How can I get a reference to the object changed in a PropertyValueChanged event?

When the PropertyValueChanged event is raised, it has an associated PropertyValueChangedEventArgs object. This object has a ChangedItem member that holds the GridItem that was changed.

So if you want to do something with the changed item, your handler could look like:

private void OnPropertyValueChanged(Object sender, PropertyValueChangedEventArgs args) {
    Console.WriteLine($"The changed item was {args.ChangedItem}");
}

This seems to do the job:

e.ChangedItem.GetType().GetProperty("Instance").GetValue(e.ChangedItem)

you could try:

var obj = (sender as propertyGrid1).SelectedObject;