public class UniqueValueRendererDefinition : RendererDefinition 

await QueuedTask.Run(() =>
{
  var fields = new List<string> { "Type" }; //field to be used to retrieve unique values
  CIMPointSymbol pointSym = SymbolFactory.Instance.ConstructPointSymbol(
      ColorFactory.Instance.GreenRGB, 16.0, SimpleMarkerStyle.Pushpin);  //constructing a point symbol as a template symbol
  CIMSymbolReference symbolPointTemplate = pointSym.MakeSymbolReference();

  //constructing renderer definition for unique value renderer
  UniqueValueRendererDefinition uniqueValueRendererDef =
new UniqueValueRendererDefinition(fields, symbolPointTemplate);

  //creating a unique value renderer
  var flyr = MapView.Active.GetSelectedLayers()[0] as FeatureLayer;
  CIMUniqueValueRenderer uniqueValueRenderer = flyr.CreateRenderer(uniqueValueRendererDef) as CIMUniqueValueRenderer;

  //setting the renderer to the feature layer
  flyr.SetRenderer(uniqueValueRenderer);
});

var uvrDef = new UniqueValueRendererDefinition()
{
  ValueFields = new List<string> { "ACTYPE" },
  SymbolTemplate = SymbolFactory.Instance.ConstructPointSymbol(
    ColorFactory.Instance.RedRGB, 10, SimpleMarkerStyle.Hexagon)
      .MakeSymbolReference(),
  ValuesLimit = 5
};
//Note: CreateRenderer can only create value classes based on
//the current events it has received
streamLayer.SetRenderer(streamLayer.CreateRenderer(uvrDef));