kendoDropDownFilter directive doesn't work on grouped data

[Noah]

If the dropdown items are using the grouping functionality then the built in filtering directive doesn't work. at least for multiselect.  I don't know about all dropdowns.

[Martin]

Hi Noah,

Thank you for the provided feedback.

Indeed the built-in filter directive does not work with group data by default, due to the changed architecture of the collection when grouping is applied. We will update the documentation accordingly in order to avoid any potential misunderstanding in the future.

As another option of achieving this behavior, the developer can handle the filterChange event manually as the following article demonstrate:

https://stackblitz.com/edit/angular-ftrajg?file=app/app.component.ts

I hope this helps.

Regards,
Martin
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