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How is dependency injection set up in MAUI? How do you inject a view model into a page? What is the service locator anti-pattern and how do you avoid it in MAUI? How do you register and use HttpClient with IHttpClientFactory in MAUI? How do you resolve services from a static or platform context where constructor injection isn't possible? How do you implement a messaging/event aggregator to decouple view models?
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.NET MAUI › Dependency Injection & Services

What are the DI service lifetimes and when do you use each?

Beginner

Answer

Singleton creates one instance for the app's lifetime—good for shared state, HTTP clients, and caches. Transient creates a new instance per resolution—good for view models and lightweight services. Scoped is per-scope (used more in Blazor Hybrid). Mismatched lifetimes (a singleton depending on a transient) can cause captive dependencies.
builder.Services.AddSingleton<ISettingsService, SettingsService>();
builder.Services.AddTransient<DetailsViewModel>();
Real-world example A settings service is a singleton so all pages read the same values, while each details view model is transient to avoid stale state between visits.

Common follow-ups: What is a captive dependency? | Which lifetime fits a view model?

Dependency Injection MVVM App Lifecycle
All 7 Dependency Injection & Services questions