public IList <InvoiceViewModel> GetByCompanyId(string companyId)
 {
     return(_invoiceRepository.GetByCompanyId(companyId)
            .Select(i => new InvoiceViewModel()
     {
         InvoiceId = i.InvoiceId,
         BillingContactName = i.BillingContactName,
         GrandTotal = i.GrandTotal,
     }).ToList <InvoiceViewModel>());
 }