Скачать или смотреть How to Make Controllers Scoped or Singleton Instead of Transient in ASP.NET Core

Learn how to change the lifetime of your ASP.NET Core controllers from the default transient to scoped or singleton, allowing for greater control over controller instances and improved dependency management.
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Understanding Controller Lifetimes in ASP.NET Core

In the world of ASP.NET Core development, dependency injection (DI) plays a crucial role in managing the lifetime of services, including controllers. By default, controllers are registered with a transient lifetime, meaning that a new instance is created every time one is requested. This can lead to unnecessary resource use, especially in applications with a high volume of requests.

But what if you want to change the lifetime of your controllers? Maybe you need them scoped (one instance per request) or singleton (only one instance for the entire application)? In this guide, I'll guide you through how to achieve this effectively, giving you better control over your ASP.NET Core application's architecture.

The Default Behavior of Controller Registration

Before diving into the solution, it’s important to note that ASP.NET Core’s controllers are not registered at all by default. Instead, a built-in service called IControllerActivator dynamically creates controller instances without explicit registration. This means that if you want to change their lifecycle behavior, you must modify the DI container’s setup.

The Simple Fix: Adding Controllers as Services

To allow for more control over the lifecycle of your controllers, you can modify your services configuration. Here’s the base command that you can use in your Startup.cs file to register controllers as services:

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Implementing the above line replaces the default IControllerActivator with a ServiceBasedControllerActivator, ensuring controllers are now invoked from the DI container. However, there's a catch: this method always uses the transient lifestyle for controllers, and there is no way to modify that behavior directly.

Customizing the Registration for Scoped or Singleton Lifetimes

If you wish to register your controllers with different lifetimes, you'll need to create your own implementation of AddControllersAsServices. Below is a custom method that allows you to specify the desired service lifetime:

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Using the Custom Extension Method

Now that you have your custom method, you can easily register controllers as either scoped or singleton. Here’s how you can call the new feature from your Startup.cs:

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This flexibility allows you to optimize resource management in your ASP.NET Core applications based on your specific needs.

Important Considerations

A Word of Caution: Singleton Controllers

While using singleton services might seem beneficial for performance, be cautious! If your controllers derive from Controller or ControllerBase, they inherently contain state information. Registering these classes as singleton can lead to unexpected behavior due to shared state among requests. Always evaluate your use case carefully before resorting to Singleton registrations.

Conclusion

Changing the lifetime of your controllers in ASP.NET Core can significantly enhance your application's efficiency and dependency management. By following the steps outlined in this post, you can transition from the default transient lifetime to either scoped or singleton as needed. This not only aids in resource optimization but also improves overall application performance. Happy coding!