Dependency injection

Version: 10.0

Dependency injection (DI) is a technique for achieving loose coupling between objects and their collaborators, or dependencies. Rather than directly instantiating collaborators, or using static references, the objects a class needs in order to perform its actions are provided to the class in some fashion. Most often, classes will declare their dependencies through their constructor. Sitecore only supports this approach, which is known as constructor injection.

The Sitecore implementation of DI is based on the Microsoft.Extensions.DependencyInjection abstractions from ASP.NET Core.

Service registration

You can register the abstraction either in configuration or with code.

Registration in configuration

You can configure abstraction in the services node in any Sitecore include config file. For example:

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<configuration>
    <sitecore>
        <services>
            <register serviceType="IMyService, MyAbstraction.Assembly" implementationType="MyServiceImplementation, MyImplementation.Assembly" />
            <register serviceType="MyServiceBase, MyAbstraction.Assembly" implementationType="MyServiceBaseImplementation, MyImplementation.Assembly" />
        </services>
    </sitecore>
</configuration>

Registration in code

You use the IServicesConfigurator interface to configure services from code. For example:

Implement the IServicesConfigurator interface:

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public class MyServicesConfigurator : IServicesConfigurator    
    {
        public void Configure(IServiceCollection serviceCollection)
        {
            serviceCollection.AddScoped(typeof(IMyService), typeof(MyServiceImplementation));
            serviceCollection.AddTransient(typeof(MyServiceBase), typeof(MyServiceBaseImplementation));
        }
}

There is more information about IServiceServiceCollection on the MSDN website.

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<configuration>
    <sitecore>
        <services>
            <configurator type= "MyServicesConfigurator, MyAssembly"/>
        </services>
    </sitecore>
</configuration>

Services lifetime

Read important information about Service Lifetimes and Registration Options on the MSDN website.

To support scoped per request lifetime, Sitecore.DependencyInjection.SitecorePerRequestScopeModule, Sitecore.Kernel was added to the http modules. If the module is disabled, Scoped has the same behavior as Singleton.

Service resolution

This section describes how you resolve (locate) a registered service through DI, using a service locator.

Injection to types created by Factory

You must use the resolve attribute. The following changes enable injection for the ShowReason processor of the shutdown pipeline:

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<shutdown>
     <processor type="Sitecore.Pipelines.Shutdown.ShowReason, Sitecore.Kernel" resolve="true"/> </shutdown>

Injection and MVC

By default, Sitecore MVC uses the Sitecore implementation of dependency injection. Configure controllers and their dependencies as described in the current topic, and remember to register both.

Injection to WebForms and UserControls

Use the [Sitecore.DependencyInjection.AllowDependencyInjection] attribute for Forms and UserControls:

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[Sitecore.DependencyInjection.AllowDependencyInjection] 
public partial class Default : System.Web.UI.Page 
{
    protected Default() // important 
    { 
    }
    public Default(IMyService myService, MyServiceBase serviceBase) 
    { 
        … 
    } 
}

The Form must also have a default constructor (this is a limitation of ASP.NET).

Service locator

It is currently not possible to use dependency injection with all parts of Sitecore, so sometimes the service locator is the only solution. This is, for example, the case in page handler factories, MVC controller factories, and in static manager for backward compatibility.

Therefore, you can use the Sitecore.DependencyInjection.ServiceLocator class. For example:

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var service = ServiceLocator.ServiceProvider.GetService(typeof(IMyService))

Or, for example:

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var service = ServiceLocator.ServiceProvider.GetService<MyServiceBase>();

View the dependency injection configuration

You can see the details of the dependency injection at this URL: http://[instance]/sitecore/admin/showservicesconfig.aspx.

You can see configured-in services (node services) at this URL: http://[instance]/sitecore/admin/showconfig.aspx.

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