dependency-injection.md

Using dependency injection increases modularity, testability, maintainability, and improves the design of your application in general. It's even possible to use it for console apps. Use DI whenever possible.

Standard usage

The Delivery SDK offers several methods that extend the IServiceCollection interface. This service enables you to register almost any IoC container available for .NET (including Autofac, Ninject, Castle Windsor, or Unity).

The following sample shows registration to the standard .NET Core container and ASP.NET Core Configuration API.

First, you need to create or extend the appsettings.json file. The properties should match the DeliveryOptions class. Further DeliveryOptions explanation can be found on Delivery options explained.

{
    "DeliveryOptions": {
        "EnvironmentId": "<EnvironmentId_Value>",
        "PreviewApiKey": "<PreviewApiKey_Value>",
        "UsePreviewApi": "true",
        "WaitForLoadingNewContent": "true",
        "DefaultRenditionPreset": "<Default_rendition_preset_codename> so for example value like default, web, mobile ..."
    }
}

To register the IDeliveryClient instance with the configuration, you can use the AddDeliveryClient extension method on the IServiceCollection interface.

public class Startup
{
    public IConfigurationRoot Configuration { get; }

    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<ITypeProvider, CustomTypeProvider>(); // Add an implementation of ITypeProvider generated by https://github.com/kontent-ai/model-generator-net
        services.AddDeliveryClient(Configuration);
    }
}

Now, you can inject a fully configured IDeliveryClient object into your controller:

public class HomeController : Controller
{
    private IDeliveryClient _deliveryClient;

    public HomeController(IDeliveryClient deliveryClient)
    {
        _deliveryClient = deliveryClient;
    }
}

Registering custom implementations of the underlying logic

You can register your custom implementations of the SDK interfaces (such as IContentLinkUrlResolver, ITypeProvider, IRetryPolicyProvider, IDeliveryCacheManager, etc.) through the IServiceCollection interface:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<IContentLinkUrlResolver, CustomContentLinkUrlResolver>();
    services.AddSingleton<IRetryPolicyProvider, CustomPolicyProvider>();
    services.AddDeliveryClient(Configuration);
}

or through the DeliveryClientBuilder class:

IDeliveryClient deliveryClient = DeliveryClientBuilder
                .WithEnvironmentId("<YOUR_ENVIRONMENT_ID>")
                .WithContentLinkUrlResolver(CustomContentLinkUrlResolver)
                .WithRetryPolicyProvider(CustomPolicyProvider>)
                .WithTypeProvider(CustomTypeProvider)
                .Build();

You can also use the DeliveryOptionsBuilder in the AddDeliveryClient method.

services.AddDeliveryClient(builder =>
    builder
        .WithEnvironmentId("<EnvironmentId_Value>")

        // Example production configuration:
        .UseProductionApi("<SecuredApiKey_Value>")
        .WithCustomEndpoint("<ProductionEndpoint_Value>")
        .WithMaxRetryAttempts(3)

        /* Example alternative preview configuration:
        .UsePreviewApi("<PreviewApiKey_Value>")
        .DisableResilienceLogic
        .WithCustomEndpoint("<PreviewEndpoint_Value>")
        */
        .Build()
);

Registering logger

You can register you implementation of the ILoggerFactory through the IServiceCollection interface:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<ILoggerFactory>(LoggerFactoryImplementation);
    services.AddDeliveryClient(Configuration);
}

or through the DeliveryClientBuilder class:

IDeliveryClient deliveryClient = DeliveryClientBuilder
                .WithEnvironmentId("<YOUR_ENVIRONMENT_ID>")
                .WithLoggerFactory(LoggerFactoryImplementation)
                .Build();

By default NullLoggerFactory.Instance implementation is used. If you register LoggerFactory, SDK will have a possibility to provide warning and error messages into your logs.

Currently this is a new option and SDK provides just small amount of logs. For example if you use Caching responses with DistributedCacheManager and FallbackToApi option is chosen for DistributedCacheResilientPolicy parameter of DeliveryCacheOptions, information message will be logged when distributed cache is not available.

Registering multiple clients

In case you need to register multiple differently configured IDeliveryClients, you can take advantage of named clients.

HttpClientFactory

The default implementation of the IDeliveryClient internally uses an HttpClient. We recommend using HttpClientFactory for resolving a HttpClient. You can do so by adding the IDeliveryHttpClient to the HttpClientFactory pipeline.

services.AddHttpClient<IDeliveryHttpClient, DeliveryHttpClient>();

Using the HttpClientFactory increases the stability and performance of your application. It also allows you to set up other features on top of it, such as Polly for Retry Logic.