In order to achieve a similar to the desired behavior you could use the TextSearchMode property of RadComboBox and set is to Contains and enable the filtering functionality using the IsFilteringEnabled property:
You might also want to consider using our RadAutoCompleteBox
. It provides auto-completion functionality with Contains mode our of the box. You could also check the sample that demonstrates how to add a button to RadAutoCompleteBox to make the control more similar to RadComboBox in appearance:
Hope this helps.
Telerik by Progress
Do you need help with upgrading your WPF project? Try the Telerik API Analyzer
and share your thoughts!