Re: Why is CheckedMultiSelect so slow rendering 100 items?
If the number of options is more than 200, then rendering takes very long time.
I had this problem quite a while ago. The root cause was that because CheckedMultiSelect is heavily based on templates (each item is a template as well), with each added item parsing is kicked off (I think from within WidgetsInTemplateMixin) - and that is where the time is spent. I am not sure if one can get rid of this without removing the usage of templates.
You can use a dGrid with a checkbox column instead. Regarding checkbox column in dGrid, there is a sample or tutorial somewhere in the dGrid material.