I have attached a sample project, where you can find an implementation of dynamic adding of Annotation to the ChartView by user click.
There are some things which you can take into consideration. TheChartView has an event MouseLeftButtonDownwhich you can use for adding the Annotation to the ChartView. If you want to add it to the current position of the mouse, you should use ConvertPointToData method, which takes a System.Windows.Point as an argument (position on the screen) and returns an object of type DataTuple.
The two properties of the DataTuple class (FirstValue and SecondValue) represent the coordinates on the Horizontal and the Vertical axes of the RadCartesianChart.
I hope this helps.
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