In the current version of RadControls there isn't a control that has that exact behavior but there are properties of the RadAutoCompleteBox control that could be used in order to achieve it. When a text is typed in the control its SearchText
property is populated with that text no matter if there is or there isn't a match in the DropDown portion of the control. And when a item is selected the SelectedItem
is populated. With those properties you could easily get the text when no selection is made (no match) or a selection was made.
I recorded a short video and attached a sample project of the previously described approach, hope this is helpful.