RadMultiSelect is available as of R1 2020 and it is a server-side WebForms wrapper over the MultiSelect for Kendo UI for jQuery widget.
It operates on the client, displays a list of options and allows multiple selections from this list. It provides full control over the rendering of items, selected values, and popup headers.
Renders and operates on the client-side
Built-in accessibility, WAI-ARIA, keyboard and RTL support
Single and Multiple Tag Options, giving the ability to customize the way the selected values are displayed
Client templates for all components
Built-in grouping of the data
Client or server filtering
Integration with both client-side and server-side data sources