Dependency injection has been a fairly standard part of development for a while. You’ve probably used Unity, Autofac, Ninject and others in the past. <\/p>\n
Frameworks, such as ASP.NET core and MAUI use the Microsoft Dependency Injection package (Microsoft.Extensions.DependencyInjection) and we can use this with any other type of application. <\/p>\n
For example if we create ourselves a Console application, then add the package Microsoft.Extensions.DependencyInjection. Now can then use the following code<\/p>\n
\r\nvar serviceCollection = new ServiceCollection();\r\n\r\n\/\/ add our services\r\n\r\nvar serviceProvider = serviceCollection.BuildServiceProvider();\r\n<\/pre>\nand it’s as simple as that.<\/p>\n
The Microsoft.Extensions.DependencyInjection has most of the features we require for most dependency injection scenarios (Note: it does not support property injection for example). We can add services as…<\/p>\n
\r\nserviceCollection.AddTransient<IPipeline, Pipeline>();\r\n\/\/ or\r\nserviceCollection.AddTransient<Pipeline>();\r\n<\/pre>\n<\/li>\n
\r\nserviceCollection.AddSingleton<IPipeline, Pipeline>();\r\n\/\/ or\r\nserviceCollection.AddSingleton<Pipeline>();\r\n<\/pre>\n<\/li>\n
\r\nserviceCollection.AddScoped<IPipeline, Pipeline>();\r\n\/\/ or\r\nserviceCollection.AddScoped<Pipeline>();\r\n<\/pre>\n<\/li>\n<\/ul>\nFor the services registered as “scoped”, if no scope is created then the code will work more or less like a singleton, i.e. the scope is the whole application, but if we want to mimic ASP.NET (for example) we would create a scope per request and we would do this by using the following<\/p>\n
\r\nusing var scope = serviceProvider.CreateScope();\r\n\r\nvar pipeline1 = scope.ServiceProvider.GetRequiredService<Pipeline>();\r\nvar pipeline2 = scope.ServiceProvider.GetRequiredService<Pipeline>();\r\n<\/pre>\nin the above code the same instance of the Pipeline<\/em> is returned for each GetRequiredService<\/em> call, but when the scope is disposed of or another scope created then a new instance for that scope will be returned.<\/p>\n
The service provider is used to create\/return instances of our services. We can use GetRequiredService<\/em> which will throw and InvalidOperationException if the service is not registered or we might use GetService<\/em> which will not throw an exception but will either return the instance or null.<\/p>\n
Multiple services of the same type<\/strong><\/p>\n
If we register multiple implementations of our services like this<\/p>\n
\r\nserviceCollection.AddTransient<IPipeline, Pipeline1>();\r\nserviceCollection.AddTransient<IPipeline, Pipeline2>();\r\n<\/pre>\nand we use the service provider and use GetRequiredService<IPipeline><\/em> we will get a Pipeline2<\/em> – it will be the the last registered type. <\/p>\n
If we want to get all services registered for type IPipeline then we use GetServices<IPipeline><\/em> and we’ll get an IEnumerable of IPipelines, so if we have a service which take an IPipeline, we’d need to declare it as follows<\/p>\n
\r\npublic class Context(IEnumerable<IPipeline> pipeline)\r\n{\r\n}\r\n<\/pre>\nFinally we have the keyed option, this is allows use to register multiple variations of an interface (for example) and give each a key\/name, for example<\/p>\n
\r\nserviceCollection.AddKeyedTransient<IPipeline, Pipeline1>("one");\r\nserviceCollection.AddKeyedTransient<IPipeline, Pipeline2>("two");\r\n<\/pre>\nNow these will not be returned when using GetServices<IPipeline><\/em> instead it’s expected that we get the service by the key, i.e. <\/p>\n
\r\nvar pipeline = serviceProvider.GetKeyedService<IPipeline>("one");\r\n<\/pre>\nWhen declaring the requirement in our dependent classes we would use the FromKeyedServicesAttribute like this<\/p>\n
\r\npublic class Context([FromKeyedServices("one")] IPipeline pipeline)\r\n{\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"Dependency injection has been a fairly standard part of development for a while. You’ve probably used Unity, Autofac, Ninject and others in the past. Frameworks, such as ASP.NET core and MAUI use the Microsoft Dependency Injection package (Microsoft.Extensions.DependencyInjection) and we can use this with any other type of application. For example if we create ourselves […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[3],"tags":[],"class_list":["post-11091","post","type-post","status-publish","format-standard","hentry","category-c"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts\/11091","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/comments?post=11091"}],"version-history":[{"count":4,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts\/11091\/revisions"}],"predecessor-version":[{"id":11095,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts\/11091\/revisions\/11095"}],"wp:attachment":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/media?parent=11091"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/categories?post=11091"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/tags?post=11091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}