Integrating MEF with DependencyInjection

gistfile1.txt

// Taken from https://weblogs.asp.net/ricardoperes/integrating-managed-extensibility-framework-with-the-net-service-provider
// Other interesting links:
// https://weblogs.asp.net/ricardoperes/dynamically-loading-middleware-in-asp-net-core
// https://weblogs.asp.net/ricardoperes/using-mef-in-net-core

public static class ContainerConfigurationExtensions
{
	public static ContainerConfiguration WithAssembliesInPath(this ContainerConfiguration configuration, string path, SearchOption searchOption = SearchOption.TopDirectoryOnly)
	{
		return WithAssembliesInPath(configuration, path, null, searchOption);
	}

	public static ContainerConfiguration WithAssembliesInPath(this ContainerConfiguration configuration, string path, AttributedModelProvider conventions, SearchOption searchOption = SearchOption.TopDirectoryOnly)
	{
		var assemblyFiles = Directory.GetFiles(path, "*.dll", searchOption);
		var assemblies = assemblyFiles.Select(AssemblyLoadContext.Default.LoadFromAssemblyPath);
		configuration = configuration.WithAssemblies(assemblies, conventions);
		return configuration;
	}
}

public static class ServiceCollectionExtensions
{
	public static IServiceCollection AddFromAssembliesInPath<T>(this IServiceCollection services, ServiceLifetime lifetime, string path = null)where T : class
	{
		var factory = new ExportFactory<T, object>(() => new Tuple<T, Action>(Activator.CreateInstance<T>(), () =>
		{
		}

		), new object ());
		var conventions = new ConventionBuilder();
		var builder = conventions.ForTypesDerivedFrom<T>().Export<T>();
		if (lifetime == ServiceLifetime.Singleton)
		{
			builder = builder.Shared();
		}

		path = path ?? AppContext.BaseDirectory;
		var configuration = new ContainerConfiguration().WithAssembliesInPath(path, conventions);
		using (var container = configuration.CreateContainer())
		{
			var svcs = container.GetExports<Lazy<T>>();
			foreach (var svc in svcs)
			{
				services.Add(new ServiceDescriptor(typeof (T), sp => svc.Value, lifetime));
			}
		}

		return services;
	}

	public static IServiceCollection AddSingletonFromAssembliesInPath<T>(this IServiceCollection services, string path = null)where T : class
	{
		return AddFromAssembliesInPath<T>(services, ServiceLifetime.Singleton, path);
	}

	public static IServiceCollection AddScopedFromAssembliesInPath<T>(this IServiceCollection services, string path = null)where T : class
	{
		return AddFromAssembliesInPath<T>(services, ServiceLifetime.Scoped, path);
	}

	public static IServiceCollection AddTransientFromAssembliesInPath<T>(this IServiceCollection services, string path = null)where T : class
	{
		return AddFromAssembliesInPath<T>(services, ServiceLifetime.Transient, path);
	}
}