That’s because a cast can not be used to gain a reference. It transforms a reference from a child or parent class into the desired one.
This is exactly what I meant when I speculated that you may misunderstand how casting works. A cast does not help you in this scenario. You can not pull a reference from thin air.
Now that we have established that, may I ask what exactly you have and what exactly you are trying to do? Because I’m certain it is possible somehow but I’d have to guess a lot of side factors that would make any suggestions I might provide wrong, almost guaranteed.