ASP.NET MVC and ServiceCollection sample

Global.asax.cs

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;
using Microsoft.Extensions.DependencyInjection;
using WebApplication16;
using WebApplication16.Controllers;

[assembly: PreApplicationStartMethod(typeof(MvcApplication), "InitModule")]

namespace WebApplication16
{
    public class MvcApplication : System.Web.HttpApplication
    {
        public static void InitModule()
        {
            RegisterModule(typeof(ServiceScopeModule));
        }

        protected void Application_Start()
        {
            var services = new ServiceCollection();
            ConfigureServices(services);
            ServiceScopeModule.SetServiceProvider(services.BuildServiceProvider());

            AreaRegistration.RegisterAllAreas();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            DependencyResolver.SetResolver(new ServiceProviderDependencyResolver());
        }

        private void ConfigureServices(IServiceCollection services)
        {
            services.AddScoped<ScopedThing>();
            services.AddTransient<HomeController>();
        }
    }

    public class ScopedThing : IDisposable
    {
        public ScopedThing()
        {

        }
        public void Dispose()
        {
        }
    }

    internal class ServiceScopeModule : IHttpModule
    {
        private static ServiceProvider _serviceProvider;

        public void Dispose()
        {

        }

        public void Init(HttpApplication context)
        {
            context.BeginRequest += Context_BeginRequest;
            context.EndRequest += Context_EndRequest;
        }

        private void Context_EndRequest(object sender, EventArgs e)
        {
            var context = ((HttpApplication)sender).Context;
            if (context.Items[typeof(IServiceScope)] is IServiceScope scope)
            {
                scope.Dispose();
            }
        }

        private void Context_BeginRequest(object sender, EventArgs e)
        {
            var context = ((HttpApplication)sender).Context;
            context.Items[typeof(IServiceScope)] = _serviceProvider.CreateScope();
        }

        public static void SetServiceProvider(ServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
        }
    }

    internal class ServiceProviderDependencyResolver : IDependencyResolver
    {
        public object GetService(Type serviceType)
        {
            if (HttpContext.Current?.Items[typeof(IServiceScope)] is IServiceScope scope)
            {
                return scope.ServiceProvider.GetService(serviceType);
            }

            throw new InvalidOperationException("IServiceScope not provided");
        }

        public IEnumerable<object> GetServices(Type serviceType)
        {
            if (HttpContext.Current?.Items[typeof(IServiceScope)] is IServiceScope scope)
            {
                return scope.ServiceProvider.GetServices(serviceType);
            }

            throw new InvalidOperationException("IServiceScope not provided");
        }
    }
}

@davidfowl would this implementation be necessary for services that don't require disposal?

Take this gist for a contrived example with a WebAPI2 project. The scoped service doesn't require disposal, so would that implementation be sufficient or would I be better off implementing something similar to your example in the event that an injected service requires disposal?

Your gist is complexly broken for scoped services. Everything is a singleton.

Ok, thanks! I guess I'm trying to understand the "why" on the way you implemented the scoped service (using ScopedServiceModule and assembly attribute to initialize). Using the Microsoft.Extensions.DependencyInjection package in a .NET Framework 4.6+ project is appealing to me because it would simplify a migration of the app to .NET Core even if just slightly. At the same time I don't want to misuse the functionality due to my lack of knowledge/understanding.

I could use a 3rd party IoC container (Ninject, Autofac, Unity, etc) as I have in the past and they definitely hold your hand to make misuse a little more difficult, but I'd like to use the functionality provided via the Microsoft.Extensions.DependencyInjection package for the reasons I mentioned above.

@aaronmbos Ah! In order to resolve scoped services you need to resolve a service from the scoped container. There should be a DI scope per request and calling GetService on that scope will give you the same instance throughout the request.

Most 3rd party containers do a similar thing, see the Autofac.MVC integration https://github.com/autofac/Autofac.Mvc/blob/c86e656375cd4eec0dfd6aba4a60dd60d44a5789/src/Autofac.Integration.Mvc/RequestLifetimeHttpModule.cs

@davidfowl thanks so much for taking the time to explain that a bit! Super helpful!

Hey @davidfowl , I used your sample code here to build a library that simulates ASP.NET Core's Startup in ASP.NET MVC "classic" and I wanted to get your opinion of it if you'd be willing: https://github.com/arex388/Arex388.AspNet.Mvc.Startup

Thanks!

@arex388 it might be interesting to go further and look at what it means to run the generic host in a classic ASP.NET application as well. That way you get configuration, logging and DI.

@davidfowl this helped tremendously! i inherited a .net app with no structure so i wanted to add a container to it and IServiceCollection is the one i'm the most familiar with. I noticed my scoped dependencies were acting like singletons and after about ten hours of pulling out my hair, i found your gist! thanks!!

Hi @davidfowl
Thanks for your piece of code.
But sometimes, the InvalidOperationException "IServiceScope not provided" is thrown.
It seems to happen after some time of inactivity on our website hosted on IIS.
Have you experienced it ?
We need to restart the website in order to fix the error otherwise, the error is forever raised (on every request)
Best regards,

Are web sockets involved?

No

Is session involved? I'm not sure how inactivity could affect it. Maybe add some logging and see if Begin/End request is firing on the requests that end up failing forever. Do you have a full stack trace? Are you ever trying to resolve things outside of the request? (background task etc).

Here is the stacktrace I get :

[InvalidOperationException: IServiceScope not provided]
   GANet.IoC.ServiceProviderDependencyResolver.GetService(Type serviceType) in C:\AzureDevOpsAgents\artifacts_agent_cluster_2_1\_work\2\s\GA.Net\GANet\IoC\ServiceProviderDependencyResolver.cs:18
   System.Web.Mvc.DependencyResolverExtensions.GetService(IDependencyResolver resolver) +59
   System.Web.Mvc.SingleServiceResolver`1.GetValueFromResolver() +64
   System.Lazy`1.CreateValue() +243
   System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() +32
   System.Lazy`1.get_Value() +14194428
   System.Web.Mvc.SingleServiceResolver`1.get_Current() +19
   System.Web.Mvc.MvcRouteHandler.GetSessionStateBehavior(RequestContext requestContext) +202
   System.Web.Mvc.MvcRouteHandler.GetHttpHandler(RequestContext requestContext) +45
   System.Web.Routing.UrlRoutingModule.PostResolveRequestCache(HttpContextBase context) +219
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +223
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +220
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +94

ligne 18 is where the exception is thrown :

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Mvc;
using Microsoft.Extensions.DependencyInjection;

namespace GANet.IoC
{
    internal class ServiceProviderDependencyResolver : IDependencyResolver
    {
        public object GetService(Type serviceType)
        {
            if (HttpContext.Current?.Items[typeof(IServiceScope)] is IServiceScope scope)
            {
                return scope.ServiceProvider.GetService(serviceType);
            }

            throw new InvalidOperationException("IServiceScope not provided"); <----------------------------------------
        }

        public IEnumerable<object> GetServices(Type serviceType)
        {
            if (HttpContext.Current?.Items[typeof(IServiceScope)] is IServiceScope scope)
            {
                return scope.ServiceProvider.GetServices(serviceType);
            }

            throw new InvalidOperationException("IServiceScope not provided");
        }
    }
}

So no service scope has been added to current HttpContext Items property I guess (or HttpContext.Current is null)

I will add some log to investigate the issue, thank you for your time.

I've found someone that is having a similar problem here : dnnsoftware/Dnn.Platform#4363

My assumption would be that HttpContext.Curent is null? It would be good to figure that out. If there's no service scope it would mean Begin request didn't run, which doesn't seem likely. Definitely do some more debugging to see if HttpContext.Current is null (which is also strange because it look like it's running within the pipeline).