Style a feature layer

Learn how to apply renderers and label definitions to a feature layer based on attribute values.

style a feature layer

Applications can display feature layer data with different styles to enhance the visualization. The type of Renderer you choose depends on your application. A SimpleRenderer applies the same symbol to all features, a UniqueValueRenderer applies a different symbol to each unique attribute value, and a ClassBreaksRenderer applies a symbol to a range of numeric values. Renderers are responsible for accessing the data and applying the appropriate symbol to each feature when the layer draws. You can also use a LabelDefinition to show attribute information for features. Visit the Styles and data visualization documentation to learn more about styling layers.

You can also author, style and save web maps, web scenes, and layers as portal items and then add them to the map in your application. Visit the following tutorials to learn more about adding portal items.

Display a web map
Display a web scene - [Add a feature layer from a portal item](xref://site.self/add-a-feature-layer-from-a-portal-item)

In this tutorial, you will apply different renderers to enhance the visualization of three feature layers with data for the Santa Monica Mountains: Trailheads with a single symbol, Trails based on elevation change and bike use, and Parks and Open Spaces based on the type of park.

Prerequisites

Before starting this tutorial, you should:

Have an ArcGIS account and an API key to access ArcGIS services. If you don't have an account, sign up for free.
Ensure your development environment meets the system requirements.

Optionally, you may want to install the ArcGIS Maps SDK for .NET to get access to project templates in Visual Studio (Windows only) and offline copies of the NuGet packages.

Steps

Open a Visual Studio solution

To start the tutorial, complete the Display a map tutorial or download and unzip the solution.
Open the .sln file in Visual Studio.

If you downloaded the solution project, set your API key.

An API Key enables access to services, web maps, and web scenes hosted in ArcGIS Online.

If necessary, set the API Key.

Go to your developer dashboard to get your API key. For these tutorials, use your default API key. It is scoped to include all of the services demonstrated in the tutorials.
In Visual Studio, in the Solution Explorer, click App.xaml.cs.

In the App class, add an override for the OnStartup() function to set the ApiKey property on ArcGISRuntimeEnvironment.

App.xaml.cs
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    public partial class App : Application
    {

        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            // Note: it is not best practice to store API keys in source code.
            // The API key is referenced here for the convenience of this tutorial.
            Esri.ArcGISRuntime.ArcGISRuntimeEnvironment.ApiKey = "YOUR_API_KEY";
        }

    }
}

If you are developing with Visual Studio for Windows, ArcGIS Maps SDK for .NET provides a set of project templates for each supported .NET platform. These templates provide all of the code needed for a basic Model-View-ViewModel (MVVM) app. Install the ArcGIS Maps SDK for .NET Visual Studio Extension to add the templates to Visual Studio (Windows only). See Install and set up for details.

Update the tutorial name used in the project (optional)

The Visual Studio solution, project, and the namespace for all classes currently use the name DisplayAMap. Follow the steps below if you prefer the name to reflect the current tutorial. These steps are not required, your code will still work if you keep the original name.

The tutorial instructions and code use the name StyleAFeatureLayer for the solution, project, and namespace. You can choose any name you like, but it should be the same for each of these.

Update the name for the solution and the project.
- In Visual Studio, in the Solution Explorer, right-click the solution name and choose Rename. Provide the new name for your solution.
- In the Solution Explorer, right-click the project name and choose Rename. Provide the new name for your project.
Rename the namespace used by classes in the project.
- In the Solution Explorer, expand the project node.
- Double-click MapViewModel.cs in the Solution Explorer to open the file.
- In the MapViewModel class, double-click the namespace name (DisplayAMap) to select it, and then right-click and choose Rename....
- Provide the new name for the namespace.
- Click Apply in the Rename: DisplayAMap window that appears in the upper-right of the code window. This will rename the namespace throughout your project.
Build the project.
- Choose Build > Build solution (or press <F6>).

Steps

Create a function to add a feature layer

A feature layer can be added from a feature service hosted in ArcGIS. Each feature layer contains features with a single geometry type (point, line, or polygon), and a set of attributes. Once added to the map, feature layers can be symbolized, styled, and labeled in a variety of ways.

You will define variables to store feature service URLs used by the app's layers and then create a helper method to add a layer to the map's collection of operational layers. You will use this code throughout the tutorial as you add and symbolize various layers.

In the Visual Studio > Solution Explorer, double-click MapViewModel.cs to open the file.
The project uses the Model-View-ViewModel (MVVM) design pattern to separate the application logic (view model) from the user interface (view). MapViewModel.cs contains the view model class for the application, called MapViewModel. See the Microsoft documentation for more information about the Model-View-ViewModel pattern.

Add additional required using statements near the top of the .cs file. Using statements make your code more concise by allowing you to use classes from these namespaces without having to fully qualify them.

MapViewModel.cs
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using System;
using System.Collections.Generic;
using System.Text;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using System.ComponentModel;
using System.Runtime.CompilerServices;

using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Mapping.Labeling;
using Esri.ArcGISRuntime.Symbology;
using System.Diagnostics;
using System.Drawing;

Create four static URIs: three for accessing feature layers, and a fourth for accessing a static image for use in a picture marker symbol. You will use these resources in future steps.

MapViewModel.cs
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    class MapViewModel : INotifyPropertyChanged
    {

        // Application constants used to connect to data and resources.
        static Uri parksAndOpenSpaces = new Uri("https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space/FeatureServer/0");
        static Uri trails = new Uri("https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails/FeatureServer/0");
        static Uri trailheads = new Uri("https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0");
        static Uri trailheadImage = new Uri("https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png");

Add a new method named AddFeatureLayer() that takes a feature service URI as an argument, creates a feature layer from it, and adds the layer to the map.

MapViewModel.cs
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        private Map? _map;
        public Map? Map
        {
            get { return _map; }
            set
            {
                _map = value;
                OnPropertyChanged();
            }
        }

        private FeatureLayer AddFeatureLayer(Uri featureServiceUri)
        {
            // Create a service feature table from a Uri.
            ServiceFeatureTable serviceFeatureTable = new ServiceFeatureTable(featureServiceUri);

            // Create a feature layer from the service feature table.
            FeatureLayer featureLayer = new FeatureLayer(serviceFeatureTable);

            // Add the feature layer to the maps operational layers collection.
            Map?.OperationalLayers.Add(featureLayer);

            // Return the feature layer.
            return featureLayer;
        }

Add a layer with a unique value renderer

Create a method to apply a different symbol for each type of park area to the Parks and Open Spaces feature layer.

Add a new method named AddOpenSpaceLayer() just after the newly added AddFeatureLayer() method.

UniqueValue assigns a symbol to a value or values. A unique value renderer uses a collection of unique values to assign the appropriate symbol for each feature it renderers.

For this example, the renderer uses a feature's TYPE attribute value to apply the correct symbol.

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        private void AddOpenSpaceLayer()
        {
            // Create a parks and open spaces feature layer and add it to the map view.
            FeatureLayer featureLayer = AddFeatureLayer(parksAndOpenSpaces);

            // Create fill symbols.
            SimpleFillSymbol purpleFillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Purple, null);
            SimpleFillSymbol greenFillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Green, null);
            SimpleFillSymbol blueFillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Blue, null);
            SimpleFillSymbol redFillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Red, null);

            // Create a unique value for natural areas, regional open spaces, local parks, and regional recreation parks.
            UniqueValue naturalAreas = new UniqueValue("Natural Areas", "Natural Areas", purpleFillSymbol, "Natural Areas");
            UniqueValue regionalOpenSpace = new UniqueValue("Regional Open Space", "Regional Open Space", greenFillSymbol, "Regional Open Space");
            UniqueValue localPark = new UniqueValue("Local Park", "Local Park", blueFillSymbol, "Local Park");
            UniqueValue regionalRecreationPark = new UniqueValue("Regional Recreation Park", "Regional Recreation Park", redFillSymbol, "Regional Recreation Park");

            // Create a unique value renderer to display these values.
            UniqueValueRenderer openSpacesUniqueValueRenderer = new UniqueValueRenderer
                (new List<string>() {
                    "TYPE"
                },
                new List<UniqueValue>() {
                    naturalAreas, regionalOpenSpace, localPark, regionalRecreationPark
                },
                "Open Spaces",
                null);

            // Assign the unique value renderer to the open spaces layer.
            featureLayer.Renderer = openSpacesUniqueValueRenderer;

            // Set the layer opacity to semi-transparent.
            featureLayer.Opacity = 0.2;
        }

Update SetupMap() to call the new AddOpenSpaceLayer() method.

MapViewModel.cs
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        private void SetupMap()
        {
            // Create a new map with a 'topographic vector' basemap.
            Map = new Map(BasemapStyle.ArcGISTopographic);

            AddOpenSpaceLayer();

        }

Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

When the app opens, Parks and Open Spaces feature layer is added to the map. The map displays the different types of parks and open spaces with four unique symbols.

Add a layer with a class breaks renderer

Create a method to apply a different symbol for each of the five ranges of elevation gain to the Trails feature layer.

Add a new method named AddTrailsLayer() just after the AddOpenSpaceLayer() method you created above.

A ClassBreak assigns a symbol to a range of values.

For this example, the renderer uses each feature's ELEV_GAIN attribute value to classify it into a defined range (class break) and apply the corresponding symbol.

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        private void AddTrailsLayer()
        {
            // Create a trails feature layer and add it to the map view.
            FeatureLayer featureLayer = AddFeatureLayer(trails);

            // Create simple line symbols.
            SimpleLineSymbol firstClassSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Purple, 3.0);
            SimpleLineSymbol secondClassSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Purple, 4.0);
            SimpleLineSymbol thirdClassSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Purple, 5.0);
            SimpleLineSymbol fourthClassSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Purple, 6.0);
            SimpleLineSymbol fifthClassSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Purple, 7.0);

            // Create five class breaks.
            ClassBreak firstClassBreak = new ClassBreak("Under 500", "0 - 500", 0.0, 500.0, firstClassSymbol);
            ClassBreak secondClassBreak = new ClassBreak("501 to 1000", "501 - 1000", 501.0, 1000.0, secondClassSymbol);
            ClassBreak thirdClassBreak = new ClassBreak("1001 to 1500", "1001 - 1500", 1001.0, 1500.0, thirdClassSymbol);
            ClassBreak fourthClassBreak = new ClassBreak("1501 to 2000", "1501 - 2000", 1501.0, 2000.0, fourthClassSymbol);
            ClassBreak fifthClassBreak = new ClassBreak("2001 to 2300", "2001 to 2300", 2001.0, 2300.0, fifthClassSymbol);
            List<ClassBreak> elevationBreaks = new List<ClassBreak>() { firstClassBreak, secondClassBreak, thirdClassBreak, fourthClassBreak, fifthClassBreak };

            // Create and assign a class breaks renderer to the feature layer.
            ClassBreaksRenderer elevationClassBreaksRenderer = new ClassBreaksRenderer("ELEV_GAIN", elevationBreaks);
            featureLayer.Renderer = elevationClassBreaksRenderer;

            // Set the layer opacity to semi-transparent.
            featureLayer.Opacity = 0.75;
        }

Update SetupMap() to call the new AddTrailsLayer() method.

MapViewModel.cs
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        private void SetupMap()
        {
            // Create a new map with a 'topographic vector' basemap.
            Map = new Map(BasemapStyle.ArcGISTopographic);

            AddOpenSpaceLayer();

            AddTrailsLayer();

        }

Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

When the app opens, the Trails feature layer is added to the map. The map displays trails with different symbols depending on trail elevation.

Add layers with definition expressions

You can use a definition expression to define a subset of features to display. Features that do not meet the expression criteria are not displayed by the layer. In the following steps, you will create two methods that use a definition expression to apply a symbol to a subset of features in the Trails feature layer.

FeatureLayer.DefinitionExpression uses a SQL expression to limit the features available for query and display. Your code will create two layers that each display a different subset of trails based on the value for the `USE_BIKE` field. Trails that allow bikes will be symbolized with a blue symbol (`"USE_BIKE = 'Yes'"`) and those that don't will be red (`"USE_BIKE = 'No'"`). Another way to symbolize these features would be to create a UniqueValueRenderer that applies a different symbol for these values.

Add a method named AddBikeOnlyTrailsLayer() with a definition expression to filter for trails that permit bikes. Add this method just after the newly added AddTrailsLayer() method.

MapViewModel.cs
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        private void AddBikeOnlyTrailsLayer()
        {
            // Create a trails feature layer and add it to the map view.
            FeatureLayer featureLayer = AddFeatureLayer(trails);

            // Write a definition expression to filter for trails that permit the use of bikes.
            featureLayer.DefinitionExpression = "USE_BIKE = 'Yes'";

            // Create and assign a simple renderer to the feature layer.
            SimpleLineSymbol bikeTrailSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Dot, Color.Blue, 2.0);
            SimpleRenderer bikeTrailRenderer = new SimpleRenderer(bikeTrailSymbol);
            featureLayer.Renderer = bikeTrailRenderer;
        }

Add another method named AddNoBikeTrailsLayer() with a definition expression to filter for trails that don't allow bikes. Add this method just after the AddBikeOnlyTrailsLayer() method.

MapViewModel.cs
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        private void AddNoBikeTrailsLayer()
        {
            // Create a trails feature layer and add it to the map view.
            FeatureLayer featureLayer = AddFeatureLayer(trails);

            // Write a definition expression to filter for trails that don't permit the use of bikes.
            featureLayer.DefinitionExpression = "USE_BIKE = 'No'";

            // Create and assign a simple renderer to the feature layer.
            SimpleLineSymbol noBikeTrailSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Dot, Color.Red, 2.0);
            SimpleRenderer noBikeTrailRenderer = new SimpleRenderer(noBikeTrailSymbol);
            featureLayer.Renderer = noBikeTrailRenderer;
        }

Update SetupMap() to call the new AddBikeOnlyTrailsLayer() and AddNoBikeTrailsLayer() methods.

MapViewModel.cs
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        private void SetupMap()
        {
            // Create a new map with a 'topographic vector' basemap.
            Map = new Map(BasemapStyle.ArcGISTopographic);

            AddOpenSpaceLayer();

            AddTrailsLayer();

            AddNoBikeTrailsLayer();

            AddBikeOnlyTrailsLayer();

        }

Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

When the app opens, two Trails feature layers are added to the map. One shows where bikes are permitted and the other where they are prohibited.

Symbolize a layer with a picture symbol and label features with an attribute

Create a method to style trailheads with hiker images and labels for the Trailheads feature layer.

Feature layers, graphics overlays, and map image layer sublayers in your app can be labeled using a combination of attribute values, text strings, and values calculated with an expression. You can determine how labels are positioned and prioritized, and how conflicts between overlapping labels are automatically and dynamically resolved.

For feature layers, graphics overlays, and map image sublayers, labeling is implemented using a collection of LabelDefinition objects to define what labels look like (font, size, color, angle, and so on), the scale at which they display, the text they contain, how they handle overlaps, and so on.

If you want to label everything in your layer or overlay to look identical, you can define a single label definition. If you want to use different label formatting for different attribute values, you can add as many label definitions as you need to define distinct sets of geoelements for labeling.

Create a helper method named MakeLabelDefinition() to define a label definition based on the feature layer attribute that's passed in. The function will also define the label placement and text symbol. Add this method just after the AddNoBikeTrailsLayer() method you created earlier.

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        private LabelDefinition MakeLabelDefinition(string labelAttribute)
        {
            // Create a new text symbol.
            TextSymbol labelTextSymbol  = new TextSymbol
            {
                Color = Color.White,
                Size = 12.0,
                HaloColor = Color.Red,
                HaloWidth = 1.0,
                FontFamily = "Arial",
                FontStyle = FontStyle.Italic,
                FontWeight = FontWeight.Normal
            };

            // Create a new Arcade label expression based on the field name.
            ArcadeLabelExpression labelExpression = new ArcadeLabelExpression("$feature." + labelAttribute);

            // Create and return the label definition.
            return new LabelDefinition(labelExpression, labelTextSymbol );
        }

Add a method named AddTrailheadsLayer(). Add this method just after the new MakeLabelDefinition() method.

Use a PictureMarkerSymbol to draw a trailhead hiker image. Use the LabelDefinition to label each trailhead by its name.

MapViewModel.cs
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        private void AddTrailheadsLayer()
        {
            // Create a trailheads feature layer and add it to the map view.
            FeatureLayer featureLayer = AddFeatureLayer(trailheads);

            // Create a new picture marker symbol that uses the trailhead image.
            PictureMarkerSymbol pictureMarkerSymbol = new PictureMarkerSymbol(trailheadImage);
            pictureMarkerSymbol.Height = 18.0;
            pictureMarkerSymbol.Width = 18.0;

            // Create a new simple renderer based on the picture marker symbol.
            SimpleRenderer simpleRenderer = new SimpleRenderer(pictureMarkerSymbol);

            // Set the feature layer's renderer and enable labels.
            featureLayer.Renderer = simpleRenderer;
            featureLayer.LabelsEnabled = true;

            // Create the label definition and pass the "TRL_NAME" attribute to label features by trail name.
            LabelDefinition trailHeadsDefinition = MakeLabelDefinition("TRL_NAME");

            // Add the label definition to the layer's label definition collection.
            featureLayer.LabelDefinitions.Add(trailHeadsDefinition);
        }

Update SetupMap() to call the new AddTrailheadsLayer() method.

MapViewModel.cs
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        private void SetupMap()
        {
            // Create a new map with a 'topographic vector' basemap.
            Map = new Map(BasemapStyle.ArcGISTopographic);

            AddOpenSpaceLayer();

            AddTrailsLayer();

            AddNoBikeTrailsLayer();

            AddBikeOnlyTrailsLayer();

            AddTrailheadsLayer();

        }
Expand

Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

When the app opens, all the layers you've created and symbolized are displayed on the map.

Parks and open spaces are displayed with four unique symbols
Trails use different symbols (line widths) depending on trail elevation
Trails are blue where bikes are permitted and red where they are prohibited
Trailheads are displayed with a hiker icon and labels display each trail's name

What's next?

Learn how to use additional API features, ArcGIS location services, and ArcGIS tools in these tutorials:

ArcGIS Maps SDK for .NET

Style a feature layer

Solution

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