BaseType of a Basetype

sim is MainSim;
(sim as MainSim) != null;
sim.GetType().IsSubclassOf(typeof(MainSim));
typeof(MainSim).IsAssignableFrom(sim.GetType());

sim is MainSim;
(sim as MainSim) != null;
sim.GetType().IsSubclassOf(typeof(MainSim));
typeof(MainSim).IsAssignableFrom(sim.GetType());

bool IsMainSimType(Type t)
 { if (t == typeof(MainSim)) return true;
   if (t == typeof(object) ) return false;
   return IsMainSimType(t.BaseType);
 }

if (sim is MainSim)

return t is MainSim;