
}
}
You can always pass multiple parameters to your controller action, yes. The key is to make sure they are properly serialized in the request. If you're using a form, that means using the Html helper methods.
For example, let's say you want an action like this:
public ActionResult Multiple(ModelA a, ModelB b)
{
// ...
}
You could create simple partial view for each model:
#model MyProject.Models.ModelA
#Html.EditorForModel()
Then in your Multiple view, render the partial views like so:
#{ using (Html.BeginForm("Multiple", "MyController", FormMethod.Get))
{
#Html.Partial("A", new MyProject.Models.ModelA())
#Html.Partial("B", new MyProject.Models.ModelB())
<input type='submit' value='submit' />
}
I set the method to GET here so that you can easily see how MVC passes the parameters. If you submit the form, you'll see that MVC successfully deserializes each object.