Thank you for your question.
Chart legends are currently not implemented. Considering the XAML richness we decided to delay that feature and to collect user feedback first. You can very easily add your own legend by putting three ellipses (or whatever visual you find most appropriate) in a stack panel. In fact we are using the very same approach in our chart examples in the Demo application, available in the installation package.
We will soon have a PITS section for Windows Phone and you will be able to vote for your favorite features you would like to see implemented.
Do not hesitate to write us back should you have any other questions/problems related with our tools.
the Telerik team
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