The workaround is to set String.Empty for TextSearchPath before setting the new value for the DisplayMemberPath

1. RadAutoCompleteBox with an ObservableCollection set to its ItemsSource

2. The ObservableCollection is populated on the server side once the SearchText of the control changes.

3. The drop down part of the control closes itself even If there are filtered items.

If the control is placed inside ScrollViewer when the mouse is over the AutoCompelteBox control the mouse wheel is handled leading to no scrolling of the ScrollViewer.

As a workaround the Foreground property of the AutoCompleteBox can be set to Black.