When you register a service in the DI container, you specify its lifetime. This determines how the DI container creates and manages instances of that service throughout your application’s execution.
Three Main Lifetime Options Transient: Creation: A new instance is created each time the service is requested (injected). Lifetime: The instance lives only as long as it’s needed to fulfill the current request. Usage: Ideal for lightweight, stateless services where each request requires a fresh instance. Example: Database context, logger, helper classes.
Scoped: Creation: A single instance is created per HTTP request (or scope) within your application. Lifetime: The instance is shared throughout the request and disposed of when the request ends. Usage: The most common lifetime for web applications. Ensures consistency within a request while avoiding long-lived objects. Example: User-specific data, transaction handling, shopping carts.
Singleton: Creation: A single instance is created for the entire lifetime of your application. Lifetime: The instance is shared across all requests and components. Usage: Suitable for stateless services, caches, background tasks, or configurations that you want to load once and share globally. Example: Application-wide configuration settings, shared caches, singleton design pattern implementations.
Choosing the Right Lifetime The lifetime you choose for a service depends on its purpose and how you intend to use it: State: If your service holds state that needs to be unique per request, use Scoped. If the state needs to be shared globally, use Singleton. If state is irrelevant, Transient is often sufficient. Resource Usage: Singleton services consume memory for the entire application lifetime, so use them judiciously. Concurrency: Be mindful of concurrency issues when using singleton services in multi-threaded environments.
Lifetime Best Practices Prefer Scoped for Web Apps: In most cases, Scoped is the recommended lifetime for services in web applications. Avoid Captive Dependencies: Don’t inject a shorter-lived service (e.g., Transient) into a longer-lived one (e.g., Singleton). This can lead to unexpected behavior and memory leaks. Consider Thread Safety: If you use a singleton service, ensure it’s thread-safe if it will be accessed concurrently.
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