I have cascading dropdowns in my MVC partial view. DD1 drives the values in DD2. When I select DD1 I want DD2 to be populated with, based on a DB table, the correct values based on DD1's value.
My thought was to make DD2 a partial view and nest in my form. Then, with ajax, I can tell the partial view to refresh and pass it the value of DD1.
The problem is, when I submit the whole view (with both DD1 and DD2 and a bucnh of other stuff, how do I get the value that is in DD2?
I'm trying to solve this problem using MVC, rather than triggering a javascript function on change of DD1 to make a JSON call to get the options and then using javascript to modify DD2 to the correct values.
How should I do this?
How big are your value sets for each drop down?
I was attempting to do this same thing a few years ago. DD1 was United States and Canada, and DD2 was the associated States and Provinces. If your data set is relatively small, you're better off just putting all the select list markup for both cases in the page, and then swapping it out with javascript (jQuery). You'll be saving yourself the request round trip, regardless of whether you go ajax or a full page refresh.
If the data set is large and it doesn't make sense to put all values in the markup, and you want to use MVC views instead of modifying the DOM with an ajax call, then just refresh the entire page. If you want to go ajax, then just modify the DOM with jQuery; you don't need a partial view to accomplish this.
You are going to have to use javascript unless you want to do an entire page postback. For this type of thing, javascript/ajax is the way to go. I personally had a hard time when I switched to MVC having to accept that all this business logic was happening outside of the MVC model. But in the end, it's whatever makes the website work best (user doesn't see your code and know how pretty it is).
Anyway, partials won't work either unless you post the whole page since without using javascript, the partial is rendered as part of that page/form.
I would just add a onchange event to the first dropdown that triggers a json call to a method in the same controller...something like
...jquery...
$("#mydropdown").change(function() {
$.post("/Controller/DropdownChangedJSON", { firstdropdownvalue: $("#mydropdown").val() }, function(data) {
$("#seconddropdown").empty();
// loop through "data" to populate dropdown
}); //post
}); //mydropdown_change()
and in your controller:
public JsonResult DropdownChangedJSON(string firstdropdownvalue) {
//get results
List<datamodel> myarray = //something
return new JsonResult { Data = new { success = true, rows = myarray } };
}
hope this helps
Related
Our users asked to have the Kendo Tree show up in the MVC web app in a panel on the left hand side of the page. They want that left hand panel to be present on every screen.
Currently I have a section of my _Layout.cshtml page that renders the Kendo Tree:
<div>
#{Html.RenderAction("GetTree", "Tree");}
</div>
Inside that Action I make a database call to get the contents of the tree and bind the model to the view as follows:
#model IEnumerable<TreeViewItemModel>
But obviously with this pattern every page I go to the _Layout gets called and the tree data is fetched from the database again. This is not very efficient.
What is a better way so that I only make a single database call?
I'm going to assume that the content of the tree is the same for every page and every user.
In that case, you can cache the retrieved database data so that you don't have to retrieve it on every page render. There are lots of ways to cache it: the simplest is probably to use ASP.NET's own caching, which is described in detail (with walkthroughs) here.
You probably will still have to render it on every page (unless you want to get into partial page caching, and I'm not sure how that works in MVC) but you definitely can avoid the repeated database hit.
ETA: You can create a wrapper or helper class that retrieves the necessary tree data by company. The relevant method would look a bit like this:
public IEnumerable<TreeViewItemModel> GetCachedTreeDataByCompany(int companyId)
{
var data = Cache["TreeData"] as IEnumerable<TreeViewItemModel>;
if(data == null)
{
data = GetTreeData(); // whatever you need to do to get the data
Cache.Insert("TreeData", data);
}
return data.Where(tvim => tvim.CompanyId == companyId).ToArray();
}
I have a fairly simple site with a Search partial view and a Listing partial view. They're rolled up using multiple models into the Index view.
Everything is fine. Except when I click the grid column headers to sort or attempt to page to the next listing of data, the grid comes back empty. If I re-submit the same search criteria, then the grid repopulates with all applicable data sorted or paged properly.
I've tracked this behavior down to the fact that the WebGrid sets up it's paging and sorting mechanisms as a GET instead of a POST. So obviously all my model data is left off the submission.
Isn't there a way to get the WebGrid to POST so the data tags along? Seems quite counterproductive for the WebGrid as a class to not include the data one wants to page or sort.
Old question, but just to add a reference:
I preferred the solution suggested at this link
which solves the problem using JQuery:
var links = $('a[href*=page], a[href*=sort]'), form = $('form');
links.click(function () {
form.attr("action", this.href);
$(this).attr("href","javascript:");
form.submit();
});
This may not be the most elegant solution, but it works:
Add the model to your Session in the view:
Session.Add( "Model", Model );
Then, in the Index GET Action in your controller (or whatever the GET Action is), just check for the value and call the POST Action:
if ( Session[ "Model" ] != null )
this.Index( Session[ "Model" ] as MyModel );
Cleanup your Session accordingly.
Further to the JQuery answer above (which brought me success, thanks!) don't forget to undelegate the the webgrid's own magic methods that it adds behind the scenes. Otherwise you may end up with another ajax GET occurring at the same time as your POST.
Before binding to the 'page' and 'sort' links do this:-
$("#MyWebGridID").undelegate();
I'm making the transition from webforms to MVC (I know, 3 years late) and I "get it" for the most part, but there's a few things I'd like advice and clarification on:
First off, what happens if you want to dynamically add inputs to a view? for example, in an old webform for generating invoices I had a button with a server-side click event handler that added an extra 5 invoice item rows. The stateful nature of webforms meant the server handled the POST event "safely" without altering the rest of the page.
In MVC I can't think how I'd do this without using client-side scripting (not a showstopper, but I would like to support clients that don't have scripting enabled).
The second problem relates to the invoices example. If my Model has a List, how should I be generating inputs for it?
I know data binding is a possible solution, but I dint like surrendering control.
Finally, back to the "stateful pages" concept - say I've got a Dashboard page that has a calendar on it (I wrote my own calendar Control class, the control itself is stateless, but can use the webform viewstate to store paging information) - how could a user page through the calendar months? Obviously POST is inappropriate, so it would have to be with GET with a querystring parameter - how can I do this in MVC? (don't say AJAX).
Thanks!
In MVC you design your actions to accommodate your needs. For example, if you wanted to be able to add 5 rows to an invoice NOT using client-side scripting, you'd probably have your GET action for the invoice generation take a nullable int parameter for the number of rows. Store the current number of rows in the view model for the page and generate a link on the page to your GET action that has the parameter value set to 5 more than the current value. The user clicks the link and the GET view generates the page with the requested number of rows.
Controller
[HttpGet]
public ActionResult Invoice( int? rows )
{
rows = rows ?? 5; // probably you'd pull the default from a configuration
...
viewModel.CurrentRows = rows;
return View( viewModel );
}
View
#Html.ActionLink( "Add 5 Lines", "invoice", new { rows = Model.CurrentRows + 5 }, new { #class = "add-rows" } )
You would probably also add some script to the page that intercepts the click handler and does the same thing via the script that your action would do so that in the general case the user doesn't have to do a round trip to the server.
<script type="text/javascript">
$(function() {
$('.add-rows').click( function() {
...add additional inputs to the invoice...
return false; // abort the request
});
});
</script>
Likewise for your calendar. The general idea is you put enough information in your view model to generate all the actions that you want to perform from your view. Construct the links or forms (yes you can have multiple forms!) in your view to do the action. Use parameters to communicate to the controller/action what needs to be done. In the rare case where you need to retain state between actions, say when performing a wizard that takes multiple actions, you can store the information in the session or use TempData (which uses the session).
For things like a calendar you'd need the current date and the current view type (month/day/year). From that you can construct an action that takes you to the next month/day/year. For a paged list you need the current page, the current sort column and direction, the number of items per page, and the number of pages. Using this information you can construct your paging links that call back to actions expecting those parameters which simply do the right thing for the parameters with which they are called.
Lastly, don't fear AJAX, embrace it. It's not always appropriate (you can't upload files with it, for example), but your users will appreciate an AJAX-enabled interface.
In MVC you can store application state in various ways. In your controller you have direct access to the Session object and you can also store state to the database.
your view can contain basic control flow logic, so, if your model has a list you can iterate over it in the view and, for example, render an input control for each item in the list. you could also set a variable in a model to be the maximum number of rows on the viewpage and then render a row in a table for the number specified by the model.
paging is basically the same thing. you can create a partial view (user control in the webform world) that shows page numbers as links, where each link calls an action that fetches the data for that page of results.
i'm not sure what your beef is with ajax or javascript
I am new to ASP.NET MVC, particularly ajax operations. I have a form with a jquery dialog for adding items to a drop-down list. This posts to the controller action.
If nothing (ie void method) is returned from the Controller Action the page returns having updated the database, but obviously there no chnage to the form. What would be the best practice in updating the drop down list with the added id/value and selecting the item.
I think my options are:
1) Construct and return the html manually that makes up the new <select> tag
[this would be easy enough and work, but seems like I am missing something]
2) Use some kind of "helper" to construct the new html
[This seems to make sense]
3) Only return the id/value and add this to the list and select the item
[This seems like an overkill considering the item needs to be placed in the correct order etc]
4) Use some kind of Partial View
[Does this mean creating additional forms within ascx controls? not sure how this would effect submitting the main form its on? Also unless this is reusable by passing in parameters(not sure how thats done) maybe 2 is the option?]
UPDATE:
Having looked around a bit, it seems that generating html withing the controller is not a good idea. I have seen other posts that render partialviews to strings which I guess is what I need and separates concerns (since the html bits are in the ascx). Any comments on whether that is good practice.
look at the ContentResult you can specify the mime type of what you return (text/html)
You could alternatively make a control that take a IEnumerable of whatever you put in the selectlist, and build it using the view engine. That way you keep the formatting of the html (in this case a list of options) into a view, and not in your code.
<%# Control Language="C#"Inherits="System.Web.Mvc.ViewUserControl<IEnumerable<Article>>"%>
<%foreach (var article in Model){%>
<option><%:article.Title %></option>
<%} %>
I think I would go for that second one
From what I understood, the jQuery dialog contains a form that, when submitted, will post to an action which updates the database with some information. You want to get the newly added database information and update the same form that was used to trigger the database update.
If that is the case, then I think the best clean and logical option is to return JSON serialization of the items to be put in the drop down right after you update the database. Then, using jQuery, you would clear the drop down and append option tags into it.
You can also write a new, seperate action that returns the JSON serialization of the database objects you need. You would have jQuery call another post to this action as a callback to your first ajax post (the one used to update the database).
Here is a quick snippet
public ActionResult UpdateDatabase(string something)
{
/// update the database
IEnumerable<Items> items = getItemsFromDatabase(); // or w/e
var vals = items.Select(x=> new { value = x.ID, text = x.Name }); // something similar
return Json(vals);
}
Personally, I would write a separate function that returns JSON. This ensure separation of concerns, and gives me a function I can use in many different places.
Returning a JsonResult with all the items is the most versatile and least-bandwidth intensive solution as long as you are happy to iterate through the list in jQuery and update your drop-down list.
Using a partial view is nice for HTML that you can .load(...) directly into your select, but less versatile.
I would go with the JsonResult.
In your Controller:
public JsonResult UpdateItem(string sItem)
{
// 1. Insert new item into database if not exist...
// {update code here}
// 2. retrieve items from database:
IEnumerable<Item> Items = GetItems();
// 3. return enumerable list in JSON format:
return new JsonResult{ Data = new {Items = Items, Result = "OK" }};
}
On client-side:
Iterate through Items array and add the items to your list.
I have two forms on one page: a results form and a search form. The search form uses a partial view because it is displayed on several different pages. I want to be able to persist the data in the search form regardles of which button on which form the user clicks. The problem is that when the user clicks on a link or button from the results form, only the form values from the results form are posted, the values from the search form are not included. How can I maintain the values in the search form even when it is not the form that is submitted? I do not want to use any type of session state to maintain the form and I dont want to write the search values in hidden fields in the results form. I just want to be able to post them with the form values of the results form so that the users search criteria can be maintained accross any page that displays the search partial view. What am I missing?
The first thought that occured to me is to remove the form wrapping the search control and just let it be rendered into the form with the results data. I worry here about naming conflicts. What happens when the search from has a control with the same name as the results form, wouldn't this cause a naming conflict? I suppose that this could just be managed manually to ensure that there are unique names whenever rendering partial views into other views, perhaps even going so far as to prefix values with the partial view name, but that reminds me of the ugliness that is INamingContainer in web forms - plus makes for cumbersome field names in your model.
Is there some sort of elegant solution that will allow a form to persist state that I am missing? Thanks!
Normally, I persist the search criteria on the server side when the search is performed. If the user changes the search criteria after performing the search, then posts the form any changes are, of course, lost but that's arguably correct behavior since the search wasn't invoked. This is true whether the search is performed from a full post or via ajax. Handling it this way keeps the actions cleaner, I think as you don't need to handle the search data in the other actions.
If you absolutely need to have the search parameters included, you could consider having the second form post via javascript, pick up the search field values dynamically and add them to the second form (as hidden fields) prior to posting the second form. You wouldn't have to maintain the values in two places in synchronization, but you would have to copy them to the second form before posting.
At the moment i got it like this:
Forms which has search box, posts query (and additional data if needed) to search controller which then renders search view. Search view is made from search box and search results partial views. During this - search box form is reconstructed by posted data.
If i need search results form to perform another search request (for example, with specified page index), it goes through ajax, which posts search box form + page index from search results form. Take a look here for ideas (update that JS method with targetId parameter for updating specified div/form and post additional data if needed here like this:
form.serialize()+"&pageIndex=5"
In short: if you need to maintain state of form + update another in one page - consider using partial updates, otherwise you will end up inventing ViewState 2.0.
One caveat with this way - it's tricky to make search box contain something what is related with search results (i.e. - total count of found items). Before i managed to handle this, our designer did that - i just need to add div with appropriate class name ("sbsubst" or something) and it looks that it's inside search box. :)
When you have few forms at your page each form sends only its own data. In WebForms you had only one form (at least server-side) and each control was included into this form. In ASP.NET MVC you can use the same scenario and I'm afraid you will have to if you want to have the described behavior. Don't forget - partial forms don't have to be real forms. Moreover, RenderPartial is mostly used for "control-like" layout creation.
As for the second part of your question I would suggest naming your text boxes in search form with some normal prefix like "search" or something like that. For instance, if you have text box "text" and "language" in the form, you will have "searchText" and "searchLanguage". These names are quite unique and you will have normal names in your parameters.
I am not suggesting you populating the hidden values in your results form on POST event since you said it's not an option for you but still it may be the only way if you want to have two forms.
I think the best approach will be storing the text from search input when it changes in the query part of your second form action url. For example (not tested):
$('input#yourSearchInput').change(function()
{
var searchText = $(this).val();
// or? var searchText = encodeURIComponent($(this).val());
var secondForm = $('form#secondFormId');
var action = secondForm.attr('action');
var queryStart = action.lastIndexOf('?search=');
if(queryStart > -1) {
action = action.substring(1, queryStart);
}
action = action + "?search=" + searchText;
secondForm.attr('action', action);
});
In Controller (or custom filter):
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
var search = Request.QueryString["search"];
if(!String.IsNullOrEmpty(search)) {
ViewData["SearchFromPOST"] = search;
}
base.OnActionExecuting(filterContext);
}
In your Search Control:
<%= TextBox("yourSearchInputId", ViewData["SearchFromPOST"]) %>