R3 Observable creation on event which requires two arguments.

ObservableFromEventTest.cs

using R3;

var a = new A();
using var x1 = Observable.FromEvent<A.PiyoHandler, int>(h => new A.PiyoHandler(h), h => a.PiyoEvent += h, h => a.PiyoEvent -= h)
    .Subscribe(x => Console.WriteLine($"piyo: {x}"));
using var x2 = Observable.FromEventHandler<int>(h => a.MogeEvent += h, h => a.MogeEvent -= h)
    .Subscribe(x => Console.WriteLine($"moge: {x}"));
using var x3 = Observable.FromEvent<A.HogeHandler, (object?, int)>(h => new A.HogeHandler((sender, arg) => h((sender, arg))), h => a.HogeEvent += h, h => a.HogeEvent -= h)
    .Subscribe(x => Console.WriteLine($"hoge: {x}"));
// See https://aka.ms/new-console-template for more information
a.X(new object(), 1);


class A
{
    public delegate void HogeHandler(object? sender, int arg);
    public delegate void PiyoHandler(int arg);
    public event HogeHandler HogeEvent;
    public event PiyoHandler PiyoEvent;
    public event EventHandler<int> MogeEvent;
    public void X(object? sender, int arg)
    {
        HogeEvent?.Invoke(sender, arg);
        PiyoEvent?.Invoke(arg);
        MogeEvent?.Invoke(sender, arg);
    }
}