Dependency Injection

Avalanche.Service.DependencyInjection.dll adds glue-on support for dependency injection.

There are three ways how dependency injection can be used with Avalanche.Service.

One, is to adapt ServiceDescriptions into handlers and use Avalanche.Service as Avalanche.Service.IService and thus System.IServiceProvider (Avalanche.Service.IService extends System.IServiceProvider).

// Create service descriptor
ServiceDescriptor serviceDescriptor = ServiceDescriptor.Singleton<MyClass, MyClass>();
// Create service provider
IService service = Services.Create((ServiceHandlers.Instance, ServiceScopeHandler.Instance, serviceDescriptor));
// Get service
MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;

On Asp.Net see instructions.

Two, is to build from IServiceCollection into Avalanche.Service as DI implementation (instead of Microsoft's DI implementation).

.BuildAvalancheServiceProvider() builds IService (and IServiceProvider).

// Create service collection
IServiceCollection serviceCollection = new ServiceCollection()
    .AddHandlers(ServiceHandlers.Instance)
    .AddCachePolicy(CachePolicies.Default)
    .AddTransient<MyClass>();
// Create service
using IServiceDisposable service = serviceCollection.BuildAvalancheServiceProvider();
// Get service
MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;

Three, is to use Avalanche.Service.IService as another injectible service in microsoft's DI implementation. .AddAvalancheService() adds ServiceDescriptions for IService. Note that, this way handlers cannot participate in construction of services described with ServiceDescription.

// Create service collection
IServiceCollection serviceCollection = new ServiceCollection()
    .AddAvalancheService()
    .AddHandlers(ServiceHandlers.Instance)
    .AddCachePolicy(CachePolicies.Default)
    .AddTransient<MyClass>();
// Create service provider
using ServiceProvider service = serviceCollection.BuildServiceProvider();
// Get service
MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;

IService gets injected.

public class MyClass
{
    IService service;

    public MyClass(IService service)
    {
        this.service = service;
    }
}

Note

If there is discrepancy between Microsoft's and Avalanche dependency injection implementation, please report it to github issue tracking.

Full Example

Full example

using System;
using Avalanche.Service;
using Microsoft.Extensions.DependencyInjection;

class di_index
{
    public static void Run()
    {
        {
            // <11>
            // Create service descriptor
            ServiceDescriptor serviceDescriptor = ServiceDescriptor.Singleton<MyClass, MyClass>();
            // Create service provider
            IService service = Services.Create((ServiceHandlers.Instance, ServiceScopeHandler.Instance, serviceDescriptor));
            // Get service
            MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;
            // </11>
        }
        // The minimum set of handlers is: <b>ServiceRequestHandler</b>, <b>ServiceSelfProvider</b>, <b>ServiceProviderSelfProvider</b> and <b>ServiceScopeHandler</b>.
        {
            // <12>
            // Create a list of service descriptors
            IServiceCollection serviceCollection = new ServiceCollection()
                .AddSingleton<MyClass>();
            // Create service provider
            IService service = Services.Create(
                (ServiceHandlers.Instance.ServiceRequestHandler,       // Avalanche.Service.dll
                 ServiceHandlers.Instance.ServiceSelfProvider,         // Avalanche.Service.dll
                 ServiceHandlers.Instance.ServiceProviderSelfProvider, // Avalanche.Service.dll
                 ServiceScopeHandler.Instance,                         // Avalanche.Service.DependencyInjection.dll
                 serviceCollection)
            );
            // Get service
            MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;
            // </12>
        }

        {
            // <21>
            // Create service collection
            IServiceCollection serviceCollection = new ServiceCollection()
                .AddHandlers(ServiceHandlers.Instance)
                .AddCachePolicy(CachePolicies.Default)
                .AddTransient<MyClass>();
            // Create service
            using IServiceDisposable service = serviceCollection.BuildAvalancheServiceProvider();
            // Get service
            MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;
            // </21>
        }

        {
            // <31>
            // Create service collection
            IServiceCollection serviceCollection = new ServiceCollection()
                .AddAvalancheService()
                .AddHandlers(ServiceHandlers.Instance)
                .AddCachePolicy(CachePolicies.Default)
                .AddTransient<MyClass>();
            // Create service provider
            using ServiceProvider service = serviceCollection.BuildServiceProvider();
            // Get service
            MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;
            // </31>
        }
    }

    // <MyClass>
    public class MyClass
    {
        IService service;

        public MyClass(IService service)
        {
            this.service = service;
        }
    }
    // </MyClass>
}