Hi Jonathan,
In order to use the auto generated items, you have to work with the collection that is already set to the ChartLegend.ItemSource (instead of setting a new collection to it). Basically you need to change your last line with this:
However when I tested this I noticed that if the code is executed in the RadChart.DataBound event handler, initially the chart legend items are not reversed. You can fix that by moving the code in the RadChart.LayoutUpdated event handler. The RadChart.DataBinding event is a appropriate moment to attach to the LayoutUpdated event. Here is an example:
Greetings,
Petar Kirov
the Telerik team