I have a chart with an observablecollections with a custom class with 4-5 fields. Couple of fields map to the XValue and YValue and the others are to identify the datapoint. In the BuildCustomItemStyle method I use the dataseries to get all fields bound to the datapoint via
(dataSeries[(item as BaseChartItem).CurrentIndex].DataItem
However if I exceed 200 datapoints on the chart the information doesn't exist anymore and I am unable to access the fields. Also I tried to bind one of my fields to LegendLabel and extract it as well. Though this works for a limited number of datapoints on the chart and doesn't bind if the datapoints increase in number.

Hi scorp,

One possible cause for this behavior may be the sampling. For more information on this feature, please refer to this article:

http://www.telerik.com/help/silverlight/radchart-features-sampling.html

You can set the SamplingThreshold to 0, to see if the data is available. If it is not, you can open a formal support ticket, and send us a small working project, for additional review and testing.

Kind regards,
Yavor
the Telerik team