public string Save(ClassRoomAllocation aClassRoom)
 {
     try
     {
         if (aRoomGateway.isexist(aClassRoom))
         {
             return("Please select different Time");
         }
         else if (aRoomGateway.Save(aClassRoom) > 0)
         {
             return("Room Allocated Successfully");
         }
         else
         {
             return("Room Allocation Failed");
         }
     }
     catch (Exception)
     {
         return("Room Allocation Failed");
     }
 }