How to edit symbol labels of a feature layer?

[Anonymous User]

I'm looking for a way to programmatically edit the symbol labels of my feature layer (the labels that appear in the table of contents / legend):

For example, let's say I'm assigning a simple unique value renderer to my layer based on a single field:

var fields = new[] {"RENDITION"};
var rendererDef = new UniqueValueRendererDefinition(fields);
var renderer = layer.CreateRenderer(rendererDef);
layer.SetRenderer(renderer);

Is there a way I can then define the labels for these unique symbols?

[CharlesMacleod · Accepted solution]

Hi Luke,

We have to edit the unique value renderer itself, once it has been made. I have provided some code below. Note: I encourage you to look at the samples for the CIM at https://github.com/esri/arcgis-pro-sdk-community-samples/tree/master/Map-Authoring/CIMExamples. I based the code snippet below on the source code in 'CreateCIMRendererFromScratch.cs'. It uses the U.S. States dataset available with the samples.

internal class SetLabelsOnUniqueValueRenderer : Button {

        protected async override void OnClick() {

            var usStatesLayer =

                MapView.Active.Map.GetLayersAsFlattenedList().FirstOrDefault((fl) => fl.Name == "States") as

                    FeatureLayer;

            if (usStatesLayer == null) {

                MessageBox.Show("Please add the 'States' layer to the TOC - with a 'STATE_NAME' field containing state names.", "Cannot find US States");

                return;

            }

            //make a unique value renderer

            await CreateUniqueValueRendererOnStatesAsync(usStatesLayer);

            SetLabelsOnStatesRendererAsync(usStatesLayer);

        }

        private Task CreateUniqueValueRendererOnStatesAsync(FeatureLayer fl) {

            return QueuedTask.Run(() => {

                var uvrDef = new UniqueValueRendererDefinition() {

                    ValueFields = new string[] {"STATE_ABBR"},

                    SymbolTemplate = SymbolFactory.DefaultPolygonSymbol.MakeSymbolReference(),

                    //Simple ramp

                    ColorRamp = new CIMLinearContinuousColorRamp() {

                        FromColor = CIMColor.CreateRGBColor(0, 255, 0, 60),//Green, partially transparent

                        ToColor = CIMColor.CreateRGBColor(255, 0, 0, 60),//Red,  partially transparent

                        ColorSpace = new CIMICCColorSpace() {

                            URL = "Default RGB"

                        }

                    }

                };

                fl.SetRenderer(fl.CreateRenderer(uvrDef));

            });

        }

        private Task SetLabelsOnStatesRendererAsync(FeatureLayer fl) {

            return QueuedTask.Run(() => {

                var renderer = fl.GetRenderer() as CIMUniqueValueRenderer;

                //A UniqueValue renderer has one or more CIMUniqueValueGroups. In this example

                //there is only one CIMUniqueValueGroup (otherwise use a 'foreach(var group in ....)'

                var group = renderer.Groups[0];

                //Each group has one or more CIMUniqueValueClasses - in this case we have one class per

                //STATE_ABBR value. Note: The default value and label are on the renderer itself

                //(renderer.DefaultLabel, renderer.DefaultSymbol) and are NOT in a class.

                foreach (var valClass in group.Classes) {

                    //Each CIMUniqueValueClass has a Label (what you are after 😉 and an array of CIMUniqueValues

                    //As our values are unique, we have one CIMUniqueValue per class.

                    //Get its field value (read from STATE_ABBR) and change the label to be the state name

                    if (valClass.Values[0].FieldValues[0] == "AK")

                        valClass.Label = "Alaska";

                    else if (valClass.Values[0].FieldValues[0] == "AL")

                        valClass.Label = "Alabama";

                    else if (valClass.Values[0].FieldValues[0] == "AR")

                        valClass.Label = "Arkansas";

                    else if (valClass.Values[0].FieldValues[0] == "AZ")

                        valClass.Label = "Arizona";

                    //etc,etc

                }

                fl.SetRenderer(renderer);

            });

        }

    }

[Anonymous User]

Just what I was looking for. Thanks Charles.