There is no designated property for this purpose. You have already found the workaround -- use XValue2 or any other unused ChartSeriesItem property - YValue2, YValue3, YValue4, Name, Label. Note, that if you use the Label property the ID will appear as a label, so this would be suitable only if you do not plan to show item labels. In a similar way -- you can use the Name property only if it is OK to let the ID appear in the legend (usually in a pie chart with LegendDisplayMode = "ItemLabels") or if the legend is hidden.
Hope this helps.
the Telerik team
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