Unfortunately, this functionality is not directly supported by RadChart for Silverlight and I am sorry to say it but we do not deliver individual custom solutions in such cases.
You could actually achieve this to some degree, given you only need the line displayed. The line chart is actually an XY chart, so you can provide the DataPoints with corresponding values for XValue and YValue properties in the correct order and the line will be displayed along with the labels. However, you will not get categories along the vertical axis and the tooltips will not work correctly.
the Telerik team
Registration for Q1 2011 What’s New Webinar Week is now open. Mark your calendar for the week starting March 21st and book your seat
for a walk through all the exciting stuff we ship with the new release!