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Merge branch 'bug-748' of…

…ector into v4.7.x
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dotnetjunkie committed Sep 19, 2019
2 parents 8e5a934 + 1993c3b commit 0251adf89ee984bb47233839c2f96f472a5e1cd4
@@ -9,9 +9,7 @@ namespace SimpleInjector
using System.Linq;
using System.Reflection;
using Microsoft.AspNetCore.Mvc.ApplicationParts;
using Microsoft.AspNetCore.Mvc.Internal;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Razor.Internal;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Razor.TagHelpers;
using Microsoft.Extensions.DependencyInjection;
@@ -76,16 +74,50 @@ public static class SimpleInjectorAspNetCoreBuilderMvcExtensions

var manager = GetApplicationPartManager(builder.Services, nameof(AddTagHelperActivation));

ServiceDescriptor tagHelperDescriptor = GetTagHelperActivatorDescriptor(builder.Services);

builder.Container.RegisterTagHelpers(manager, selector);

builder.Services.AddSingleton<ITagHelperActivator>(p => new SimpleInjectorTagHelperActivator(
new DefaultTagHelperActivator(p.GetRequiredService<ITypeActivatorCache>())));

return builder;

private static ServiceDescriptor GetTagHelperActivatorDescriptor(IServiceCollection services)
var descriptor = FindServiceDescriptor(services, typeof(ITagHelperActivator));

if (descriptor is null)
throw new InvalidOperationException(
$"A registration for the {typeof(ITagHelperActivator).FullName} is missing from the " +
"ASP.NET Core configuration system. This is most likely caused by a missing call to " +
"either services.AddRazorPages(), services.AddControllersWithViews(), " +
"services.AddViewLocalization(), or services.AddRazorViewEngine() as part of the " +
"ConfigureServices(IServiceCollection) method of the Startup class. A call to one of " +
"those methods will ensure the registration of the ITagHelperActivator. The default " +
"ITagHelperActivator registration is used as a fallback.");
else if (descriptor.Lifetime != ServiceLifetime.Singleton)
throw new InvalidOperationException(
$"Although a registration for {typeof(ITagHelperActivator).FullName} exists in the " +
"ASP.NET Core configuration system, the registration is not added as Singleton. " +
$"Instead the registration exists as {descriptor.Lifetime}. This makes it impossible " +
$"Simple Injector's {nameof(AddTagHelperActivation)} method requires the default " +
"ITagHelperActivator to be a Singleton. This is most likely because " +
"ITagHelperActivator was overridden by you or a third-party library. Make sure that " +
"you use one of the AddSingleton overloads to register the default ITagHelperActivator.");
return descriptor;

private static ApplicationPartManager GetApplicationPartManager(
this IServiceCollection services, string methodName)
@@ -170,5 +202,29 @@ private static Registration CreateConcreteRegistration(Container container, Type

return lifestyle.CreateRegistration(concreteType, container);

private static ServiceDescriptor? FindServiceDescriptor(IServiceCollection services, Type serviceType)
// In case there are multiple descriptors for a given type, .NET Core will use the last
// descriptor when one instance is resolved. We will have to get this last one as well.
ServiceDescriptor? descriptor = services.LastOrDefault(d => d.ServiceType == serviceType);

if (descriptor == null && serviceType.GetTypeInfo().IsGenericType)
// In case the registration is made as open-generic type, the previous query will return
// null, and we need to go find the last open generic registration for the service type.
var serviceTypeDefinition = serviceType.GetTypeInfo().GetGenericTypeDefinition();
descriptor = services.LastOrDefault(d => d.ServiceType == serviceTypeDefinition);

return descriptor;

private static object GetInstance(this IServiceProvider provider, ServiceDescriptor descriptor) =>
descriptor.ImplementationInstance != null
? descriptor.ImplementationInstance
: descriptor.ImplementationType != null
? ActivatorUtilities.GetServiceOrCreateInstance(provider, descriptor.ImplementationType)
: descriptor.ImplementationFactory(provider);

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