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.
PrerequisitesBefore 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.
Develop or downloadYou have two options for completing this tutorial:
Option 1: Develop the codeTo 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 solutionThe 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.
Rename the namespace used by classes in the project.
MapViewModel class, double-click the namespace name (DisplayAMap) to select it, and then right-click and choose Rename....Build the project.
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.
41281c51f9de45edaf1c8ed44bb10e30
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.
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;
}
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()
{
}
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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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();
}
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");
}
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;
}
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 will 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.
Alternatively, you can download the tutorial solution, as follows.
Option 2: Download the solutionClick the Download solution link in the right-hand panel of the page.
Unzip the file to a location on your machine.
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 authenticationTo 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.
You can implement API key authentication or user authentication in this tutorial. Compare the differences below:
API key authentication
Learn more in API key authentication.
User authentication
Learn more in User authentication.
Security and authentication guideTo learn more about the different types of authentication, visit Types of authentication.
Create a new API key access token with privileges to access the secure resources used in this tutorial.
Complete the Create an API key tutorial and create an API key with the following privilege(s):
Copy and paste the API key access token into a safe location. It will be used in a later step.
Create new OAuth credentials to access the secure resources used in this tutorial.
WarningConfiguration steps later in the tutorial will assume that your redirect URL is my-app://auth. If you use a different URL, make sure to configure your app's settings accordingly.
Complete the Create OAuth credentials for user authentication tutorial to obtain a Client ID and Redirect URL.
A Client ID uniquely identifies your app on the authenticating server. If the server cannot find an app with the provided Client ID, it will not proceed with authentication.
The Redirect URL (also referred to as a callback url) is used to identify a response from the authenticating server when the system returns control back to your app after an OAuth login. Since it does not necessarily represent a valid endpoint that a user could navigate to, the redirect URL can use a custom scheme, such as my-app://auth. It is important to make sure the redirect URL used in your app's code matches a redirect URL configured on the authenticating server.
Copy and paste the Client ID and Redirect URL into a safe location. They will be used in a later step.
All users that access this application need account privileges to access the ArcGIS Basemap Styles service.
Set developer credentials in the solutionTo 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.
In Visual Studio, in the Solution Explorer, click App.xaml.cs to open the file.
Set the ArcGISEnvironment.ApiKey property with your API key access token.
App.xaml.cs
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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();
}
Remove the code that sets up user authentication.
App.xaml.cs
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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.
From the Visual Studio Solution explorer window, open the ArcGISLoginPrompt.cs file.
Set your values for the client ID (OAuthClientID) and the redirect URL (OAuthRedirectUrl). These are the user authentication settings you created in the Set up authentication step.
ArcGISLoginPrompt.cs
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internal static class ArcGISLoginPrompt
{
private const string ArcGISOnlineUrl = "https://www.arcgis.com/sharing/rest";
// Specify the Client ID and Redirect URL to use with OAuth authentication.
// See the instructions here for creating OAuth app settings:
// https://developers.arcgis.com/documentation/security-and-authentication/user-authentication/tutorials/create-oauth-credentials-user-auth/
private const string AppClientId = "YOUR_CLIENT_ID";
private const string OAuthRedirectUrl = "YOUR_REDIRECT_URL";
In Visual Studio, in the Solution Explorer, click App.xaml.cs to open the file.
Remove the line of code that sets an API key access token.
App.xaml.cs
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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 OAuth credentials are 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 solutionClick 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 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:
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