HOw can i change content of ViewData on drop down list change using javascript in MVC View?
Short answer is: you can't.
Even if you could, nothing would happen Because you'd need to render your view with the new ViewData.
Javascript runs client side. That means, the user's computer.
ViewData is a server side collection. It is a data transfer object between your controller and view, which stays on your server.
You need to change the way you think. You can either make the change you want with javascript on client's comptuer when drop down changes, or you can post the value in drop down list and render the view with the new data, and send back to client.
If I'm not wrong you cannot change from client the server side object that is alive only during page rendering. You could change ViewData object of one page by putting there other data in controller.
Related
Is there a way to pre-populate a MultiSelectList with selected items?
Example:
I have a single View that has the following ListBoxFor that will cause the page to update what it's displaying by allowing filtering of Model.Companies.
#Html.ListBoxFor(m => m.SelectedCompanies, new MultiSelectList(Model.Companies, "IdString", "CompanyName")
What I'd like to have happen is after the update, the MultiSelectList will have the items that were selected before the page updated and refreshed. Does that mean I need to return SelectedCompanies with what was selected, or is there another way?
I am using the javascript library Chosen for usability of the ListBox on the client side, but I don't think that this affects what I'm trying to do.
Sometimes, JS libaries can interfere with your desired results. I can't speak for Chosen JS library, but inspect the markup and see how it renders. As long as it still has the listbox on the client (it must have some input element defined somewhere; my guess it hides it and updates the values as they are selected), then yes it should integrate fine.
However, when the controller posts back, you have to repopulate the Model.SelectedCompanies property with whatever values came back from the POST operation to the controller. The property should still have the selected companies if you return a View from the POST operation. If you are using a RedirectToAction instead, you'd have to store the selections in TempData.
I've understood that a viewmodel in MVC is supposed to reflect data on a single page rather than objects in the model. But should the viewmodel correspond to the data you want to show on that page or to the data you want back from that page? If we for example look at a login page then I just want username and password back in the post, but I might need more variables than that when displaying the login page (previous error messages etc).
Should the viewmodel then just contain username and password as parameters and the rest of the variables end up in viewbags. Or should the viewmodel contain all values I want to show even though I'm only interested in a few of them in the response.
What is best practice when using viewmodels?
All data that somehow interacts between the html and your server should be in a ViewModel.
This allows you to perform formatting and such outside your html and inside your ViewModel properties.
However, if your page contains a lot of controls or data, you may want to split it into multiple ViewModels (example one for the Get and one for the Post).
The post model may contain only data that you entered and needs to be validated.
I think it's best to put everything in the view-model. This keeps the code cleaner and makes discovery and maintenance easier as well. The view-model should be your primary mechanism here.
I would say only properties you need, in your case username and password. If you want to display error messages then that's what ModelState is for. You can always append any error messages to your ModelState:
ModelState.AddModelError("PropertyName", "Error Text")
Beyond that let's say you have a form that contains a list of categories that you need to pick one category from a drop down. In this case I usually attach that list to my model even though the only thing being submitted is the actual selected value. But this is a matter of preference, meaning I could also set a ViewBag to contain this SelectList of categories and then bind that to your DropDownList. I suppose it's better to place this in a model because ViewBag is dynamic and you will have to cast anything in the ViewBag into it's underlying type on your views.
Good morning,
I have a view that display's search results for customers. On top of the view i have a filter that has a few checkboxes. The user can select multiple checkbox items and press the filter results button. When the user presses the button it calls an action that filters the result. The page is also refreshed. My question now, how can i make the page remember what checkboxes are checked. Because when the results are returned the filter elements are reset.
Thanks in advance.
you can use TempData. TempData VS ViewBag VS ViewData
you used ViewData, After the redirect, the ViewBag & ViewData objects are no longer available
TempData is also a dictionary derived from TempDataDictionary class
and stored in short lives session and it is a string key and object
value. The difference is that the life cycle of the object. TempData
keep the information for the time of an HTTP Request. This mean only
from one page to another. This also work with a 302/303 redirection
because it’s in the same HTTP Request. Helps to maintain data when you
move from one controller to other controller or from one action to
other action. In other words when you redirect, “Tempdata” helps to
maintain data between those redirects. It internally uses session
variables. Temp data use during the current and subsequent request
only means it is use when you are sure that next request will be
redirecting to next view. It requires typecasting for complex data
type and check for null values to avoid error. generally used to store
only one time messages like error messages, validation messages.
TempData["CheckedList"] = YourCheckBoxListValues; //in your controller
in your View
#{
var tempchkboxList = TempData["CheckedList"] as yourStronglyTypeClass;
//or
var tempchkboxList = TempData["CheckedList"].ToString();
}
Depends on how long the input criteria should be remembered.
You could also save it in your session via Session["customerCriteria"] = yourCriteria, but it would be easier to give an example if you had provided some code.
You can keep your selected/checked checkbox details in session variable when you post the form (by clicking on the search button). In the HttpPost action,read the checkboxes which were checked and add that to a collection property of your viewmodel and send it back to the view. set the session variable values to null once you are done with it (after reading). in the view, use your viewmodel value to set the checked status of those checkboxes.
Another option is using ajax. When you click on search.Read your search criteria and make an ajax request to the action method. Return a partial view back and update only the div/table which shows the results of the search.
How do I can persist data in MVC Razor without using TempData between requests?
I see when we can use TempData from this, but don't want to TempData as it creates a state on the machine.
Thanks, Anish
EDIT: I want to persist the previous sort direction in a View page where a user is allowed to sort fields such as Name, Age etc.
FIX: I fixed it using ViewBag. Previous sort field/direction sent to View from Controller using ViewBag and then passed it back as query string in the next click.
Good FIX: I handled the everything in .js file such as checking and then in setting the previous sort field and previous sort dir in Controller.
This is what I finally did. I used ViewBag to send previous details to ViewPage and did the validation in a .js based on the current user action and passed it back to the controller in form-data.
Maintaining State in client page is something which is breaking the concept of HTTP which is stateless. Why do you want to maintain state ? If you are looking for some solution for Passing some data from your controller action to corresponding view, i would suggest you to go with a ViewModel where you fill the data for the dropdown and send that ViewModel object to the strongly typed view. You will have your data available there. Also you should grab data from your DataLayer ( from tables/ or Cache or etc..) in every request if you want some data.
You may pass a relevant id in the query string to get the corresponding data.
As RTigger mentioned, you may store some data in session. That will be available across all the pages till the life time of that session.
I haven't done a lot of ASP.NET MVC 3 recently, but I think the only real way you can persist data across requests is either with session state, cookies, or by posting data to the server every request.
ViewData, ViewBag, and TempData are all effectively killed at the end of each request, whereas session state, cookies, and post data is made available at the beginning of every request based on information from the client browser.
What particular scenario are you trying to persist data for?
You could pass those values as query string parameters when redirecting.
You can set parameters to hidden input fields if you post the form. But if you gonna call action by HTTPGET then you can pass values by using QueryString parameters.
I have the following scenario:
I have an edit page, which can be called from different pages. These pages could be the detail view for the current entity, or the list view for the entities (with or without a search in the route).
HOW do I cleanly redirect to the original calling page using the MVC framework? Of course I could simply pass the HttpContext.Request.Url value by holding it in my TempData, but that sort of smells, in my eyes (or, err, nose). It's on a lower level than the rest of the code.
Is there a way to get the routevalues for the previous page in a controller context? If I have that, I could store that temporarily and pass that to the redirect.
Do not use TempData when not redirecting. One AJAX request from your edit page, and the TempData will go away.
Tomas is right that a hidden element or query string parameter is the way to go. But make sure you sanitize the value submitted. You don't want to redirect any old site on the web; you need to ensure that the page to which you redirect is part of your sites.
you can always have a hidden form element telling the controller where to redirect when posting a form. when using a get request, you could use a querystring in a similar way. it might not be the most beautiful solution, but it's quite a lot safer than trusting httpreferrer or other headers that could easily be changed (or ommitted) by the browser.