Autofac asp.net web api constructor injection works but property injection does not - asp.net-web-api

Question

I am beginner in autofac and I have to use it in new legacy project asp.net web api.
I am registering of interface and injection works fine with constructor injection.
However, the constructor is being called in numerous places directly new(), and I don't want to replace it everywhere.
So I thought about property injection, but cannot get it to work, the dependency is always null.
The app is split into multiple projects and multiple autofac modules. Autofac configuration as per docs: https://docs.autofac.org/en/latest/integration/webapi.html
I tried to make small demo app, and I was able to get property injection working using all methods from docs: https://autofac.readthedocs.io/en/latest/register/prop-method-injection.html
using Autofac;
public class Program
{
public static void Main()
{
var builder = new ContainerBuilder();
builder.RegisterType<MyDependency>().As<IMyDependency>().SingleInstance();
builder.RegisterType<MyService>().OnActivated(e => e.Instance.MyDependency1 = e.Context.Resolve<IMyDependency>());
//builder.Register(c => new MyService { MyDependency1 = c.Resolve<IMyDependency>() });
//builder.RegisterType<MyService>().WithProperty("MyDependency1", new MyDependency()).SingleInstance();
var container = builder.Build();
container.Resolve<MyService>();
}
}
public class MyService
{
public IMyDependency MyDependency1 { get; set; }
}
public class MyDependency : IMyDependency
{
public void Hello()
{
Console.WriteLine("Hello from MyDependency1");
}
public MyDependency()
{
Hello();
}
}
public interface IMyDependency
{
public void Hello();
}
Unfortunately none of these works for my full project, the object is always null. I know it would be difficult to get help, but maybe someone can advice what to look for?

Answer 1

I just tried reproducing this using the WithProperty registration you have there and the test passes - I can't reproduce it, property injection is working.
If it's not working in your full project, something else is going on. Below is the totally working test I used to verify.
public class ExampleTests
{
[Fact]
public void PropertyInjection()
{
var builder = new ContainerBuilder();
builder.RegisterType<MyDependency>().As<IMyDependency>().SingleInstance();
builder.RegisterType<MyService>().WithProperty("MyDependency1", new MyDependency()).SingleInstance();
var container = builder.Build();
var svc = container.Resolve<MyService>();
Assert.NotNull(svc.MyDependency1);
}
}
public class MyService
{
public IMyDependency MyDependency1 { get; set; }
}
public class MyDependency : IMyDependency
{
public void Hello()
{
Console.WriteLine("Hello from MyDependency1");
}
public MyDependency()
{
Hello();
}
}
public interface IMyDependency
{
public void Hello();
}