It seems that in the Universal UI variant of the Telerik UI (2015.1.420.45, currently working on the WinRT Windows Phone 8.1 part), "SelectedItem" can not be used for binding. Apparently, the property "SelectedItem" does not have an accessible setter. When searching for the control, it seems that other variants (e.g., WPF) of the control do allow binding to the SelectedItem.
How to access the selected item via a binding from the ViewModel then, without writing some event-based code in the code behind file?
The tasks I'd need to do is:
1. Pre-set an item in the auto complete box (Two-Way binding) for the default value.
2. Get the selected item out of the auto complete box when the user is finished with the data entry form on the page.
My current workaround is to send the RadAutoCompleteBox as command parameter, to access its SelectedItem in the view model. But of course, it's not a good solution to work with the RadAutoCompleteBox control in the ViewModel. But switching to events and starting to use the code behind file isn't too much better. And for both workarounds, pre-selecting a value seems to be difficult.