/maui-dependency-injection

Dependency Injection API Reference

Service Registration in MauiProgram.cs

Register services on builder.Services inside CreateMauiApp():

public static MauiApp CreateMauiApp()
{
    var builder = MauiApp.CreateBuilder();
    builder.UseMauiApp<App>();

    // Services
    builder.Services.AddSingleton<IDataService, DataService>();
    builder.Services.AddTransient<IApiClient, ApiClient>();

    // ViewModels
    builder.Services.AddTransient<MainViewModel>();
    builder.Services.AddTransient<DetailViewModel>();

    // Pages
    builder.Services.AddTransient<MainPage>();
    builder.Services.AddTransient<DetailPage>();

    return builder.Build();
}

Lifetime Reference

Constructor Injection

Inject dependencies through the constructor. The DI container resolves them automatically when the type is itself resolved from the container:

public class MainViewModel
{
    private readonly IDataService _dataService;
    private readonly IApiClient _apiClient;

    public MainViewModel(IDataService dataService, IApiClient apiClient)
    {
        _dataService = dataService;
        _apiClient = apiClient;
    }
}

ViewModel → Page Pattern

Register both the ViewModel and the Page. Inject the ViewModel into the Page constructor and assign it as BindingContext:

public partial class MainPage : ContentPage
{
    public MainPage(MainViewModel viewModel)
    {
        InitializeComponent();
        BindingContext = viewModel;
    }
}

Automatic Resolution via Shell Navigation

When Pages are registered in the DI container and registered as Shell routes, Shell resolves them (and their dependencies) automatically:

// In MauiProgram.cs
builder.Services.AddTransient<DetailPage>();
builder.Services.AddTransient<DetailViewModel>();

// Route registration (AppShell.xaml.cs or startup)
Routing.RegisterRoute(nameof(DetailPage), typeof(DetailPage));

// Navigation — DI resolves DetailPage and its DetailViewModel
await Shell.Current.GoToAsync(nameof(DetailPage));

Explicit Resolution

When constructor injection is not available, resolve services explicitly:

// From any Element with a Handler
var service = this.Handler.MauiContext.Services.GetService<IDataService>();

IServiceProvider Injection

Inject IServiceProvider when you need to resolve services dynamically:

public class MyService
{
    private readonly IServiceProvider _serviceProvider;

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

    public void DoWork()
    {
        var api = _serviceProvider.GetRequiredService<IApiClient>();
    }
}

Platform-Specific Service Registration

Use preprocessor directives to register platform-specific implementations:

// In MauiProgram.cs
#if ANDROID
builder.Services.AddSingleton<INotificationService, AndroidNotificationService>();
#elif IOS || MACCATALYST
builder.Services.AddSingleton<INotificationService, AppleNotificationService>();
#elif WINDOWS
builder.Services.AddSingleton<INotificationService, WindowsNotificationService>();
#endif

Interface-First Pattern for Testability

Define interfaces for services so implementations can be swapped in tests:

public interface IDataService
{
    Task<List<Item>> GetItemsAsync();
}

public class DataService : IDataService
{
    public async Task<List<Item>> GetItemsAsync() { /* ... */ }
}

// Register the interface → implementation mapping
builder.Services.AddSingleton<IDataService, DataService>();

In tests, substitute a mock without touching production code:

var services = new ServiceCollection();
services.AddSingleton<IDataService, FakeDataService>();