1、設定餅圖顯示樣式
//設定Legend的樣式
_pieSeries.LegendPointOptions.PointView = PointView.ArgumentAndValues;
_pieSeries.LegendPointOptions.Pattern = "{A}: {VP:P2}";
//設定Label的樣式
label.Position = PieSeriesLabelPosition.Inside;
label.TextPattern = "{A}: {VP:P2}";

2、設定餅圖顯示百分比或者數值

public static class ExtensionClass
{
/// <summary>
/// 設定餅狀Series顯示方式（值/百分比）
/// </summary>
/// <param name="series">Series</param>
public static void SetPiePercentage(this Series series)
{
    if (series.View is PieSeriesView)
    {
        //設定為值
        //((PiePointOptions)series.PointOptions).PercentOptions.ValueAsPercent = false;
        //((PiePointOptions)series.PointOptions).ValueNumericOptions.Format = NumericFormat.Number;
        //((PiePointOptions)series.PointOptions).ValueNumericOptions.Precision = 0;
        //設定為百分比
        ((PiePointOptions)series.PointOptions).PercentOptions.ValueAsPercent = true;
        ((PiePointOptions)series.PointOptions).ValueNumericOptions.Format = NumericFormat.Percent;
        ((PiePointOptions)series.PointOptions).ValueNumericOptions.Precision = 0;
        }
    }
}