C# error System.NullReferenceException

Question

I have some problems with System.NullReferenceException. When server do things and we first check user is not null and then he disconnect and server progress something and it tr

Answer 1

Who is setting User to null and where? While your thread sleeps, somebody is obviously setting the User variable to null, causing the crash.

Besides: "Magical sleeps" will not solve any problems. You need proper locking here.