How can I subscribe to an internal static event Action with reflection?

Question

I want to subscribe a delegate to an external class' internal event Action:

internal static event Action OnSingletonReady;

I cannot edit the class it is in. Although the event may be exposed as public in the future, I can't wait for that to happen.

What is necessary to add/remove delegates from an internal action?

Answer 1

I believe that setting the nonPublic argument when you reflect the add method using GetAddMethod would have the desired outcome, at least it did when I tested it.

using System.Reflection;

Console.Title = "Subscribe to Internal Event";
var action = typeof(ReflectionTestClass)
    .GetEvent(nameof(ReflectionTestClass.OnSingletonReady), BindingFlags.Static | BindingFlags.NonPublic);

var methodInfo =
    action?
    .GetAddMethod(nonPublic: true);

    // Subscribe to the action 
    methodInfo?.Invoke(action, new object[] { ()=>
    {        
        Console.WriteLine($@"[{DateTime.Now:hh\:mm\:ss\:fff}] Event received.");
    } } );

Console.WriteLine($@"[{DateTime.Now:hh\:mm\:ss\:fff}]");
await Task.Delay(1000);
_ = ReflectionTestClass.Get();

Console.ReadKey();

class ReflectionTestClass
{
    private ReflectionTestClass() { }
    public static ReflectionTestClass Get()
    {
        if(_singleton is null)
        {
            _singleton = new ReflectionTestClass();
            OnSingletonReady?.Invoke();
        }
        return _singleton;
    }
    private static ReflectionTestClass? _singleton = null;
    internal static event Action? OnSingletonReady;
}