As you can see, the injector class creates an object of the service class, and injects that object to a client object.
In this way, the DI pattern separates the responsibility of creating an object of the service class out of the client class. As you have seen above, the injector class injects the service dependency to the client dependent. The injector class injects dependencies broadly in three ways: through a constructor, through a property, or through a method. Constructor Injection: In the constructor injection, the injector supplies the service dependency through the client class constructor.
Property Injection: In the property injection aka the Setter Injection , the injector supplies the dependency through a public property of the client class. Method Injection: In this type of injection, the client class implements an interface which declares the method s to supply the dependency and the injector uses this interface to supply the dependency to the client class.
Let's take an example from the previous chapter to maintain the continuity. Then, we need to change the source code of the CustomerBusinessLogic class as well. The Dependency injection pattern solves this problem by injecting dependent objects via a constructor, a property, or an interface.
As you see, the CustomerService class becomes the injector class, which sets an object of the service class CustomerDataAccess to the client class CustomerBusinessLogic either through a constructor, a property, or a method to achieve loose coupling.
Let's explore each of these options. As mentioned before, when we provide the dependency through the constructor, this is called a constructor injection. These are example anti-patterns, do not copy the code, do not use these patterns, and avoid these patterns at all costs.
When you register Transient services that implement IDisposable , by default the DI container will hold onto these references, and not Dispose of them until the container is disposed when application stops if they were resolved from the container, or until the scope is disposed if they were resolved from a scope.
This can turn into a memory leak if resolved from container level. In the preceding anti-pattern, 1, ExampleDisposable objects are instantiated and rooted. They will not be disposed of until the serviceProvider instance is disposed. For more information on debugging memory leaks, see Debug a memory leak in. The implementationFactory can be provided as a lambda expression, local function, or method. Result , this will cause a deadlock.
This causes a deadlock. The GetBarAsync method simply emulates an asynchronous work operation with Task. For more information on asynchronous guidance, see Asynchronous programming: Important info and advice. For more information debugging deadlocks, see Debug a deadlock in. When you're running this anti-pattern and the deadlock occurs, you can view the two threads waiting from Visual Studio's Parallel Stacks window.
For more information, see View threads and tasks in the Parallel Stacks window. The term "captive dependency" was coined by Mark Seemann , and refers to the misconfiguration of service lifetimes, where a longer-lived service holds a shorter-lived service captive.
In the preceding code, Foo is registered as a singleton and Bar is scoped - which on the surface seems valid. However, consider the implementation of Foo. The Foo object requires a Bar object, and since Foo is a singleton, and Bar is scoped - this is a misconfiguration.
As is, Foo would only be instantiated once, and it would hold onto Bar for its lifetime, which is longer than the intended scoped lifetime of Bar. When you validate the scopes, you'd get an InvalidOperationException with a message similar to "Cannot consume scoped service 'Bar' from singleton 'Foo'. For more information, see Scope validation.
When using scoped services, if you're not creating a scope or within an existing scope - the service becomes a singleton. DependencyInjection namespace to encapsulate groups of service registrations. Including the namespace portion Microsoft. DependencyInjection for DI extension methods also:. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Tutorial: Use dependency injection in. Please rate your experience Yes No.
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