My view page contains a search-by-example form with the following checkbox code:
<td>
<label for="HasProcessErrors">Has Errors:</label>
<%= Html.CheckBox("HasProcessErrors", crit.HasProcessErrors) %>
</td>
The crit object HasProcessErrors property is a boolean whose initial value is false. When I view the source of my rendered page, I see that the helper has generated the following HTML:
<td>
<label for="HasProcessErrors">Has Errors:</label>
<input id="HasProcessErrors" name="HasProcessErrors" type="checkbox" value="true" /><input name="HasProcessErrors" type="hidden" value="false" />
</td>
Have I used the CheckBox helper incorrectly here, or is something odd going on? It seems like it should generate an input of type checkbox with checked = "".
Thanks for any ideas.
Yes this is correct.
The semantics of a checkbox are a little bit different from what you may think; instead of posting a value indicating its checked/unchecked state, a checked checkbox posts whatever is in its ‘value’ attribute, and an unchecked checkbox posts nothing.
As there is also a hidden field with the same name, if you debug your form submit, you will find a checked checkbox has the value 'true,false' whilst an unchecked box has the value 'false'
You can determine if a checkbox is checked by testing if it contains 'true'.
public ActionResult(FormCollection form)
{
bool checked = form["checkbox_id"].ToString().Contains('true');
}
Related
Is there any way to set check_box_tag unchecked value to any other value than nil? Something like:
check_box_tag :active, ['true', 'false'], ...
In the HTML specifications unchecked checkboxes are not included when sending the form. So there is no "unchecked value" for a checkbox.
There is a workaround though - you include a hidden input with the same name attribute as the checkbox:
<input type="hidden" name="active" value="deader then dead">
<input type="checkbox" name="active">
Since key/value pairs have to be sent in the same order they appear in the form the checkbox will override the hidden input if it is checked.
The higher level Rails checkbox helper has this workaround built in.
I'm using the <li><%= Html.CheckBox("IsPublic", false) %></li> checkbox. It creates <input id="IsPublic" name="IsPublic" type="checkbox" value=""><input name="IsPublic" type="hidden" value="false">.
I can't get it to return a true value. When checked, and submitted to a FromCollection, it's value is ",false" which still gets interpreted as false.
Without the checkbox I can have the Controller method be something like public JsonResult CreateThing(MyThing thing) and it correctly places all the fields. Now with the checkbox I'll have to manually set every field from the FormCollection unless I can get the checkbox to be automatically interpreted correctly.
I appreciate assistance.
I have a search form which I return to after searching, to be able to refine the search. I just added a checkbox to that form.
In the view:
<%= f.input :available_tomorrow, as: :boolean, label: false,
inline_label: t('public.search.form.available_tomorrow.label'),
input_html: { name: :available_tomorrow, value: params[:available_tomorrow],
id: :available_tomorrow } %>
In the model:
attr_reader :available_tomorrow
HTLM produced:
<div class="form-group boolean optional search_available_tomorrow">
<input name="available_tomorrow" type="hidden" value="0">
<label class="checkbox">
<input class="boolean optional" id="available_tomorrow" name="available_tomorrow" type="checkbox" value="1">
Available tomorrow
</label>
</div>
When I check the box, all search parameters appear fine in the url querystring but that one:
&available_tomorrow=0&available_tomorrow=1
Looks like the value property of both field is sent, and neither changes. If I uncheck the box, I only get &available_tomorrow=0 in the querystring. The second part is only added if the checkbox is checked.
Everything works as intended (the search does return the right results depending on the checkbox state, the checkbox is in the right state when the search form is updated). But that querystring is ugly with both available_tomorrow parameters, looks like the first one should never appear. Ideas?
This is normal behavior for a form with a checkbox when you POST the form: If the checkbox is not checked, only the hidden field with value 0 is sent with the formdata. If the checkbox is checked, the input with the value 1 is also sent.
The hidden field for the checkbox is always sent, this is because otherwise no value for the checkbox would be sent.
Long story short: don't mind the querystring in your search url, nobody will ever look at them. :)
Basically I have a set of checkboxes that are dynamically created from view data like so:
<input type="checkbox" name="Calendars" value="<%= c.ID %>" /><%= c.Name %>
The value being the Calendar Id.
I can get what checkbox has been brought back using the FormsCollection its messy but it works!
(There also seems to be a bug with the checkbox helper that renders a hidden field next to the checkbox which means true is actually returned as "true,false"! I can work around this so its not an issue just thought Id mention it)
The problem comes when trying to hook the checkboxes up on an edit page!
I have a schedule class which can have multiple calendars and I want to show which calendars a schedule has by checking them on the edit!
My view is strongly typed but MVC magic can't map this!
Any ideas on whats the best way to do this??
I had tried passing the calendar ids in ViewData and do some inline code to check the appropriate checkbox but this is getting messy!
Thanks!!
UPDATE:
Done this
s.ID == c.ID).Select(s => s).Count() > 0) ? "checked=checked" : "" %>
You need to add "checked" tag manually to every check box:
<input type="checkbox" name="Calendars" value="<%= c.ID %>" checked="checked" /><%= c.Name %>
You dont need <input type="checkbox" - use Html.Checkbox(). It renders a hidden field next to the checkbox - but it is not a bug. From ASP.NET MVC source, InputExtensions.cs, line 201:
// Render an additional <input type="hidden".../> for checkboxes. This
// addresses scenarios where unchecked checkboxes are not sent in the request.
// Sending a hidden input makes it possible to know that the checkbox was present
// on the page when the request was submitted.
Use this:
<%= Html.CheckBox("Calendars", c.ID) %>
The code
<%=Html.CheckBox("SendEmail") %>
evaluates to two HTML elements when it's rendered
<input id="SendEmail" name="SendEmail" type="checkbox" value="true" />
<input name="SendEmail" type="hidden" value="false" />
Is this by a bug? Or by design? If it's by design, why?
I was having some trouble this morning with retrieving selected values from a checkbox group in my MVC app. I sent this out to my team and thought I'd share it with everyone else.
When posting back values for checkboxes, the standard behaviour of all browsers is to completely leave out un-checked checkboxes from the post back. So if you have a checkbox that isn’t checked then nothing shows up for this in Request.Form. This is a fairly well-known phenomenon that most developers account for.
In ASP.Net MVC when you use Html.Checkbox, it attempts to get around this and ensure that you have a value posted back (in this case ‘false’) for un-checked checkboxes. This is done by adding a hidden field containing the value ‘false’.
Eg.
<%= Html.CheckBox("Sites", s.Selected, new { value = s.Value })%>
Produces the HTML
<input id="Sites" name="Sites" type="checkbox" value="1" /><input name="Sites" type="hidden" value="false" />
This is all good and well, until you attempt to use checkbox groups. That is more than one checkbox with the same name where the values are sent back in a single comma separated string.
MVC can split this string up for you automatically if you define the value as an array (string[] Sites).
Here’s the view code:
<% foreach(var s in Model) { %>
<li><%= Html.CheckBox("Sites", s.Selected, new { value = s.Value })%>
<label><%= s.Name %></label>
</li>
<% } %>
The appropriate controller action:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(int Id, string Name, string SubmissionUrl, string[] Sites)
Unfortunately, because the Html.Checkbox produces this hidden field value as well, the resulting array contains not only values for the selected checkboxes but also ‘false’ for every un-checked checkbox. You get an array that looks something like this:
[0] 'false'
[1] 'false'
[2] '110'
[3] '50'
[4] 'false'
Where 'false' is for checkboxes that are not selected, and integers are the values for the checkboxes that are selected.
This can throw your code out quite a bit if you have only integers for the values of your checkboxes and want to define the result as an array of integers, like so:
public ActionResult Edit(int Id, string Name, string SubmissionUrl, int[] Sites)
Which results in an exception being thrown because it can’t convert the string value ‘false’ to an integer.
The solution is very simple, just avoid Html.Checkbox and manually create the checkboxes in your view code like this:
<% foreach(var s in Model) { %>
<li><input type="checkbox" name="Sites" value="<%=s.Value%>" <% if (s.Selected) { %>checked="checked"<% } %> />
<label><%= s.Name %></label>
</li>
<% } %>
Hope this helps someone else!
When all else fails, read the source code. :) this is from HtmlHelper.cs:
// Render an additional <input type="hidden".../> for checkboxes. This
// addresses scenarios where unchecked checkboxes are not sent in the request.
// Sending a hidden input makes it possible to know that the checkbox was present
// on the page when the request was submitted.
I'm not exactly sure how useful that is, but at least you know the intention.
I think I found something on the web that is directly related to my question.