The MultiSelect widget is designed to show a popup element with suggestions. It is not designed to show calendar element, as the DatePicker is the widget designed to allow picking of dates. If you need to allow multiple selection of dates, one possible solution is to bind a MultiSelect widget to a predefined list of dates and allow the end user to choose one or more of them. Other way to handle your requirement is to use DatePicker widget, which on selection fills a list of dates. When a date is selected, you get the selected date put it in a list and clear the datepicker value. Check the DatePicker docs
for more information.
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