private bool CheckValidity() { if (ClassSeleter.ClassType < 0) { return(RaiseErrOccuredEvent(MessageType.ClassTypeErr)); } if (string.IsNullOrEmpty(ClassSeleter.SelectedClass)) { return(RaiseErrOccuredEvent(MessageType.ClassNameErr)); } if (string.IsNullOrEmpty(ClassSeleter.SelectedTeacher)) { return(RaiseErrOccuredEvent(MessageType.TeacherErr)); } if (ClassCount < 1) { return(RaiseErrOccuredEvent(MessageType.ClassCountErr)); } if (ClassDate.Year < 2000) { return(RaiseErrOccuredEvent(MessageType.ClassDateErr)); } if (!CallingNames.CheckValidity()) { return(RaiseErrOccuredEvent(MessageType.NameCallingNoCallErr)); } return(true); }