Now that we have our interfaces ready, our next question is how are we going to register the multiple implementations of a single interface? Change the registrations The built-in support for dependency injection in ASP.NET Core is great. Use Metadata Slight performance overhead when compared to the non-generic method, and when compared Menu This is traditional approach that most of us already may have used very often. Making statements based on opinion; back them up with references or personal experience. This is tricky. The DelegateResolver is the same as before: The next technique uses a wrapper to make each implementation added to the DI container unique, and hence can be retrieved uniquely. Substituting black beans for ground beef in a meat pie. In Unity it's possible to make something like this Rollcall can also be used with a implementation factory, a Func method. This could have big impact on performance and memory if the implementations them themselves have many dependencies (and those dependencies have dependencies and so on). Example may be. Why does sending via a UdpClient cause subsequent receiving to fail? Throughout this post, I'm going to discuss five different ways to pick up a dependency injected from multiple instances sharing with the same interface. Now add the following scoped services to the service collection instance as shown in the next code snippet. AutoFac (which I use in my projects) supports such advanced scenarios. Light bulb as limit, to what is current limited to? Azure Functions leverages the built-in IoC container featured by ASP.NET Core that is easy to use, without having to rely on any third-party libraries. This will ensure that all the implementations of IReminderService will get injected into the controller. Run a GraphQL backend as an Azure Function. Create a Prism application using DryIoC as DI framework. ##3. The logic to retrieve the implementation from IEnumerable is contained in multiple places (each class which has it injected), Retrieval logic is contained in a single place. need to implement the IServiceScope interface, so adding an additional interface requirement would be a big breaking change for those libraries. Depends. But in this particular case, where single interface has multiple implementations, it is not that straight forward. Then this interface should be injected in the controllers. One piece of functionality the .NET DI container does not have (which is available in some other 3rd party DI/IoC containers) is the ability to add and retrieve service implementations by name. Register multiple implementations of an interface and try to resolve all the implementations using container.ResolveMany or container.Resolve< IEnumerable>. In the ConfigureServices method write the following code to add scoped services of each of the ICustomLogger implementations. If you have BMWController that needs concrete car implementation, injecting ICar has no sense - that the magic of DI - you say "gimme implementation of ICar" and don't care what is it. This could be especially problematic if the implementations themselves have a number of dependencies which then need to be instantiated (this was NOT the case with the benchmarks) which could result in a negative performance impact. Not the answer you're looking for? Test the various methods and find which works best and is most optimal for your particular situation. The in built support for Dependency Injection makes life much more simpler as we do not need to deal with static functions; When multiple implementations of an interface are registered, the last one always gets injected; To inject all the registered implementations of the interface, we pass IEnumerable<T> in the constructors. It was a solution I was not very happy with because it meant I had to new up the implementations inside a factory or I had to use service collection to instantiate all implementations of the interface and then use a piece of code to return the one the was . Dependency Injection in ASP.NET Core. Even though some some techniques performed poorly when compared to others, bear in mind that the time frame in question here is nanoseconds (a nanosecond is one billionth of a second). Ensure that the check boxes Enable Docker Support and Configure for HTTPS are unchecked as we wont be using those features here. Concealing One's Identity from the Public When Purchasing a Home. Lets understand this with an example. Injecting and Using Multiple Implementations of a Dependency Once your implementations are registered with the Dependency Injection container, they are ready to be used. In the Create new project window, select ASP.NET Core Web Application from the list of templates displayed. Here is my use case; in my application Im using Serilog. Hence registering services that have a common interface and resolving them at runtime isnt simple. Joydip Kanjilal is a Microsoft MVP in ASP.Net, as well as a speaker and author of several books and articles. Good article. Another possible solution is using a generic type parameter on the interface. One of the features that Serilog has to offer is the concept of an enricher. Now we are back to ConfigureServices method from the beginning of this article where for the same interface we register multiple class types. For more advanced scenarios the users are encouraged to use an IoC of their choice which supports more advanced features (assembly scan, decorators, conditional/parameterized dependencies, etc. It is indeed better to have separate interfaces whenever possible. QGIS - approach for automatically rotating layout window. While building an Azure Functions application, setting an IoC container for dependency injection has many benefits by comparing to just using the static classes and methods. The example I have is based on . An example: The behavior I expected could be achieved using the Assert.All method: As long you are running your Angular application at a root URL (e.g. Member-only .NET6 Dependency Injection One Interface, Multiple Implementations You want to have multiple implementations with the same interface. While building an ASP.NET Core application, setting an IoC container for dependency injection is nearly inevitable. You will have to take a lot of efforts to mock the dependencies. This is shown in Figure 1 below. Redesign your classes However, dealing with multiple implementations of an interface when working with dependency injection in ASP.NET. Everything is clear and consistent with rest of the application. Lets try to discuss three approaches that I can think of right now. When you run this application and the breakpoint is hit, youll observe that all three parameters are instances of type EventLogger because EventLogger has been injected last. Your controller code knows the type name. So o a newer project, I decided to give the built-in IoC container in .NET Core another try. Also, stubbing and mocking is easy. I have used some suggestions provided in StackOverflow question and tried to compile some of my thoughts around those suggestions. Relatively low-level solutions Lamar.Microsoft.DependencyInjection exposes the extension method UseLamar for the IWebHostBuilder, which needs to be called. Short of actually implementing one of these other 3rd party containers, below are a number of different options and techniques one can use to get the correct implementation from the DI container when there are multiple implementations registered. What do you call an episode that is not closely related to the main plot? The next approach is extends on the Factory technique, but only instantiates the requested implementation based on naming conventions. The built-in support for dependency injection in ASP.NET Core is great. Next, declare a shared delegate as shown in the code snippet given below. So dependency injection implementation solved the problem with hard-coded dependency and helped us in making our application flexible and easy to extend. Lets consider a simple problem statement which we will use for the discussion. There can be three types of reminders Email Reminders, SMS Reminders and Push Notifications. Connect and share knowledge within a single location that is structured and easy to search. You can extrapolate from this and apply its own business requirements. spartak varna vs sozopol h2h. Select the API as the template and click OK. Lets say we have three controllers and they need three different implementations of the reminder service: So, we have a single interface and there are three different implementations as shown in the below screenshot. This parameter will update the generated urls for our assets(scripts, css) inside the index.html. I am a Microsoft MVP and currently working as Senior Software Engineer. 2. I usually create separate interfaces for the different implementations (the bonus option). It can has multiple implementations, but you choose only one during registration. So, instead of giving all the power to resolve any type registered in DI, what we can do is we can inject IEnumerable in the constructor as shown below. No hard coded switch statement which needs to be maintained, The most complicated to setup, with the most moving parts, Works with any interface + implementation, and provides all functionality out the box, Slight performance overhead when compared to the non-generic method, Works with any interface + func<>, and provides all functionality out the box. But many applications have been using the dependency injection for injecting every dependency that is needed by each class in the system. He has more than 20 years of experience in IT including more than 16 years in Microsoft .Net and related technologies. java lightweight dependency injection By Nov 3, 2022 . Now I have to make a decision between two implementations and my decided class will set in every constructor that needs an ICar implementation. Let's first discuss when and why you might want to do this. This technique extends the Distinct approach, resolving the limitation of not being able to select or change the implementation at runtime. Other containers like Unity have special attributes, like DependencyAttribute which you can use to annotate the dependency, like. --base-href If you deploy your Angular app to a subfolder, the --base-href is important to generate the correct routes. When a single interface has single implementation, it is easy. I'd prepare a separate interface: Isn't it an overflow of Interfaces if I user something like IBmwCar : ICar for all brands i want to implement? So, you have one interface IEmailReminderService, derived from IReminderService and its corresponding implementation EmailReminderService. How can we now resolve these implementations? 503), Fighting to balance identity and anonymity on the web(3) (Ep. With built-in IoC container, you can only do it via factory method, here with an example on a BmwCarFactory class: The default IoC container is intentionally kept simple to provide basics of dependency injection to get you started and for other IoC containers to be able to easily plugin in there and replace the default implementation. The illustration below will also include example code for using dependency injection in the constructor of your controller class, resolving the service instance, and returning instances of the three classes (FileLogger, DbLogger, and EventLogger) depending on the service type selected at runtime. InfoWorld Every implementation is instantiated (as part of IEnumerable) even if not required or used. Now we are back to ConfigureServices method from the beginning of this article where for the same interface we register multiple class types. Consider the following enum that contains integer constants that correspond to the three types FileLogger, DbLogger, and EventLogger. Otherwise DI don't make sense for me. In our case, as single interface has multiple implementations, we need to use GetServices call, which would return all the registered implementations. These can later be injected as an IEnumerable of that interface. In most scenarios, the DI technique used (if used correctly) is not going to make a massive material different to the performance of the application/service (of course there are exceptions, depending on how complicated the dependency tree is). www.mywebsite.com/angularapp ) these parameters become important. Also added alternative to @JoeAudette's comment using. The number of inspectors should match the number of elements in the list. This is the simplistic solution to resolve any type that we need. The interface prescribes that the implementations provide a method to upload a file ( UploadFile) and a method to get the implementation name ( GetName ). To work with the code examples provided in this article, you should have Visual Studio 2019 installed in your system. Should one Interface have only one implementation? The ideas that I have mentioned here may not be usable as it is, but I am sure this article will provide you some ideas about how can you solve the problem at hand. builder, of type UploaderBuilder: this is an Action which handles keeping track of the name-implementation link. Following these steps should create a new ASP.NET Core MVC project in Visual Studio 2019. Such as when using a generic class and methods with a dependency on another class. What is not possible is to resolve a specific implementation as there is no support for keyed or named services. and want to implement the ICar interface multiple times like, and add the following in the Startup class. There are trade-offs and pros and cons to using each technique - the most performant might be the most difficult to maintain for your situation. Assuming Visual Studio 2019 is installed in your system, follow the steps outlined below to create a new ASP.NET Core MVC project in Visual Studio. container.RegisterType("Female"); The functionality you are looking for isn't easy to implement, at least when you are using it in the controller because controllers are treated a bit specially (By default, controllers aren't registered with ServiceCollection and hence not resolved/instantiated by the container and instead instantiated by ASP.NET Core during the request, see also the explanation and example on my related answer). Use this . This design helps in testing. I blog about C#, .NET and Azure. However this introduces an extra dependency and it comes with a (although short) learning curve. Like previous approach, the disadvantage of this approach is testability. Asking for a collection of all implementations of one interface can be an effective pattern. How does the dependency resolver work and where can i set it up in ASP.NET Core? On most of my projects I'm using Autofac as the Inversion of Control container of my choice. Then Factory Pattern uses a manager class to decide which implementation should be called. Ensure that Authentication is set to No Authentication as we wont be using authentication either. In this article, we are going to see what are various options available for us, if we have one interface, multiple implementations and we use dependency injection container. Please contact the developer of this form processor to improve this message. The factory looks very similar to the handler from the IEnumerable approach: A big negative aspect of the IEnumerable and Factory approach, is that all the implementations are instantiated every time, even if not used or required. ABP's dependency injection infrastructure is built on ASP.NET Core's DI system, automates service registration by conventions and provides some additional features. |. The built in .NET dependency injection (DI) container is all one will need for almost all situations (including this situation): however this scenario can be a bit more challenging to get right - with multiple implementations of the same interface, how do you get the right implementation from the DI container?
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