public class PieChartRendererDefinition : ChartRendererDefinition 

/// <summary>
/// Renders a feature layer using Pie chart symbols to represent data
/// ![Pie chart renderer](https://ArcGIS.github.io/arcgis-pro-sdk/images/Renderers/pie-chart.png)
/// </summary>
{
  //Check feature layer name
  //Code works with the USDemographics feature layer available with the ArcGIS Pro SDK Sample data
  var featureLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault(f => f.Name == "USDemographics");
  if (featureLayer == null)
  {
    MessageBox.Show("This renderer works with the USDemographics feature layer available with the ArcGIS Pro SDK Sample data", "Data missing");
  }
  //Note: Run within a QueuedTask
  //Fields to use for the pie chart slices
  var chartFields = new List<string>
  {
          "WHITE10",
           "BLACK10",
           "AMERIND10",
           "ASIAN10",
           "HISPPOP10",
           "HAMERIND10",
           "HWHITE10",
           "HASIAN10",
           "HPACIFIC10",
           "HBLACK10",
            "HOTHRACE10"
  };

  PieChartRendererDefinition pieChartRendererDefn = new PieChartRendererDefinition()
  {
    ChartFields = chartFields,
    ColorRamp = colorRamp,
    SizeOption = PieChartSizeOptions.Field,
    FieldName = "BLACK10",
    FixedSize = 36.89,
    DisplayIn3D = true,
    ShowOutline = true,
    Orientation = PieChartOrientation.CounterClockwise,
  };
  //Creates a "Renderer"
  var pieChartRenderer = featureLayer.CreateRenderer(pieChartRendererDefn);

  //Sets the renderer to the feature layer
  featureLayer.SetRenderer(pieChartRenderer);
}