How-To: Register an Endpoint for HTTP Requests

When working with a complex application, centralized registration of your API endpoints is a good practice. This allows you to easily change the endpoint for a given service, and to easily add new services.

Step-by-steps

Important

This guide assumes you used the template wizard or dotnet new unoapp to create your solution. If not, it is recommended that you follow the instructions for creating an application from the template.

1. Enable HTTP

  • Call the UseHttp() method to register a HTTP client with the IHostBuilder which implements IHttpClient:

    protected override void OnLaunched(LaunchActivatedEventArgs args)
{
    var appBuilder = this.CreateBuilder(args)
        .Configure(hostBuilder =>
        {
            hostBuilder.UseHttp();
        });
...

2. Register Endpoints

  • The AddClient extension method is used to register a client with the service collection.

  • While the AddClient() extension method can take a delegate as its argument, the recommended way to configure the HTTP client is to specify a configuration section name. This allows you to configure the added HTTP client using the appsettings.json file.

    protected override void OnLaunched(LaunchActivatedEventArgs args)
{
    var appBuilder = this.CreateBuilder(args)
        .Configure(hostBuilder =>
        {
            hostBuilder.UseHttp(services =>
                services.AddClient<IShowService, ShowService>("ShowService")
            );
        });
...

  • Ultimately, your service will be based on the functionality provided by the web API, but the HttpClient associated with it will be injected into the constructor of your service implementation. You will make requests to the registered endpoint inside your service implementation. In this case, the service interface will look something like this:

    public interface IShowService
{
    Task<Show> GetShowAsync();
}

  • The endpoint is defined in the appsettings.json file. While the default behavior is to use the platform-native HTTP handler, this can be configured.

    {
    "ShowService": {
        "Url": "https://ch9-app.azurewebsites.net/",
        "UseNativeHandler": true
    }
}

3. Use the Service to Request Data

  • Since you registered the service with the service collection, you can now inject the IShowService implementation into your view models and use it to request information about a show from the endpoint:

    public class ShowViewModel : ObservableObject
{
    private readonly IShowService _showService;

    public ShowViewModel(IShowService showService)
    {
        _showService = showService;
    }

    public async Task LoadShowAsync()
    {
        var show = await _showService.GetShowAsync();
...

See also