I am migrating from RadControls to Prometheus. I got a compiler error stating that property ExternalCallBackPage no longer exist. Searching the forum I saw that I have to use a webservice instead of ExternalCallBackPage.
However I want to create a multi column combobox using a header and item template. The webservice in the example given returns an array of RadComboBoxItemData objects. How can I use a webservice to populate a multicolumn combobox?