How to implement / register singleton HttClientFactory in Xamarin Forms

Question

I am using Xamarin Forms with Prism.

How can I register a service for HttpClientFactory? Is there a equivalent in xamarin/prism to the ConfigureServices method in .net core?

I would like to use the equivalent of this code in Xamarin forms:

    services.AddHttpClient<MyClient>("MyHttpClient",
        x => { x.BaseAddress = new Uri("example.com"); }
        ).AddPolicyHandler(GetRetryPolicy());
    services.AddSingleton<MyClientFactory>();

I have been trying different ways and I cannot find the right way to do it.

Thanks a lot.

UPDATE

I have got these clases in a netstandard ClassLibrary called BusinessLogic

MyClientFactory.cs:

namespace BusinessLogic.Services
{
    public class MyClientFactory
    {
        private readonly IServiceProvider _serviceProvider;

        public MyClientFactory(IServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
        }

        public MyClient Create()
        {
            return _serviceProvider.GetRequiredService<MyClient>();
        }
    }
}

MyClient.cs:

namespace ServiceBusinessLogic.Services
{
    public class MyClient : IMyClient
    {
        private readonly HttpClient _httpClient;
        private readonly ILogger<MyClient> _logger;

        public MyClient(ILogger<MyClient> logger, HttpClient httpClient)
        {
            _logger = logger;
            _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
        }

        public async Task<Result<Token>> GetToken(CancellationToken cancellationToken, string userName, string password)
        {
            try
            {
                HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, "Token");
                request.Content = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair<string, string>("grant_type", "password"),
                    new KeyValuePair<string, string>("username", userName),
                    new KeyValuePair<string, string>("password", password)
                });

                HttpResponseMessage result = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
                if (!result.IsSuccessStatusCode)
                {
                    _logger.LogError("the status code is: {0}", (int)result.StatusCode);

// CODE abbreviated for reading

        }

Interface IMyClient.cs:

namespace MyBusinessLogic.Services
{
    public interface IMyClient
    {
        Task<Result<Token>> GetToken(CancellationToken cancellationToken, string userName, string password);
    // CODE abbreviated for reading

MyClientQueries.cs:

namespace MyBusinessLogic.Services
{
    public class MyClientQueries
    {
        private readonly MyClientFactory _myClientFactory;

        public MyClientQueries(MyClientFactory myClientFactory)
        {
            _MyClientFactory = myClientFactory ?? throw new ArgumentNullException(nameof(myClientFactory));

        }

        public async Task<Result<Token>> GetToken(CancellationToken cancellationToken, string username, string password)
        {
            var mysClient = _myClientFactory.Create();
            var response = await tsClient.GetToken(cancellationToken, username, password).ConfigureAwait(true);

            return response;
        }
// CODE abbreviated

Then I have got a xamarin forms Project with Prism called App_Mobile_test

App.xaml.cs:

 public partial class App : PrismApplication
    {
         public App() : this(null) { }

        public App(IPlatformInitializer initializer) : base(initializer) { }

        protected override async void OnInitialized()
        {
            InitializeComponent();

            await NavigationService.NavigateAsync("NavigationPage/MainPage");
        }

        protected override void RegisterTypes(IContainerRegistry containerRegistry)
        {
            containerRegistry.RegisterForNavigation<NavigationPage>();
            containerRegistry.RegisterForNavigation<MainPage>();

        }
    }

I would like to use MyClientQueries which uses DI for HttpClientFactory and HttpClient in the Xamarin Forms project as a service (singleton) so I can call GetToken and all the other methods that are in that class.

But I do not know how to do this in Xamarin Forms.

MyBusinessProject that contains MyClientQueries which I want to use, is already used in a asp.net core mvc and the services were added in the startup.cs in .net core like this:

public void ConfigureServices(IServiceCollection services)
{
#region "api service"  

            services.AddSingleton<MyClientQueries>();

            services.AddHttpClient<MyClient>("MyHttpClient", 
                x => { x.BaseAddress = new Uri(Configuration["APIConfiguration:BaseAddress"]); }
                ).AddPolicyHandler(GetRetryPolicy());

            services.AddSingleton<MyClientFactory>();

            #endregion
//CODE abbreviated
}

How can I register the same objects I am doing in the .net Core app, but in Xamarin Forms and use the dependency injection for the view models? The shared project "MyBusinessLogic" works fine in the asp.net core, and I would like to reuse this project in the Xamarin project. Specially MyClientQueries which has got HttpClientFactory dependency.

Answer 1

It will depend on what DI you are using as to what the syntax will be, but generally that sort of code will be in the App constructor or a method called by the constructor.

So for example you might have a method called RegisterServices in your App.xaml.cs that is called from the constructor, after the Xamarin Init() has been called.

Inside that RegisterServices Method you would have something like this:

   FreshIOC.Container.Register<IHttpManager, HttpManager>().AsSingleton();

We use FreshMvvm which uses TinyIOC for Dependancy Injection, so the syntax may differ, but the concept will be the same.