Dependency Injection

Avalanche.Service.DependencyInjection.dll adds support to dependency injection.

There are three ways to use dependency injection with Avalanche.Service.IService.

One, is to use Avalanche.Service.IService as a standalone dependency injection implementation.

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

Compability requires support handlers: ServiceRequestHandler, ServiceSelfProvider, ServiceProviderSelfProvider and ServiceScopeHandler.

// Create a list of service descriptors
IServiceCollection serviceCollection = new ServiceCollection()
    .AddSingleton<MyClass>();
// Create service provider
IServiceProvider service = Services.Create(
    (Avalanche.Service.ServiceHandlers.Instance.ServiceRequestHandler,
     Avalanche.Service.ServiceHandlers.Instance.ServiceSelfProvider,
     Avalanche.Service.ServiceHandlers.Instance.ServiceProviderSelfProvider,
     Avalanche.Service.DependencyInjection.ServiceScopeHandler.Instance,
     serviceCollection),
    CachePolicies.Default
);
// Get service
MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;

Two, is adapt IServiceCollection into Avalanche.Service.IService and System.IServiceProvider as dependency injection implementation.

.BuildAvalancheServiceProvider() converts IServiceCollection and IEnumerable<ServiceDescriptor> into handlers, cache policy, entry policy, cancellation tokens, and cancellation token sources.

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

Three, is to use IService as another injectible service in microsoft's DI implementation. .AddAvalancheService() adds IService support. Note that, this way handlers do not automatically participate in construction of services.

// Create service collection
IServiceCollection serviceCollection = new ServiceCollection()
    .AddAvalancheService()
    .AddHandlers(ServiceHandlers.Instance)
    .AddCachePolicy(CachePolicies.Default)
    .AddTransient<MyClass>();
// Create service provider
using var 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;
    }
}

Warning

This dependency injection implementation is experimental.

Full Example

Full example

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

class di_index
{
    public static void Run()
    {
        {
            // <11>
            // Create service descriptor
            ServiceDescriptor serviceDescriptor = ServiceDescriptor.Singleton<MyClass, MyClass>();
            // Create service provider
            IServiceProvider service = Services.Create((ServiceHandlers.Instance, ServiceScopeHandler.Instance, serviceDescriptor), CachePolicies.Default);
            // Get service
            MyClass instance = (MyClass)service.GetService(typeof(MyClass))!;
            // </11>
        }
        {
            // <12>
            // Create a list of service descriptors
            IServiceCollection serviceCollection = new ServiceCollection()
                .AddSingleton<MyClass>();
            // Create service provider
            IServiceProvider service = Services.Create(
                (Avalanche.Service.ServiceHandlers.Instance.ServiceRequestHandler,
                 Avalanche.Service.ServiceHandlers.Instance.ServiceSelfProvider,
                 Avalanche.Service.ServiceHandlers.Instance.ServiceProviderSelfProvider,
                 Avalanche.Service.DependencyInjection.ServiceScopeHandler.Instance,
                 serviceCollection),
                CachePolicies.Default
            );
            // 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 var 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 var 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>
}