I have added your idea to the PITS - a property that can be used for databinding the name of each series item in the same manner in which ColorField can be. You can monitor its progress and vote for it in this URL
Regarding your exact scenario - I am afraid I still cannot understand the limitation. The DataFormatString for labels or tooltips of the series can use the YValue of the item at present and whether this property is set in the code-behind or in the markup there is no difference. The idea that more columns from a datasource can be added to a tooltip/label is logged in this PITS item
, so you may find it interesting as well.
I believe my previous sample shows a relatively easy workaround for the time being that can enable you to use markup declaration for all common properties and only create items programmatically. Simply add the DataField="color" property to the LabelsAppearance tag of the PieSeries declaration and you will see the strings around the pie.
All the best,
the Telerik team
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