This type of scenario is a bit tricky and can't be done in XAML alone. Because you can have up to two separate bars for each chart category, this makes Category2 dynamic - you can have a single value (Grade 1) or several (Grade 1 and Grade 2; possibly even more if your specifications change later on).
Therefore, you need to create the series mappings dynamically. You'll have to group the source collection of custom objects by their Category2 values and then create the SeriesMapping
s, all of which must be done procedurally. I've attached a sample project based on the data you've provided.
Let me know if you need further assistance.
the Telerik team