How to Avoid Losing the State of Controls in ASP.NET MVC - asp.net-mvc

I'm working with ASP.NET MVC 2 and building a simple business app. Here are some of the details:
The app deals with work orders and
has a work order index view. The
view has a table listing the work
orders, and several controls (text
boxes, check boxes, and drop down
lists) to select the criteria for
which work orders to display.
I'm using viewmodels. The work order
index view has a viewmodel with
properties for each and every
control.
I've implemented paging similar to
what is being done in the answer to
this question:
How do I do pagination in ASP.NET MVC?
I'm using LINQ's Skip() and Take() as
demonstrated, and ActionLinks for the
navigation.
If I load the page and don't
manipulate any of the controls, I can
click on the page number ActionLinks
and move around just fine between
pages of work orders. However, if I
change something, my changes are lost
when I navigate to another page.
For example, if I'm on page 1 and
click an unchecked check box, and
then click on the link for page 2,
the second page of results will load
but the check box will revert to its
previous state.
I understand why this happens, but I'm wondering what is the best thing to do from a design standpoint.
Potential solutions I can think of:
Set all the control values as route
values in the ActionLinks. This
seems really nasty, and could result
in very long URLs or query strings. Actually, now that I think of it this wouldn't work without a way to capture the control values.
Since ActionLinks don't post
anything, replace them with buttons.
Again, this seems like a bad idea.
Change the ActionLinks to links that
fire off a jQuery script that does a
POST. I think this is the most
promising option so far. Do many
developers do it this way?
This seems like a common enough problem, but none of these options feel quite right. I wonder if I'm missing something.

Can't you just save the changes back to the database when the user toggles the checkboxes (using jQuery):
$("input[type=checkbox]").click(function() {
$.ajax({
type: "POST",
url: "/ControllerName/SaveInfo?id=" + {id},
success: function(){
alert("Data Saved: " + msg);
}
});
});

In the end, I wound up getting rid of the ActionLinks for the paging, and replaced them with regular anchor tags. The current page index is now stored in a hidden form value:
<input id="page" name="page" type="hidden" value="" />
<p>
<% for (var i = 1; i <= (int)Math.Ceiling(Model.RowsMatchingCriteria / (double)Model.PageSize); i++) { %>
<%--
If the page number link being rendered is the current page, don't add the href attribute.
That makes the link non-clickable.
--%>
<a class="pageLink" <%= i != Model.Page ? #"href=""javascript:void(0);""" : string.Empty %>><%: i %></a>
<% } %>
</p>
Then I added the following jQuery script, which sets the hidden page value and submits the form when a link is clicked:
$(document).ready(function () {
$('.pageLink:[href]').click(function () {
$('#page').val($(this).text()); // Set hidden field value to the text of the page link, which is the page number.
$('form:first').submit();
});
});
Problem solved.

Best bet is to effectively simulate viewstate by "logging" the changes to a hidden field when a user paginates. To do so:
1) Figure out what data you need to capture and a data format to do so in {ie -- an array of json objects}
2) Setup the link that handles the prev/next to fire off a method to collect the "changed" things and stuff them into objects and into a hidden field.
3) When posting the form, parse the hidden field, extract data and profit.

Related

In a Rails app, how can I make a link load in a div as opposed to refreshing the whole page?

I'm still a beginner at web development. It's not my profession. So go easy.
I started building a rails app today, and realized it would make my application so much better if I could get certain links to display in a separate div instead of a new page, or refreshing the entire page. I'm not quite sure how to search for this, and I keep chasing red herrings with google.
Basically, I have a list in a div on the left side of the page, and when one item from that list is clicked, it should appear in the right div. (Nothing else on the page need be changed)
That's really as simple as it is. Do I need to use Javascript for this? Can I get away with the rails js defaults, or should I be using JQuery?
Is there a way to do this without javascript? I really just need a push in the right direction here, I'm tired of not even knowing how to search for this, or what documentation I should be reading.
Like I said, go easy, and you should just go ahead and err to the side of caution, and assume I know nothing. Seriously. :)
Thanks in advance,
-Kevin
(By the way, I'm developing with Rails 3)
Create your views (along with controllers) to be shown inside the div for each item on the left menu. Lets say we have the following structure now:
Item1 (Clicking on it will fetch:
http://myapp.com/item1)
Item2 (Clicking on it will fetch:
http://myapp.com/item2)
and so on...
make sure you only render the html to be put inside your content div. Should not include <head> <body> etc. tags
In your main page you may have your markup like this >
<div id="leftMenu">
Item 1
Item 2
</div>
<div id="content">
Please click on an item on the left menu to load content here
</div>
Finally, add the following Javascript (you'll need jQuery; trust me it's a good decision).
$("#leftMenu a").click(function () {
$("#content").load($(this).attr("href")); //load html from the url and put it in the #content element
return false; //prevent the default href action
});
You will need JavaScript if you want to avoid reloading the page. You can use link_to for links in your lists, and you'll need to use :remote => true to make it send AJAX requests to the server. The server will need to respond appropriately and supply HTML for your div.
link_to documentation is here: http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to (and admittedly it isn't very useful for AJAX functionality).
The last post in this thread shows one possible solution you could use.

How do I let data in 1 column power the content of the 2nd column in Rails 3?

Say I have a list of users in the left column, generated by <%= current_user.clients %> and the second column is empty by default.
However, when the user clicks on one of the links, the second column becomes populated with the projects associated with that user - without the entire page being reloaded (i.e. using AJAX).
I would also like to continue the process, so when they click on a project from that user, the third column is populated with other things (e.g. the name of images, etc.).
How do I accomplish this in Rails?
I assume you are using Rails 3 and jQuery (I'm not well-versed in prototype). It's easy to switch jQuery for prototype in Rails 3: https://github.com/rails/jquery-ujs
For the link:
Something
Using JavaScript and jQuery, write a function that sucks in links of class first_column_link (please rename to something more reasonable, by the way):
$(function() {
$('.first_column_link').bind('click', function() {
$.getJSON('/clients/' + $(this).attr('data-client-id'), function(data) {
// Populate the second column using the response in data
});
});
});
This doesn't work on browsers that don't support or have otherwise disabled JavaScript. Gracefully degrading would likely be a good idea, but without more context, I can't advise you how to best do it.
<%= link_to_remote current_user.clients, go_to_controller_path %>
Proceed from there.
go_to_controller_path routes to an action which renders javascript to update the 2nd column (probably with a partial).

How to get the foreign key column data when it is used in a select box

I have this ruby on rails code
<%= builder.select(:serving_size_id, '') %>
I have not specified any options on purpose because I set the options in a different way when the page loads (using jQuery and Ajax).
The question: Is there any way I can get the value from the column "serving_size_id" but not change that line? I have a partial which I use it for new and edit and I think it would be sweet if I can do the setting of the selected index in JS.
Any ideas?
I'm not sure I completely understand your question, but if you want to set the value of the select field with JavaScript, you need to obtain the value in JavaScript at some point. I can think of two ways of doing this:
1) When you get the options via AJAX, have the server indicate which one is selected. This can be done by returning HTML <option> tags with selected="selected" set for one of them. To do this, your AJAX request is going to have to provide information about the object this select field is for (so the server can look up the object's current serving_size_id value).
2) When you render the field in your original partial, also render some JavaScript which sets the current value of the field, for example, underneath what you have above:
<%= javascript_tag "var ssid = '#{builder.object.serving_size_id}';" %>
Then, after the options are retrived via AJAX, the ssid variable is checked and the correct option is selected.
using jQuery in rails is easy but a little more difficult than prototype.
ex: "div id="serving_size" class="nice" rel="<%=h num%>">Stuff Goes Here.../div>"
in application.js do the following:
//application.js
$(document).ready(function(){
if($('#serving_size'){
$('#serving_size').live("mouseover",function(){
//we are hovering over specific div id serving size
if($('#serving_size').hasAttr('rel')){
alert($('#serving_size').attr('rel'); //your dynamic rel value, and fire function
}
}
}
if('.nice'){
$('.nice').live("mouseover",function(){
//we are now hovering over any item on page with class nice
if($(this).hasAttr('rel')){
//we are now using jQuery object ref and finding if that obj has attr rel
alert($(this).attr('rel')); // shows dynamic rel value
}
}
}
});
If you use the above code you should be able to do anything you want and fire any custom code from each of your set event callbacks.
The 'live' function in jQuery is great because it can be called on items that will eventually be on the page (eg. if you fill in something with ajax, jQuery will be prepared for that item being in the page)
I hope this help.

MVC DropDownList SelectedItem Value in ActionLink

I'm a bit confused and sorry if this question is repeated elsewhere, I did check and it didnt seem to be here yet.
Is there a way, (without use of JavaScript) to get the currently selected item of a DropDownList and say send it off to an ActionLink?
<%= Html.DropDownList("Elements") %>
<%=Html.ActionLink("Add Authorization Element", "AddElement", new {elementGuid = ??? }) %>
The bit I am looking for is something to replace:
???
Thanks,
Ric
Not without JavaScript, no. Of course, it's trivial with JavaScript.
If you want to do both, add JavaScript to the drop down, then put a submit button inside a noscript tag. Users without JavaScript will have to click the button. Users with JavaScript won't see it.

ASP.NET MVC: add to querystring on form submit

I'm building a grid in ASP.NET MVC and I have the following issue:
Above the grid i have a column selector which lets people customize the columns being shown. This is a form with a submit button so that people can add/remove multiple columns at once without going trough multiple postbacks.
Below the grid I have paging. This is paging trough actionlinks (a href's).
alt text http://thomasstock.net/mvcget.jpg
What happens when a user add/removes columns is that the form gets submitted to http://localhost:56156/?columnsToDisplay=EmployeeId and ofcourse the grid jumps back to page 1. I'd like to keep the grid on the page the user was currently on. So I need a way to include the current querystring parameters into the form's action attribute.
The other way around too: I need a way to do the same with actionlinks. But this is less necessary as I could always replace the a href's with buttons and put them in a form. But I'd rather not do that.
I'm looking for a solution without javascript! I can do it myself in javascript, but I'd like my grid to work perfectly on javascript-disabled browsers.
Any help is appreciated.
Edit:
Oh yeah, to make it a bit harder, I'm also looking for a solution without cookies/session variables. :-)
You need to add the line below into your column selector form
<input type="hidden" name="page" value="<%=Request.QueryString["page"]%>" />

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