Maui Dependency Injection

Dependency Injection in .NET MAUI

.NET MAUI uses the same Microsoft.Extensions.DependencyInjection container as ASP.NET Core. All service registration happens in MauiProgram.CreateMauiApp() on builder.Services. The container is built once at startup and is immutable thereafter.

When to Use

• Registering services, ViewModels, and Pages in MauiProgram.cs
• Choosing between AddSingleton, AddTransient, and AddScoped
• Wiring constructor injection for Pages and ViewModels
• Leveraging Shell navigation to auto-resolve DI-registered Pages
• Registering platform-specific service implementations with #if directives
• Designing interfaces for testable service layers

When Not to Use

• XAML data-binding syntax or compiled bindings — use the maui-data-binding skill
• Shell route registration and query parameters — use the maui-shell-navigation skill
• Mocking frameworks or test runners — use standard .NET testing tools (xUnit, NUnit, MSTest) and mocking libraries (NSubstitute, Moq)

Inputs

• A .NET MAUI project with a MauiProgram.cs file
• Knowledge of which services, ViewModels, and Pages need registration
• Target platforms (Android, iOS, Mac Catalyst, Windows) for conditional registrations

Rules That Change the Answer

Do not introduce DI into a project that isn't using it, swap a working service lifetime, or add an interface purely for symmetry — only when the user asked or it fixes a real defect.

Answer narrowly, but completely. When you recommend a lifetime change, show the registration code, and give the realistic alternatives rather than a single verdict — for a unit-of-work or DbContext question that means AddTransient, an explicit IServiceScopeFactory.CreateScope(), and the factory pattern (AddDbContextFactory), with a note on when each fits. A one-line prescription is usually a worse answer than a short menu with trade-offs.

// Explicit scope when you genuinely need unit-of-work semantics
using var scope = scopeFactory.CreateScope();
var db = scope.ServiceProvider.GetRequiredService<MyDbContext>();

Workflow

1. Identify all services, ViewModels, and Pages that need to participate in dependency injection.
2. Choose the correct lifetime for each type — AddSingleton for shared services, AddTransient for Pages and ViewModels.
3. Register all types in MauiProgram.CreateMauiApp() on builder.Services, grouping by category (services, HTTP, ViewModels, Pages).
4. Register Pages as Shell routes in AppShell.xaml.cs so Shell navigation auto-resolves the full dependency graph.
5. Wire each Page to its ViewModel via constructor injection, assigning the ViewModel as BindingContext.
6. Add platform-specific registrations with #if directives, ensuring every target platform is covered or has a fallback.
7. Verify resolution works by running the app and confirming no null dependencies or missing-registration exceptions at runtime.

Lifetime Selection

Key rule: Register Pages and ViewModels as Transient by default. Register shared services as Singleton.

⚠️ Avoid AddScoped unless you manually manage IServiceScope. MAUI has no built-in request scope like ASP.NET Core. MAUI creates one IServiceScope per window, so a Scoped service lives as long as that window; resolved from the root provider it silently behaves as a Singleton. Neither gives per-navigation freshness.

Registration Pattern in MauiProgram.cs

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

    // Services — Singleton for shared state
    builder.Services.AddSingleton<IDataService, DataService>();
    builder.Services.AddSingleton<ISettingsService, SettingsService>();

    // HTTP — use typed or named clients via IHttpClientFactory
    // Requires NuGet: Microsoft.Extensions.Http
    builder.Services.AddHttpClient<IApiClient, ApiClient>();

    // ViewModels — Transient for fresh state per navigation
    builder.Services.AddTransient<MainViewModel>();
    builder.Services.AddTransient<DetailViewModel>();

    // Pages — Transient so constructor injection fires each time
    builder.Services.AddTransient<MainPage>();
    builder.Services.AddTransient<DetailPage>();

    return builder.Build();
}

Constructor Injection

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

public class MainViewModel
{
    private readonly IDataService _dataService;

    public MainViewModel(IDataService dataService)
    {
        _dataService = dataService;
    }

    public async Task LoadAsync() => Items = await _dataService.GetItemsAsync();
}

ViewModel → Page Wiring

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

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