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

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.

Steps

Open the 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, get an access token and set the API key.
An API Key gives your app access to secure resources used in this tutorial.
1. Go to the Create an API key tutorial to obtain a new API key access token. Ensure that the following privilege is enabled: Location services > Basemaps > Basemap styles service. Copy the access token as it will be used in the next step.
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
  Use dark colors for code blocks
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { base.OnStartup(e); Esri.ArcGISRuntime.ArcGISRuntimeEnvironment.ApiKey = "YOUR_ACCESS_TOKEN"; } } }
  Warning
  The access token is stored directly in the code as a convenience for this tutorial. Storing access tokens in the source code is not best practice.

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 follow the Model-View-ViewModel (MVVM) design pattern. 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 DisplayAWebMap 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>).

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.

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.
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.

In Visual Studio, in the 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 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;

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);

        }

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()
        {

        }
```
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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.
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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```
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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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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."

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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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"));

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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Use dark colors for code blocks
        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;

        }
Expand

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

If creating apps for Android or iOS, you will need the appropriate emulator, simulator, or device configured for testing (see System requirements for details)

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)