Resolve generic Microsoft.Extensions.Logging.ILogger with Unity - get InvalidCastException


I am trying to register a generic ILogger (from Microsoft.Extensions.Logging, not from Serilog) in Unity (version 4).

I've got the following class:

<pre class="lang-cs prettyprint-override">public class MyClass { private readonly Microsoft.Extensions.Logging.ILogger<MyClass> _logger; public MyClass(Microsoft.Extensions.Logging.ILogger<MyClass> logger) { _logger = logger; } }

And the following Unity registrations and test:

<pre class="lang-cs prettyprint-override">// Arrange IUnityContainer container = new UnityContainer(); // provider from Serilog.Extensions.Logging nuget package var provider = new Serilog.Extensions.Logging.SerilogLoggerProvider(); container.RegisterType(typeof(Microsoft.Extensions.Logging.ILogger<>), new InjectionFactory((ctr, type, name) => { var loggerType = type.GetGenericArguments()[0].FullName; Microsoft.Extensions.Logging.ILogger logger = provider.CreateLogger(loggerType); return logger; })); container.RegisterType<MyClass, MyClass>(); // just for demo purpose. // Assert container.Resolve<MyClass>();

This seems OK to me, too bad I am having the following error when resolving:


Exception is: InvalidCastException - Unable to cast object of type 'Serilog.Extensions.Logging.SerilogLogger' to type 'Microsoft.Extensions.Logging.ILogger`1[MyNamespace.MyClass]'.


How to fix this issue?

Full exception:


Microsoft.Practices.Unity.ResolutionFailedException: Resolution of the dependency failed, type = "MyNamespace.MyClass", name = "(none)". Exception occurred while: Resolving parameter "logger" of constructor MyNamespace.MyClass(Microsoft.Extensions.Logging.ILogger1[[MyNamespace.MyClass, MyNamespace.Infra.UnitTests, Version=, Culture=neutral, PublicKeyToken=edbaf8e9a324553f]] logger). Exception is: InvalidCastException - Unable to cast object of type 'Serilog.Extensions.Logging.SerilogLogger' to type 'Microsoft.Extensions.Logging.ILogger1[MyNamespace.MyClass]'.

</blockquote> <h2>Update</h2>

when using Microsoft.Extensions.DependencyInjection, this works:

<pre class="lang-cs prettyprint-override">// Arrange var serviceCollection = new Microsoft.Extensions.DependencyInjection.ServiceCollection() .AddLogging(builder => builder.AddSerilog()) .AddTransient<MyClass, MyClass>(); var serviceProvider = serviceCollection.BuildServiceProvider(); // Assert serviceProvider.GetService<MyClass>();

So I try to get this working with Unity instead of Microsoft.Extensions.DependencyInjection

Unfortunately there is no AddSerilog for Unity and I'm bound to Unity


The easiest way I have found is to register a factory and reflect their extension method to do it and get the right response type. This example also expects that you have registered an ILoggerFactory.

_container = new UnityContainer(); _container.RegisterInstance<ILoggerFactory>(new LoggerFactory().AddLog4Net(), new ContainerControlledLifetimeManager()); _container.RegisterFactory(typeof(ILogger<>), null, (c, t, n) => { var factory = c.Resolve<ILoggerFactory>(); var genericType = t.GetGenericArguments().First(); var mi = typeof(Microsoft.Extensions.Logging.LoggerFactoryExtensions).GetMethods().Single(m => m.Name == "CreateLogger" && m.IsGenericMethodDefinition); var gi = mi.MakeGenericMethod(t.GetGenericArguments().First()); return gi.Invoke(null, new[] { factory }); });

I resolved this with the help of MakeGenericMethod and a helper method:

<pre class="lang-cs prettyprint-override">private static ILogger<T> CreateLogger<T>(ILoggerFactory factory) { return new Logger<T>(factory); }

And the final code (without reflection caching etc):

<pre class="lang-cs prettyprint-override">// Arrange IUnityContainer container = new UnityContainer(); var logfactory = new LoggerFactory(); var provider = new Serilog.Extensions.Logging.SerilogLoggerProvider(); logfactory.AddProvider(provider); container.RegisterType(typeof(Microsoft.Extensions.Logging.ILogger<>), new InjectionFactory((ctr, type, name) => { var loggerType = type.GetGenericArguments()[0]; var myType = this.GetType(); var createLoggerMethod1 = myType.GetMethod(nameof(CreateLogger),BindingFlags.Static | BindingFlags.NonPublic); var createLoggerMethod = createLoggerMethod1.MakeGenericMethod(loggerType); var logger = createLoggerMethod.Invoke(this, new object[] {logfactory}); return logger; })); container.RegisterType<MyClass, MyClass>(); // Assert container.Resolve<MyClass>();



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