You can take a look at the Sorting
help article and see if this will work for you.
Note that the RadChart is our old charting component which has many known limitations and issues. This is why we created the new RadChartView
which has better implementation and improved performance. The new controls are also very flexible and easier to set up. You can read about the differences between the charts in the RadChart vs. RadChartView
help article. If you just start using a charting control in your application or its integration its not very complex I recommend you to use RadChartView instead. The chartview doesn't have a built-in functionality but you can sort your data before pass it in its series' ItemsSource. I attached a sample project demonstrating this approach. Please give it a try and let me know if it helps.
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