CheckBoxList multiple selections: how to model bind back and get all selections? - templates

Question

This code:
Html.CheckBoxList(ViewData.TemplateInfo.HtmlFieldPrefix, myList)
Produces this mark-up:
<ul><li><input name="Header.h_dist_cd" type="checkbox" value="BD" />
<span>BD - Dist BD Name</span></li>
<li><input name="Header.h_dist_cd" type="checkbox" value="SS" />
<span>SS - Dist SS Name</span></li>
<li><input name="Header.h_dist_cd" type="checkbox" value="DS" />
<span>DS - Dist DS Name</span></li>
<li><input name="Header.h_dist_cd" type="checkbox" value="SW" />
<span>SW - Dist SW Name </span></li>
</ul>
You can check multiple selections. The return string parameter Header.h_dist_cd only contains the first value selected. What do I need to do to get the other checked values?
The post method parameter looks like this:
public ActionResult Edit(Header header)

Answer 1

I'm assuming that Html.CheckBoxList is your extension and that's markup that you generated.
Based on what you're showing, two things to check:
The model binder is going to look for an object named Header with string property h_dist_cd to bind to. Your action method looks like Header is the root view model and not a child object of your model.
I don't know how you are handling the case where the checkboxes are cleared. The normal trick is to render a hidden field with the same name.
Also a nit, but you want to use 'label for="..."' so they can click the text to check/uncheck and for accessibility.
I've found that using extensions for this problem is error prone. You might want to consider a child view model instead. It fits in better with the EditorFor template system of MVC2.
Here's an example from our system...
In the view model, embed a reusable child model...
[AtLeastOneRequired(ErrorMessage = "(required)")]
public MultiSelectModel Cofamilies { get; set; }
You can initialize it with a standard list of SelectListItem...
MyViewModel(...)
{
List<SelectListItem> initialSelections = ...from controller or domain layer...;
Cofamilies = new MultiSelectModel(initialSelections);
...
The MultiSelectModel child model. Note the setter override on Value...
public class MultiSelectModel : ICountable
{
public MultiSelectModel(IEnumerable<SelectListItem> items)
{
Items = new List<SelectListItem>(items);
_value = new List<string>(Items.Count);
}
public int Count { get { return Items.Count(x => x.Selected); } }
public List<SelectListItem> Items { get; private set; }
private void _Select()
{
for (int i = 0; i < Items.Count; i++)
Items[i].Selected = Value[i] != "false";
}
public List<SelectListItem> SelectedItems
{
get { return Items.Where(x => x.Selected).ToList(); }
}
private void _SetSelectedValues(IEnumerable<string> values)
{
foreach (var item in Items)
{
var tmp = item;
item.Selected = values.Any(x => x == tmp.Value);
}
}
public List<string> SelectedValues
{
get { return SelectedItems.Select(x => x.Value).ToList(); }
set { _SetSelectedValues(value); }
}
public List<string> Value
{
get { return _value; }
set { _value = value; _Select(); }
}
private List<string> _value;
}
Now you can place your editor template in Views/Shared/MultiSelectModel.ascx...
<%# Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<WebUI.Cofamilies.Models.Shared.MultiSelectModel>" %>
<div class="set">
<%=Html.LabelFor(model => model)%>
<ul>
<% for (int i = 0; i < Model.Items.Count; i++)
{
var item = Model.Items[i];
string name = ViewData.ModelMetadata.PropertyName + ".Value[" + i + "]";
string id = ViewData.ModelMetadata.PropertyName + "_Value[" + i + "]";
string selected = item.Selected ? "checked=\"checked\"" : "";
%>
<li>
<input type="checkbox" name="<%= name %>" id="<%= id %>" <%= selected %> value="true" />
<label for="<%= id %>"><%= item.Text %></label>
<input type="hidden" name="<%= name %>" value="false" />
</li>
<% } %>
</ul>
<%= Html.ValidationMessageFor(model => model) %>
Two advantages to this approach:
You don't have to treat the list of items separate from the selection value. You can put attributes on the single property (e.g., AtLeastOneRequired is a custom attribute in our system)
you separate model and view (editor template). We have a horizontal and a vertical layout of checkboxes for example. You could also render "multiple selection" as two listboxes with back and forth buttons, multi-select list box, etc.

Answer 2

I think what you need is how gather selected values from CheckBoxList that user selected and here is my solution for that:
1- Download Jquery.json.js and add it to your view as reference:
2- I've added a ".cssMyClass" to all checkboxlist items so I grab the values by their css class:
<script type="text/javascript" >
$(document).ready(function () {
$("#btnSubmit").click(sendValues);
});
function populateValues()
{
var data = new Array();
$('.myCssClas').each(function () {
if ($(this).attr('checked')) {
var x = $(this).attr("value");
data.push(x);
}
});
return data;
}
function sendValues() {
var data = populateValues();
$.ajax({
type: 'POST',
url: '#Url.Content("~/Home/Save")',
data: $.json.encode(data),
dataType: 'json',
contentType: 'application/json; charset=utf-8',
success: function () { alert("1"); }
});
}
</script>
3- As you can see I've added all selected values to an Array and I've passed it to "Save" action of "Home" controller by ajax 4- in Controller you can receive the values by adding an array as argument:
[HttpPost]
public ActionResult Save(int[] val)
{
I've searched too much but apparently this is the only solution. Please let me know if you find a better solution for it.

Answer 3

when you have multiple items with the same name you will get their values separated with coma