Extend Multiple Choice with select all option functionality

Just wrote a blog article on extending your controls using the ControlExtender, you can create a form control inherited from it (see https://docs.kentico.com/k11/custom-development/developing-form-controls/inheriting-from-existing-form-controls ) and overwrite some of the features.

What you mean by "Select all checkboxes" will change what you do though. If you want all of them selected by default, then you should be able to extend it to set the option values to checked, as long as the values are created on the OnInit(e) and before you call base.OnInit(e) (since it's on the base.OnInit(e) that your ControlExtender will fire).

If you want to add some thing to allow users to select them all, then you may be better off cloning and adding more controls and such, as that's a little more than just extending what's there.

If you can provide more detail that would help!

I guess you are looking for for all check boxes selected by default i.e. on load? Here is an example. Essentialy you need to reproduce all checkbox values pipe separated. If the values for checkbox list comes from SQL query you need to create a custom macro that will output pipe separated values. If it comes from custom table you can do it using built-in macro syntax. Let say your custom table calle dropdown and the valued field is ItemId, you can put as default value this macro: {% string.Join("|", GlobalObjects.CustomTables["CustomTable.DropDown"].Items.ItemsAsFields.ItemID|(identity)GlobalAdministrator%}

The other way would be simply to add button and jquery to content before:

<div id=checkdiv>
 <input type="button" class="check" value="check all" />
    <script>
      $cmsj(function(){
        $cmsj('.check:button').click(function(){
              var checked = !$cmsj(this).data('checked');
              $cmsj('#checkdiv input:checkbox').prop('checked', checked);
              $cmsj(this).val(checked ? 'uncheck all' : 'check all' )
              $cmsj(this).data('checked', checked);
        });
       });
    </script>

and after </div>

@Trevor Fayas I am trying to implement control that allows user to select all the checkbox generated by multiple choice form control. Basically a select all checkbox will mark all other inputs as checked if selected. But I am not sure how should I go about it.

@Trevor Fayas Thanks a-lot, I would be able to do that now that you have made it clear.