We have implemented multiple RadComboBox controls in our solution that load items on-demand from web services.  We have marked all of them with EnableVirtualScrolling=true.  Everything is working in terms of the batch load of items when scrolling, however we are noticing strange scrolling behavior when reaching the end of the list of items.  When the vertical scrollbar reaches the last item (all items have been loaded), it jumps back up as if there is more area to scroll.  Thus, it is impossible to scroll to the bottom of the drop-down area.  We have tried setting both Height and MaxHeight properties, but the behavior is the same.  I noticed in the online demos for loadondemand virtual scrolling that the drop-downs indeed scroll to the bottom without issue. 

For some structural context, our combo box controls exist on a nested usercontrol form that is contained within a RadSplitter pane.  There is no custom CSS applied to the comobo boxes themselves.  Here is sample markup for one of our comboboxes:

<telerik:RadComboBox ID="SourceCombo" runat="server"         
      DropDownWidth="175px"           
      EmptyMessage="Select a source"           
      EnableLoadOnDemand="true"
      EnableVirtualScrolling="true"                     
      MaxHeight="200px"           
      OnClientSelectedIndexChanged="ClearSourceFilteredItems"
      ShowMoreResultsBox="true"          
      Width="175px">
 <WebServiceSettings Path="~/ES/LookupMethods.aspx" Method="GetSources" />
</telerik:RadComboBox>

Any suggestions on what we might be doing wrong?

FYI - we are using the latest SP build of the telerik controls, .NET 4.0, VS2010.

Austin

From your example, I was able to determine our issue.  In our web methods we were not setting the EndOfItems boolean property in our RadComboBoxData response.  I tested setting that property and it now stops scrolling when the last item is reached.  Makes sense, but must have missed that in the documentation/examples.

Thanks!

Austin