Kendo UI validator is intended to provide validation for input elements and works on the basis of HTML5 validation attributes. That said, it is not possible to make a ListView widget required - the <div> element is not an input and does not have required attribute.
As a workaround I can suggest using a custom rule
bound to a hidden input. This will let you to write your own validation function which will check whether there is a selected item
. You would also have to customize the tooltip position
and display it near the widget.
the Telerik team
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