RadControls for ASP.NET AJAX LegendDisplayMode - this series.Appearance property will define what will be shown in the legend for each chart series. The valid values are from the ChartSeriesLegendDisplayMode enumeration.
Nothing - the legend will not display information for this series
SeriesName - the legend will display a single item for each series, this item will show the series name
ItemLabels - the legend will display an item for each series item (the preferred setting for pie charts). Note, that although it is ItemLabels, the legend will actually display the value of the item Name property, thus providing means to show a different information from what is shown in the item labels.
Here is a pie chart with a single series with LegendDisplayMode set to "ItemLabels":