public RegisterStudentModel Registernumber(RegisterStudentModel registerStudent) { string departmentCode = _departmentGateway.GateDepartmentCodeByDepartmentId(registerStudent.DepartmentId); List <RegisterStudentModel> student = _registerStudentGateway.GateStudentByDepartmentId(registerStudent.DepartmentId); string year = registerStudent.Date.ToString("yyyy"); int yearcount = 0; int count = student.Count; if (count != 0) { foreach (var studentList in student) { string regYear = studentList.Date.ToString("yyyy"); if (regYear == year) { yearcount++; } } } yearcount++; registerStudent.RegistationNumber = departmentCode + "-" + year + "-" + yearcount.ToString().PadLeft(3, '0'); return(registerStudent); }