I'm trying to understand MVC.
Let's say on the View I have a checkbox, we'll call it 'checkBox1'...
In my Controller, can I access this checkbox directly?
Can I go:
checkBox1.Checked = true
??
A controller cannot directly access the elements of a view as it has no information about it. A controller can only act as a point of control to regulate data between the views and models. However you can manipulate the views from the controller like loading a specific view template or rendering a chunk of code ( in case of xhr request) to the output. But once it renders that it will not have any information about the individual elements of the view.
Take a look at this
http://www.enode.com/x/markup/tutorial/mvc.html
No. The controller deals with the data (model) sent to and from the view and is deliberately separated from the details of the View.
I suggest spending some time reading up on the basics of ASP.NET MVC and doing some tutorials on the ASP.NET MVC site
Read here for details on handling checkboxes...
CheckboxList in MVC3.0
Related
I am a learner in MVC, I am facing a issue in passing data, I want to pass a data from one view to another view in MVC, How can I do this? help me,
I will select the firstname in one view and I want to pass the firstname to another view?
Views don't communicate with other views.
Consider this illustration from the Wikipedia page:
A view doesn't connect to another view. It is simply an interface presented to the user. Data which originates in a view (such as user input) would then be passed to a controller, which in turn directs (controls) the data/logic flow of the application. (Not the logic itself, the flow of the logic.)
That controller will then interact with the models (if necessary, sometimes the only action for a controller to perform is to immediately render another view, such as a redirect in a web application) and present the next view.
If data sent to the controller is needed in the next view, it would be the responsibility of the controller to include it in the next view.
I'm trying to use a html.dropDownList helper with a strongly typed view model with ajax. I can't the post the code because of the nature of the project.
Here basically what I'm doing...
loading a mvc view via a strongly type view model
clicking a button which does an ajax post to a controller method
using the TryUpdateModel to parse the view model
processing the request
rendering a parital view for the ajax request
According to the article listed below, the problem is that "ASP.NET MVC assumes that if you’re rendering a View in response to an HTTP POST, and you’re using the Html Helpers, then you are most likely to be 'redisplaying a form' that has failed validation."
http://blogs.msdn.com/b/simonince/archive/2010/05/05/asp-net-mvc-s-html-helpers-render-the-wrong-value.aspx
Instead of "redisplaying the same form value", I need the html.dropDownList to be set to the same value in the view model.
Does anyone know of any custom dropDownList helpers or have any ideas of how to achieve this?
Things I've already tried/considered
per the blog, manually removing the modelstate item...didn't work - didn't pick up the value in the view model - just defaulted to the first item in dropdown list
considered just writing a regular select list...but this is sloppy and cumbersome since I'm rending multiple select lists in a loop
writing my own custom dropDownList helper...wanted to avoid reinventing the wheel
Thanks in advance
Its not fully clear to me what your problem exactly is, but I've had a similar problem. I used the Html.DropDownListFor(, SelectListItem[]) helper. At postback it sets the value to the choosen one. Your postback view doesn't require to have all the fields of the original model.
#Html.DropDownListFor(model => model.SelectedValue, MyModels.DropDownSelectables());
Here I want the selected value as the model.SelectedValue variable and within my (seperate) model I made a array of selectlistitems. The rest is automagic.
Hope it helps, D
I am buiding a UI screen for editing the details of an Ecommerce Order. The model for my view (OrderModel) has everything I need (in properties that are also ViewModels), but the UI isn't designed to be able to edit all of it at once.
For example, one part of the UI is for customer data..another for order details, and another for tracking information, each having their own "Save" buttons.
I realize that I could use one giant form and use hidden form fields to populate the non-editable fields, making each "Save" button post all the data, but that smells bad.
I'd like to segment the editable chunks into smaller ViewModels that are posted and validated individually while retaining the strong typing but I'm unsure of how to achieve this in MVC3. Will I need partial views that are called from the primary view?
FYI, I'm using ASP.NET MVC 3 with Razor syntax and client side FluentValidation.
Partial Views are a good solution. You can pass different ViewModels to each partial view. But if only sections of the overall view are updated at a time I would not do a post back on the whole page. Instead I would use Ajax calls using JQuery/Javascript to update the individual information back to the controller. I would also look into something like Knockout.js to handle the data binding on the page.
I was going through the articles describing the MVC pattern. None of them were clear on explaining the role of Controller in MVC. Some says Controller can make changes to the view such as disabling a button or changing the text color whereas some says any changes to the view should be done inside view only. Can you please give me tips on the following question?
1) Can any change pertaining to the view be done inside the controller?
2) What not should be written inside a controller?
3) It is right to say "View should do all the changes by itself when a new recordset is generated by the model, as the view queries model directly, and controller is not involved in this transaction?"
4) I have heard this statement about MVC "In current version of windows application development. View is capable to handle the event(like button press) and the controller is called when needed.It is stupid to delegate the event listening to the controller now." Doesn't this sound more like a MVP?
Thanks. Hoping to get some help here.
In my opinion:
1) The controller changes the data provided to the view, so in a way, yes. The view should just manage the presentation of the data provided to it by the controller.
2) The controller should contain all code to handle any actions taken by the user. Depending on the size of your application, the controller can hand the action off to a business layer to do the work then gather view data once the business layer is complete and hand it back to the view. Or, if you don't have a business layer, it can do the work directly.
3) In true MVC, the view should not have access to the model directly. The controller should create view objects from the model and pass them to the view. In any case, the view should never do any real work other than presentation.
4) I don't know MVP so cannot answer this question.
1) Controller responsibility is primarily "execute an action, choose an appropriate view, provide some data to that view and return the view to a user".
2) As MVC tries to separate presentation logic and UI rendering, I believe, controller shouldn't attempt to perform any of view responsibilities: listening to UI events or pre-formatting of values dateString = data.ToString('YYYY-MM') - that's all should go to view.
3) in MVC view knows all about a model - model is rendered by view without any controller involvement (that's primary 'issue' fixed by MVP, where view should and model should unbound as much as possible). However it's not recommended for view to query model directly. Instead, all data changes should be reported to view by model using Observer pattern.
Consider the following -
schema from wikipedia article - dashed line from model to view indicates that fact. Just keep in mind that model is more viewmodel here and shouldn't really be a part of BL layer.
So here scenario could be the following:
User clicks "add item"
View sends request to the controller with the item data
Controller makes call to BL, which makes changes to the model (adds new item to the list).
Model fires "updated" event to the view (or "error" event, if there are some issues in underlying layers)
View updates UI according to changes reported.
4) The statement is perfectly true. In MVC you shouldn't do that. I assume, in MVP you shouldn't do that as well - I mean, listening to events from UI directly. That should be done either by forwarding event by view; or using a platform-independent view representation, like
inderface IMyGridView
{
event ItemEvent AddItemClick;
}
(which doesn't make sense for MVC, as view is pretty much independent from a controller and mostly all view actions are result in calls to controller).
In MVC pattern where does the response.redirect will come.Either in view and controller.
I'd also say in the controller. the view is only responsible for displaying the data and maybe doing a little data fetching. Although I'm restricting my views to just displaying and formatting.
So the controller has all the information when to redirect. So the result of a controller action is either a redirect or a view rendering. (Where presenting a download is considered as view rendering)
Must be in Controller.
Controller's name suggested that every control statement must come in the Controller.
View is responsible for the Design code only.
It will definitely come in controller.