Display a web map

Learn how to create and display a map from a web map stored in ArcGIS.

A web map contains the definition of a map, including properties such as the basemap, initial extent, layers, styles, pop-ups, and labels. You can author and save web maps using the Map Viewer or ArcGIS Pro and share them in ArcGIS. Each web map is stored as an item in ArcGIS Online or ArcGIS Enterprise, allowing you to access a web map from a portal using its item ID and display it in your app.

In this tutorial, you use a web map's item ID to display a map of trails, trailheads and parks in the Santa Monica Mountains. The web map is hosted in ArcGIS Online.

Prerequisites

Steps

Open the Visual Studio solution

1. To start the tutorial, complete the Display a map tutorial or download and unzip the solution.

2. Open the .sln file in Visual Studio.

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

   Instructions for setting the API key

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

   If necessary, set the API Key.

   1. 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.

   2. In Visual Studio, in the Solution Explorer, click App.xaml.cs.

   3. 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";
              }
      
          }
      }

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.

Get the web map item ID

You can use ArcGIS tools to create and view web maps. Use the Map Viewer to identify the web map item ID. This item ID will be used later in the tutorial.

1. Go to the LA Trails and Parks web map in the Map Viewer in ArcGIS Online. This web map displays trails, trailheads and parks in the Santa Monica Mountains.
2. Make a note of the item ID at the end of the browser's URL. The item ID should be 41281c51f9de45edaf1c8ed44bb10e30

Display the web map

You can display a web map using the web map's item ID. Create a map from the web map portal item, and display it in your app.

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

1. Add additional required using statements at the top of the class.

   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;
   

2. In the MapViewModel class, remove all the existing code in the SetupMap() function.

   MapViewModel.cs

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

3. Modify the signature of the SetupMap() function to include the async keyword and return Task rather than void.

   MapViewModel.cs

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           private async Task SetupMap()
           {
   
           }
   

   Expand
   More info

   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. Modify the call to SetupMap() (in the MapViewModel constructor) to avoid a compilation warning. After changing SetupMap() to an asynchronous method, the following warning appears in the Visual Studio Error List.

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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();
   
           }
   

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   More info

   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 for the web map. To do this, provide the web map's item ID and an ArcGISPortal referencing ArcGIS Online.

   MapViewModel.cs

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           private async Task SetupMap()
           {
   
               // Create a portal. If a URI is not specified, www.arcgis.com is used by default.
               ArcGISPortal portal = await ArcGISPortal.CreateAsync();
   
               // Get the portal item for a web map using its unique item id.
               PortalItem mapItem = await PortalItem.CreateAsync(portal, "41281c51f9de45edaf1c8ed44bb10e30");
   
           }
   

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   More info

   ArcGISPortal.CreateAsync() is a static method that returns a new instance of the ArcGISPortal class representing ArcGIS Online. This is the equivalent of:

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   ArcGISPortal portal = await ArcGISPortal.CreateAsync(new Uri("https://www.arcgis.com"));

6. Create a Map using the PortalItem. To display the map, set the MapViewModel.Map property to this new Map.

   MapViewModel.cs

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           private async Task SetupMap()
           {
   
               // Create a portal. If a URI is not specified, www.arcgis.com is used by default.
               ArcGISPortal portal = await ArcGISPortal.CreateAsync();
   
               // Get the portal item for a web map using its unique item id.
               PortalItem mapItem = await PortalItem.CreateAsync(portal, "41281c51f9de45edaf1c8ed44bb10e30");
   
               // Create the map from the item.
               Map map = new Map(mapItem);
   
               // To display the map, set the MapViewModel.Map property, which is bound to the map view.
               this.Map = map;
   
           }
   

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

You should see a map of trails, trailheads and parks 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:

• Display an offline map (on-demand)