As the original post was posted in the "UI for Windows 8 XAML Forum / AutoCompleteBox for XAML" section and the link
from your last post was for the WPF version of the AutoCompleteBox could you verify which platform you are using, Windows 8 or WPF?
If you are using the Windows 8 version the mentioned approach by Ves should work as expected. If you are using the WPF version of RadAutoCompleteBox note that the approach described earlier is not possible. In that case as you mentioned you could use a custom FilteringBehavior
and override its FindMatchingItems
method in order to implement a custom filtering by a different property of the objects.
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