I have prepared a sample project demonstrating a possible approach to achieve the desired functionality.
Upon closing of the
drop-down list of the first RadComboBox an Ajax request to the server is made. Then on the server the checked items are retrieved using the CheckedItems
collection of the combobox. The second combobox is populated based on the currently checked items from the first combobox.
You could download the attached file and give it a try locally.
I hope this helps.
the Telerik team
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