Unity Container: Method Injection

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Method injection is another form of dependency injection supported by Unity Container. Method injection allows you to inject dependencies into a class through a method call, rather than through a constructor or property.

To use method injection with Unity Container, you can decorate a method with the [InjectionMethod] attribute to indicate that it should be used for injection. You can then register the type with the container and Unity will automatically call the method and inject the dependencies when the type is resolved.

Here is an example of using method injection with Unity Container:

public interface IOrderService
{
    void ProcessOrder(Order order);
}

public class OrderService : IOrderService
{
    private ILogger _logger;

    [InjectionMethod]
    public void Initialize(ILogger logger)
    {
        _logger = logger;
    }

    public void ProcessOrder(Order order)
    {
        _logger.Log("Processing order...");
        // Process the order...
    }
}

container.RegisterType<IOrderService, OrderService>();
container.RegisterType<ILogger, FileLogger>();

var orderService = container.Resolve<IOrderService>();
orderService.ProcessOrder(new Order());

In this example, we are registering the IOrderService and ILogger types with the container. We are decorating the Initialize method in the OrderService class with the [InjectionMethod] attribute to indicate that it should be used for injection.

When we resolve the IOrderService dependency using the container, Unity will automatically call the Initialize method and inject the ILogger dependency into the _logger field. We can then use the ILogger instance in the ProcessOrder method.

Note that you can also specify method parameters in the registration using the InjectionMethod method, similar to the InjectionConstructor method used for constructor injection.

container.RegisterType<IOrderService, OrderService>(
    new InjectionMethod("Initialize", new ResolvedParameter<ILogger>())
);

In summary, Unity Container supports method injection, allowing you to inject dependencies into a class through a method call. This can be useful in cases where you don’t want to inject dependencies through a constructor or property.