Dependency Injection in .NET: Service Lifetimes

Choosing the right lifetime for your services is critical for app correctness and memory usage.

Transient

Created every time it is requested. Lightweight, stateless services.

Scoped

Created once per HTTP request. Ideal for DB contexts, user session data. Don’t inject Scoped into Singleton!

Singleton

Created once per application lifetime. Examples: Caching services, configuration. MUST be thread-safe.

services.AddTransient<IEmailSender, EmailSender>();
services.AddScoped<MyDbContext>();
services.AddSingleton<IMemoryCache, MemoryCache>();