Add a feature layer from a portal item

Learn how to use an ArcGIS portal item to access and display a feature layer in a map.

add a feature layer from a portal item

You can host a variety of geographic data and other resources using ArcGIS Online. These portal items can also define how the data is presented. A web map or web scene, for example, not only defines the layers for a map or scene, but also how layers are symbolized, the minimum and/or maximum scales at which they display, and several other properties. Likewise, a hosted feature layer contains the data for the layer and also defines the symbols and other display properties for how it is presented. When you add a map, scene, or layer from a portal item to your app, everything that has been saved with the item is applied in your app. Adding portal items to your app rather than creating them programmatically saves you from writing a lot of code, and can provide consistency across apps that use the same data.

In this tutorial, you will add a hosted feature layer to display trailheads in the Santa Monica Mountains of Southern California. The hosted layer defines the trailhead locations (points) as well as the symbols used to display them.

Prerequisites

Before starting this tutorial:

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.

Develop or download

You have two options for completing this tutorial:

  1. Option 1: Develop the code or
  2. Option 2: Download the completed solution

Option 1: Develop the code

To start the tutorial, complete the Display a map tutorial. This creates a map to display the Santa Monica Mountains in California using the topographic basemap from the ArcGIS basemap styles service.

Open a Visual Studio solution

  1. Open the Visual Studio solution you created by completing the Display a map tutorial.
  2. Continue with the following instructions to display a feature layer hosted in an ArcGIS portal in your map.

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.

Display the ArcGIS portal item

You can reference an item (such as a web map or feature layer) hosted in a portal (such as ArcGIS Online) using its unique item ID. You will reference the Trailheads Styled feature layer stored in ArcGIS Online using its item ID of: 2e4b3df6ba4b44969a3bc9827de746b3. You will then add that feature layer to your map's collection of data layers (operational layers).

  1. In Visual Studio, in the Solution Explorer, double-click MapViewModel.cs to open the file.

  2. Add additional required using statements near the top of the class file.

    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.Portal;
    using System.Threading.Tasks;
    
  3. Modify the signature of the SetupMap() function to include the async keyword and to return Task rather than void.

    MapViewModel.cs
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            private async Task SetupMap()
            {
    
                // Create a new map with a 'topographic vector' basemap.
                var map = new Map(BasemapStyle.ArcGISTopographic);
    
                // Set the initial viewpoint around the Santa Monica Mountains in California.
                var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
                map.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
    
                // Set the view model's Map property with the map.
                Map = map;
    
            }
    
  4. In the MapViewModel constructor, modify the call to SetupMap() to avoid a compilation warning. After changing SetupMap() to an asynchronous method, the following warning appears in the Visual Studio Error List.

    Use dark colors for code blocksCopy
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    Because this call is not awaited, execution of the current method continues before the call is
    completed. Consider applying the 'await' operator to the result of the call.

    Because your code does not anticipate a return value from this call, the warning can be ignored. To be more specific about your intentions with this call and to address the warning, add the following code to store the return value in a discard.

    MapViewModel.cs
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            public MapViewModel()
            {
    
                _ = SetupMap();
    
            }
    
  5. Add code to the SetupMap() function to create a PortalItem object that references the feature layer portal item. To do this, provide the item ID and an ArcGISPortal object.

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            private async Task SetupMap()
            {
    
                // Create a new map with a 'topographic vector' basemap.
                var map = new Map(BasemapStyle.ArcGISTopographic);
    
                // Set the initial viewpoint around the Santa Monica Mountains in California.
                var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
                map.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
    
                // Set the view model's Map property with the map.
                Map = map;
    
                // Create an ArcGIS Portal object.
                ArcGISPortal portal = await ArcGISPortal.CreateAsync();
    
                // Create a portal item from the ArcGIS Portal object using a portal item string.
                PortalItem portalItem = await PortalItem.CreateAsync(portal, "2e4b3df6ba4b44969a3bc9827de746b3");
    
            }
    
  6. Create a FeatureLayer using the PortalItem which loads it asynchronously. Then add the feature layer to the Map's operational layers collection.

    MapViewModel.cs
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            private async Task SetupMap()
            {
    
                // Create a new map with a 'topographic vector' basemap.
                var map = new Map(BasemapStyle.ArcGISTopographic);
    
                // Set the initial viewpoint around the Santa Monica Mountains in California.
                var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
                map.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
    
                // Set the view model's Map property with the map.
                Map = map;
    
                // Create an ArcGIS Portal object.
                ArcGISPortal portal = await ArcGISPortal.CreateAsync();
    
                // Create a portal item from the ArcGIS Portal object using a portal item string.
                PortalItem portalItem = await PortalItem.CreateAsync(portal, "2e4b3df6ba4b44969a3bc9827de746b3");
    
                // Create a feature layer from the portal item and specify a numerical layer id (i.e. 0).
                FeatureLayer layer = new FeatureLayer(portalItem, 0);
    
                // Add the layer to the operational layer of the map.
                map.OperationalLayers.Add(layer);
    
            }
    
    Expand
  7. Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app. If your app uses user authentication, enter your ArcGIS Online credentials when prompted.

You should see a map of trail heads in the Santa Monica mountains. Click, drag, and scroll the mouse wheel on the map view to explore the map.

Alternatively, you can download the tutorial solution, as follows.

Option 2: Download the solution

  1. Click the Download solution link in the right-hand panel of the page.

  2. Unzip the file to a location on your machine.

  3. Open the .sln file in Visual Studio.

Since the downloaded solution does not contain authentication credentials, you must first set up authentication to create credentials, and then add the developer credentials to the solution.

Set up authentication

To access the secure ArcGIS location services used in this tutorial, you must implement API key authentication or user authentication using an ArcGIS Location Platform or an ArcGIS Online account.

Create a new API key access token with privileges to access the secure resources used in this tutorial.

  1. Complete the Create an API key tutorial and create an API key with the following privilege(s):

    • Privileges
      • Location services > Basemaps
  2. Copy and paste the API key access token into a safe location. It will be used in a later step.

Set developer credentials in the solution

To allow your app users to access ArcGIS location services, use the developer credentials that you created in the Set up authentication step to authenticate requests for resources.

  1. In Visual Studio, in the Solution Explorer, click App.xaml.cs to open the file.

  2. Set the ArcGISEnvironment.ApiKey property with your API key access token.

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            protected override void OnStartup(StartupEventArgs e)
            {
                base.OnStartup(e);
    
                // Set the access token for ArcGIS Maps SDK for .NET.
                Esri.ArcGISRuntime.ArcGISRuntimeEnvironment.ApiKey = "YOUR_ACCESS_TOKEN";
    
                // Call a function to set up the AuthenticationManager for OAuth.
                UserAuth.ArcGISLoginPrompt.SetChallengeHandler();
    
            }
    
  3. Remove the code that sets up user authentication.

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            protected override void OnStartup(StartupEventArgs e)
            {
                base.OnStartup(e);
    
                // Set the access token for ArcGIS Maps SDK for .NET.
                Esri.ArcGISRuntime.ArcGISRuntimeEnvironment.ApiKey = "YOUR_ACCESS_TOKEN";
    
                // Call a function to set up the AuthenticationManager for OAuth.
                UserAuth.ArcGISLoginPrompt.SetChallengeHandler();
    
            }
    

Best Practice: The access token is stored directly in the code as a convenience for this tutorial. Do not store credentials directly in source code in a production environment.

Run the solution

Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app. If your app uses user authentication, enter your ArcGIS Online credentials when prompted.

You should see a map of trail heads in the Santa Monica mountains. Click, drag, and scroll the mouse wheel on the map view to explore the map.

What's next?

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

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