public class UniqueValueRendererDefinition : RendererDefinition 

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

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

    //creating a unique value renderer
    CIMUniqueValueRenderer uniqueValueRenderer = featureLayer.CreateRenderer(uniqueValueRendererDef) as CIMUniqueValueRenderer;

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

/// <summary>
/// Renders a feature layer using unique values from one or multiple fields
/// ![Unique Value renderer](https://ArcGIS.github.io/arcgis-pro-sdk/images/Renderers/unique-value.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");
  }
  //construct unique value renderer definition                
  UniqueValueRendererDefinition uvr = new
           UniqueValueRendererDefinition()
  {
    //Refer to the function below to get a display field of the feature layer
    ValueFields = new List<string> { GetDisplayField(featureLayer) }, //multiple fields in the array if needed.
    ColorRamp = colorRamp, //Specify color ramp
  };

  //Creates a "Renderer"
  var cimRenderer = featureLayer.CreateRenderer(uvr);

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

  //Function to get the display field of a feature layer
  static string GetDisplayField(FeatureLayer featureLayer)
  {
    // get the CIM definition from the layer
    var cimFeatureDefinition = featureLayer.GetDefinition() as ArcGIS.Core.CIM.CIMBasicFeatureLayer;
    // get the view of the source table underlying the layer
    var cimDisplayTable = cimFeatureDefinition.FeatureTable;
    // this field is used as the 'label' to represent the row
    return cimDisplayTable.DisplayField;
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    streamLayer = null;
    //https://geoeventsample1.esri.com:6443/arcgis/rest/services/AirportTraffics/StreamServer

    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));
  }
}