Autofac interceptor not working for some classes - asp.net-core-2.0

Question

I have to do some extra logic layer on existing classes. I'm using autofac.
The project is Windows service having also Kestrel server. Program.cs e.g.
void Main(string[] args) {
var customQueue = new CustomQueue();
var someClass = new SomeClass(customQueue);
var randomClass = new RandomClass();
// do some logic here with using declared instances
var server = new Server(someClass, randomClass);
server.Start();
}
And here is the Server.cs
class Server {
private IWebHost _host;
public Server(SomeClass cls, RandomClass cls1) {
// set to fields
}
void Start() {
_host = new WebHostBuilder()
.UseKestrel()
.ConfigureServices(services =>
{
services.AddAutoFac(); // first as per doc in order to scaffold 'ConfigureContainer'?
services.AddSingleton(someClass); // fields
services.AddSingleton(randomClass); // fields
})
.UseContentRoot(Directory.GetCurrentDirectory())
.ConfigureAppConfiguration(...)
.ConfigureLogging(...);
.UseStartup<Startuo>()
.Build();
_host.StartAsync();
}
}
Startup.cs
public class Startup
{
public ILifetimeScope AutofacContainer { get; private set; }
public IServiceProvider ConfigureServices(IServiceCollection services)
{
// create a container-builder and register dependencies
var builder = new ContainerBuilder();
// populate the service-descriptors added to `IServiceCollection`
// BEFORE you add things to Autofac so that the Autofac
// registrations can override stuff in the `IServiceCollection`
// as needed
builder.Populate(services);
builder.RegisterType<SomeClass>()
.As<ISomeClass>()
.EnableInterfaceInterceptors()
.InterceptedBy(typeof(SomeClassInterceptor));
builder.Register(_ => new SomeClassInterceptor());
AutofacContainer = builder.Build();
return new AutofacServiceProvider(AutofacContainer);
}
}
And last SomeClassInterceptor.cs
public class SomeClassInterceptor : IInterceptor
{
public void Intercept(IInvocation invocation)
{
try
{
invocation.Proceed();
if (invocation.ReturnValue is Task taskResult)
{
taskResult.ContinueWith(
t =>
{
Console.WriteLine("OOHH YEAHH");
}, TaskContinuationOptions.None);
}
else
{
Console.WriteLine("WOW");
}
}
catch (Exception ex)
{
Console.WriteLine("EXCEPTIOOOOOOOOOOOOONNNNNNNNNNNNNNNNNNNN");
}
}
}
I've tried with Named and Typed registration with having Intercept(...) attribute but still no success. Nothing gets triggered.
Also ISomeClass is inheriting other interfaces, I've tried setting .As<>() also with those but no.
What am I missing?

Answer 1

In order to let the interceptor works. The class should be build by Autofac.
services.AddAutofac();
services.AddSingleton(someClass);
services.AddSingleton(randomClass);
In your case you configure Autofac using the AddAutofac method then add SomeClass as a singleton using the AddSingleton which will override the Autofac configuration. There is no way that Autofac can inject the interceptor in it.
If you want to register SomeClass as singleton you should register it using the SingleInstance() method
builder.RegisterType<SomeClass>()
.As<ISomeClass>()
.SingleInstance()
.EnableInterfaceInterceptors()
.InterceptedBy(typeof(SomeClassInterceptor));