public bool IsPaid()
 {
     if (VendorPayments != null && VendorPayments.Count > 0)
     {
         var paymentSum = VendorPayments.Sum(p => p.Amount);
         if (paymentSum == PurchaseInvoiceLines.Sum(l => l.Amount * l.Quantity))
         {
             return(true);
         }
     }
     return(false);
 }
 public bool IsPaid()
 {
     return(PurchaseInvoiceLines.Sum(a => a.Amount) == VendorPayments.Sum(a => a.Amount));
 }