public List <InvoiceViewModel> FetchInvoicesByAppointmentId(List <Appointment> appointments) { foreach (var appointment in appointments) { Invoice invoice = patientBusinessLayer.GetInvoice(appointment.Id); if (invoice != null) { invoicelist = new InvoiceViewModel(); invoicelist.InvoiceId = invoice.Id; invoicelist.PatientName = patientBusinessLayer.GetPatientNameByAppointmentId(appointment.Id); invoicelist.AppointmentDate = Convert.ToDateTime(patientBusinessLayer.GetAppointmentDate(appointment.Id)); invoicelist.Total = patientBusinessLayer.GetTotalBill(appointment.Id); invoiceListViewModel.Add(invoicelist); } } return(invoiceListViewModel); }