Hi,

I suspect to get the event registry you should be fetching it via dependency injection rather than calling EventRegistry.Instance. If you're in an IInitializableModule, you can do it like this

public class MyInitialisationModule : IInitializableModule
{
    public void Initialize(InitializationEngine context)
    {
        var eventRegistry = context.Locate.Advanced.GetInstance<EPiServer.Events.Clients.IEventRegistry>();
        // Do stuff here
    }

    public void Uninitialize(InitializationEngine context)
    {
        //Add uninitialization logic
    }
}

The documentation is outdated, I will let the CMS Core/Doc team know about it.

Paul's suggestion is the right one, you should be using IEventRegistry instead. 

Thanks for the replies. 

Getting an instance of IEventRegistry from InitializationEngine inside the Initialize method works ok to define what should be done once the event is raised. 

But it is not clear to me, how to get the IEventRegistry in the public method that we call to trigger/raise the event? 
I mean in the RaiseEvent() in the documentation. 

public void RaiseEvent(string message) { 

// without InitializationEngine context, how to get the IEventRegistry here, to raise the event?

}

Without the InitializationEngine there are a few ways. The easiest (though not best) route would be to use ServiceLocator, for example:

var eventRegistry = ServiceLocator.Current.GetInstance<IEventRegistry>();

A better option would be to use constructor injection though that's not available in all situations. For example:

public class MyController : PageController<MyPageType>
{
    private readonly IEventRegistry _eventRegistry;
    public MyController(IEventRegistry eventRegistry)
    {
        _eventRegistry = eventRegistry;
    }

    // Everything else goes here...
}