Add a feature layer from a portal item

Before starting this tutorial:

• You need an ArcGIS Location Platform or ArcGIS Online account.

• 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.

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 The ArcGIS Basemap Styles service, also referred to as the Basemap Styles service, is a location service that provides basemap styles and data for the world. It returns styles as Mapbox styles and web maps, and data as vector tiles and/or map tiles. It supports all of the styles in the ArcGIS Basemap style and Open Basemap style family. An ArcGIS Location Platform or ArcGIS Online account is required to use the service. Learn more .

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 An item, also known as a content item, is a resource stored in a portal such as a web map, hosted layer, style, script tool, file, or notebook. Learn more (such as a web map or feature layer) hosted in a portal (such as ArcGIS Online) using its unique item ID An item ID is a unique identifier representing a single item stored, managed, and accessed in a portal, such as a web map, hosted layer, or file. Learn more . 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

   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

           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;
   
           }
   Why use async and Task?

   When calling methods asynchronously inside a function (using the await keyword), the async keyword is required in the signature.

   Although a void return type would continue to work, this is not considered best practice. Exceptions thrown by an async void method cannot be caught outside of that method, are difficult to test, and can cause serious side effects if the caller is not expecting them to be asynchronous. The only circumstance where async void is acceptable is when using an event handler, such as a button click.

   See the Microsoft documentation for more information about Asynchronous programming with async and await.

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.

   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

           public MapViewModel()
           {
   
               _ = SetupMap();
   
           }
   What is a discard?

   From the Microsoft documentation:

   “[Discards] are placeholder variables that are intentionally unused in application code. Discards are equivalent to unassigned variables; they don’t have a value. A discard communicates intent to the compiler and others that read your code: You intended to ignore the result of an expression.”

5. Add code to the SetupMap() function to create a PortalItem object that references the feature layer portal item An item, also known as a content item, is a resource stored in a portal such as a web map, hosted layer, style, script tool, file, or notebook. Learn more . To do this, provide the item ID An item ID is a unique identifier representing a single item stored, managed, and accessed in a portal, such as a web map, hosted layer, or file. Learn more and an ArcGISPortal object.

   MapViewModel.cs

           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

   58 collapsed lines
   //   Copyright 2021 Esri
   //   Licensed under the Apache License, Version 2.0 (the "License");
   //   you may not use this file except in compliance with the License.
   //   You may obtain a copy of the License at
   //
   //   https://www.apache.org/licenses/LICENSE-2.0
   //
   //   Unless required by applicable law or agreed to in writing, software
   //   distributed under the License is distributed on an "AS IS" BASIS,
   //   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   //   See the License for the specific language governing permissions and
   //   limitations under the License.
   
   
   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;
   
   
   namespace AddAFeatureLayerFromAPortalItem
   {
   
       class MapViewModel : INotifyPropertyChanged
       {
   
           public MapViewModel()
           {
   
               _ = SetupMap();
   
           }
   
   
           public event PropertyChangedEventHandler? PropertyChanged;
           protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
           {
               PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
           }
   
           private Map? _map;
           public Map? Map
           {
               get { return _map; }
               set
               {
                   _map = value;
                   OnPropertyChanged();
               }
           }
   
   
           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);
   
           }
   4 collapsed lines
   
       }
   
   }

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.

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 ArcGIS Location Services, also referred to as Location Services, are services hosted by Esri that provide geospatial functionality for developing mapping applications. They include the ArcGIS Basemap Styles service, ArcGIS Static Basemap Tiles service, ArcGIS Places service, ArcGIS Geocoding service, ArcGIS Routing service, ArcGIS GeoEnrichment service, and ArcGIS Elevation service. An ArcGIS Location Platform or ArcGIS Online account is required to use the services. Learn more used in this tutorial, you must implement API key authentication API key authentication is a type of authentication that uses an API key to authenticate requests to ArcGIS services and secure portal items. Learn more or user authentication User authentication is a type of authentication that allows users with an ArcGIS account to sign into an application and allow it to access ArcGIS content, services, and resources on their behalf. The typical authorization protocol used is OAuth2.0. Learn more using an ArcGIS Location Platform An ArcGIS Location Platform account, formerly known as an ArcGIS Developer account, is an identity associated with an ArcGIS Location Platform subscription. Learn more or an ArcGIS Online An ArcGIS Online account, also known as an ArcGIS Organization account, is an identity associated with an ArcGIS Online subscription. It can be used to access ArcGIS tools and develop applications with ArcGIS location services for an organization. Learn more account.

To complete this tutorial, click on the tab in the switcher below for your authentication type of choice, either API key authentication or User authentication.

Set developer credentials in the solution

To allow your app users to access ArcGIS location services ArcGIS Location Services, also referred to as Location Services, are services hosted by Esri that provide geospatial functionality for developing mapping applications. They include the ArcGIS Basemap Styles service, ArcGIS Static Basemap Tiles service, ArcGIS Places service, ArcGIS Geocoding service, ArcGIS Routing service, ArcGIS GeoEnrichment service, and ArcGIS Elevation service. An ArcGIS Location Platform or ArcGIS Online account is required to use the services. Learn more , use the developer credentials that you created in the Set up authentication step to authenticate requests for resources.

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.