The contents of my MVCContrib grid come from the Model on a strongly typed View. When a post is made, the contents of the grid are not in the model object when it returns to the controller. I can see that this is because the grid renders as just a table with text in cells. Is there something I can do so that when the post occurs, the list data I sent down to the grid comes back in the post?
You can use TempData to persist this information server side. The information in TempData will persist for one request. I do not really like this option however.
Can you not repopulate your model from the db? If the user is not changing the information why do you need to post back all the same unchanged information? Just grab it again from where you got it before.
If you want to recreate the model as it was serialised into the grid, you will have to embed correctly named form elements within the grid ( or maybe outside the grid ) and within the same form as the one containing the button that is posting back to the action where you want your Model recreated.
While this is doable, you are essentially recreating __VIEWSTATE, and that defeats much of the joy of working with MVC ( read "it's an ugly hack and you should uninstall your IDE for even thinking it").
It is hard to point you in the right direction without having a better understanding of the scenario you are trying to solve. The usual workflow in these situations is
get the model
generate the page
record any changes to the model in a
form on the page
submit the changes to an action
get the model again
use TryUpdate to persist the changes
from the post into the model
If you are suffering performance issues ( you have proved you've got a perf problem right? You aren't optimising prematurely?), address them where they occur ( i.e. caching in your data access ), rather than bending MVC in ways it really shouldn't be.
Related
In an MVC4 project, I have a form that contains a partial view which is an index view of languages studied at school. It is a default type view template index, with Add, Delete, Edit links per row etc. When you Add or Edit, it opens an Add or Edit view for a Language. After e.g. adding a language, the updated partial view is returned.
My problem is that if the user opens the Language form, edits and captures on the main form will be lost. I can't just do an Ajax save before opening the Language form, as the main form may only be partially complete and fail validation. What I am thinking of doing though is using an AjaxPreserve action that takes a FormCollection, and stores it in session (o on disk, or anywhere) and therefore no model binding and server validation is performed.
I then have two problems: I will need to disable client validation before calling the AJAX action, and I will need to repopulate the main form using the FormCollection I saved earlier. I think there should surly be some jQuery voodoo to disable client validation, but I am completely stumped on repopulating the form.
ALTERNATE SOLUTION: Instead of using 'sub-forms', I can use editor templates, in pop-ip forms, where the FK IDs are not required, but that us only in certain cases, so my question still stands.
Could you use something like Knockout where you create javascript model and bind it to a grid/dialog edit/template view. I would transform the whole data to a JS model, bind it to a table/grid and then track all changes on the client side. When all is done, just serialize the whole model back to the server and update the data store.
If this is an acceptable scenario, it will save you a lot of trouble.
Familiarity with Knockout is required, but if you've used it before, you will be able to solve this in a very clean and efficient way.
This example on the Knockout website gives an idea of what I'm trying to suggest. Editing, deleting, adding is done on the client side until you send all of the data back to the server. You will need to track flags for each object to know if it's added, edited or deleted.
http://knockoutjs.com/examples/contactsEditor.html
Simple make the sub request for adding language using Ajax and repopulate the dropdown or what ever way you are accepting language on the main form on sucessfully save.
*This will save a lot of effort. *
Why don't you just use javascript?
E.g. You have main form, that stores some data. And when you need to add something specific like languages you open popup using partial view, allow user to fill form, but when user press submit you intercept action with js, save stuff to javascript array/object or whatever else and maybe store it in a hidden field of main form - for final submit
var newData = new Object();
newData.Field1 = $("#yourField1");
...
lanuageData.push(newData);
$("#languageContainer").val(JSON.stringify(languageData));
...
DataAnnotation validation works here as well like:
$.validator.unobtrusive.parse("your_partial_view_container");
When you need to edit some object that was already added to js array - open popup and fill it up with element of you js array. So basically you do all CRUD on client-side, saving changes only on final submit.
To make your code in a conrolller more clear you can use custom model binder which deserialize some string field from JSon to List or any other kind of object -> so it can be validated on server side.
Would saving your values to local storage be acceptable? What about using TempData?
First, I apologize if this is a dumb question, but I'm new to MVC and am trying to get up to speed as quickly as possible. I have spent hours searching for answers and even went and bought a book on MVC 4, but it still didn't answer my question.
I have a form I'd like a user to fill out to add a new product to the catalog. They choose the category, enter the name, a description, etc.. On the same page I'd like them to be able to add sizes or product options such as Small, Medium, Large, etc.. The problem is I'm not sure how to go about this.
I need to temporarily store the size options for example in some sort of collection until the user actually 'saves' the product, then I need to be able to read the collection. What I'm trying to avoid is to have the user add the basic product info, then save it, then select it, then choose to add options to it. I'm trying to just do it all on one form. Any help would be greatly appreciated!
There is nothing preventing you creating a view model with its own collections for the detail items and have those mapped to some sort of javascript control for selecting multiple items such as one that writes to an mvc hidden form control.
The controller handling the postback will simply create the master model from the postback data (the updated view model) and then create the child records. The whole thing could be achieved with ajax calling a controller action that returns a partial view of the updated ui.
Similar to this but have the list as a property of the master model
http://www.stevefenton.co.uk/Content/Blog/Date/201002/Blog/How-To-Handle-Multiple-Select-Lists-In-ASP-NET-MVC/
A little more advanced on how to manage your own bindings http://www.dotnetcurry.com/ShowArticle.aspx?ID=584
Sounds like u need to roll your sleeves up and get a control written in javascript that allows child items to be added client side whist serializing e.g. Into json when they save and saving it to an mvc hidden control ready for postback. Use json.net to hydrate these values into your pocos. http://erraticdev.blogspot.co.uk/2010/12/sending-complex-json-objects-to-aspnet.html
Ok, I looked a bit and couldn't find a good answer to this question.
Using ASP MVC3 I have a strongly typed ViewModel that has a list of custom objects retrieved from a repository. I render out using DropDownListFor as a dropdown selection. A value is selected and during the post I have a custom binder that rebinds my selected value to the custom object....Life is good...
I check my Model.IsValid and it is not valid for some reason. Uh, oh...I need to display the view again but I dont have the complete list of all options. Is there a way to repopulate all of the select option values in the custom model binder or some other method or do I have to hit my repository again?
Thanks.
You hit your repository again. Implement caching in your repository using a MemoryCache to save on DB hits and cache by key. This is the advantage of the repository pattern and the caller is unaware. Since by definition a repository is essentially an in memory representation this works out great.
Check out the implementation here it's similar to what I use and it works great.
http://stevescodingblog.co.uk/net4-caching-with-mvc/
Your currently selected item should remain selected since the HTML helpers read it from the posted data and reuse it.
I typically rebuild the list again and send back to the View. Often I'll use a factory method to inflate the viewmodel(s) with the necessary list(s). Hopefully, an invalid model will be a rare occurrence due to client-side validation in addition to the server side you're working with now.
While there are similar questions here, none gave a complete answer, so I am posting a new one.
I have a paged grid - jqgrid - which receives data from server by ajax, N rows (10, 20 and so on, depending on the user selection) each time. There is a boolean value in the grid row model, which is transformed into a checkbox in the displayed row.
When user checks the checkbox and then navigates to the next grid page, the state of the checkbox is obviously lost. What is the best approach to save it? Neither of the possibilities that I see fully satisfies me:
I can save the ids of the selected instances into a global javascript object on checkbox click. Thus when new dataset is obtained, I can iterate through all received instances looking for already selected ones. However this can mean a lot of javascript operations and possible slowdown for the final user, if there are a lot of selected instances.
I can store the selection on the server (session, database, whatever else). This way each time the model is generated, I will populate its boolean parameter with an adequate value. However, this can mean that when the user navigates away from my page without submitting the changes and then returns back, the record states will be restored. I am not sure whether this is good. Generally, I am strongly against storing anything on the server side before user submits the form.
So, what would you choose / offer?
I am using ASP.NET MVC 2.0, C# 4.0, if that matters.
Your question is essentially about preserving state in an ajax scenario that does not involve the evil webforms viewstate.
However, there is nothing wrong with viewstate when it is used to preserve state in the kind of scenarios you are working on (as opposed to providing a means to pretend a web page is a winform).
So, why not go for the best of both worlds and store the values in an encrypted hidden field, a sort of lean, mean, smart man's viewstate?
When you request the next page of data, pass back to the server the existing "viewstate" (if any) plus the new checked items, decrypt the viewstate on the server, see what is in there and if it is relevant to the next page, add the new list of checked items, encrypt that and send the new "viewstate" back to the user.
I haven't done this, so it is just an idea. However, it is logically feasible, and very practical. I say I haven't done this with a grid, but I have done it, with huge success, to design a wizard framework that works a dream.
My wizards preserve their state whilst the user is filling in the forms and only in the final step does anything get persisted (if at all, depending on what the app requires).
This framework is based on the wizard described in Steve Sanderson's book, but extended to work seamlessly with or without ajax. And with a very simple API for controllers derived from my wizard controller.
The code that makes this viewstate work is called from an OnActionExecuting method:
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
var serialized = Request.Form["wizardData"];
if (serialized != null) // Form was posted containing serialized data
{
WizardData = (TModel)new MvcSerializer().Deserialize(serialized);
}
}
And then in the ViewResult returned to the user:
<%= Html.Serialize("wizardData", Model)%>
In your case, as you are just paging data, you would need to serialize and encrypt the equivalent of the wizardData object and send this back with the JSON data to store somewhere in a hidden field.
This is a bit vague, as a wizard is a not a grid of paged data. But the principles (essentially, roll your own viewstate) do apply to both scenarios.
I have addressed this very situation by writing a list of the 'selected' checkboxes in a hidden div when the next page is selected. That way the client maintains the selection list, and no server interaction is required. In addition, when the user finally submits the page, I simply iterate over all the checkboxes in the visible page and the hidden div.
In my system, even in examples where users select hundreds of items, performance is not an issue.
In my web application framework (currently WebForms) I have a control that behaves like a classic propertygrid. It is initialized with an object ID (database key), then it reads metadata to determine the type of the object and the attributes of the object. It displays the attributes, string attributes as textboxes, bool attributes as checkboxes, enum attributes as dropdown lists. On page submit there is a method of the control ctrl.SaveData() that saved the changed attribute values back to the database.
The WebForm control tree and event model supports this approach quite nicely. Now I am asking myself if it is possible to achieve a similar solution for ASP.NET MVC. The main objective is to have a generic, reusable component that can be applied in a variety of situations with not much hassle. Additionally the solution must be flexible enough to put multiple instances of the component for multiple objects on a single page. Here the auto-generated WebForms HTML IDs also helped.
I am very curious about your ideas! Thanks a lot for answering!
You could achieve this effect using a custom ViewModel that contains enough metadata to identify the object being edited/saved. You would use this in conjunction with a partial view that renders the ViewModel. The main page would use the metadata in the ViewModel to either direct the post to a specific controller action to save that particular object or pass the metadata back to a common action (as hidden inputs, perhaps) in order that that action can choose the proper table in which to persist the data.
Personally, I would not take this approach. My feeling is that the more general you make a view/action, the more work it becomes to adapt it for different circumstances. I have done similar things for viewing sets of objects, but for a detail view or editing I like to work with more specific models and views.