Improve error checking on voucher downloads.

BulkPrintingAPI/Controllers/Utils.cs

                 voucherStream.Position = 0;
                 using (var streamReader = new StreamReader(voucherStream))
                 {
+                    int voucherCount = 0;
                     while (streamReader.Peek() >= 0)
                     {
                         var line = streamReader.ReadLine();
                         var parts = line.Split('|');
 
-                        VoucherSanityCheck(batch, decimal.Parse(parts[4]), int.Parse(parts[5]),
-                            parts[7]);
+                        VoucherSanityCheck(batch, decimal.Parse(parts[4]), int.Parse(parts[5]), parts[7]);
+
+                        // Duplicate sequence numbers are taken care of by the unique index on the vouchers table.
+                        int sequenceNumber = int.Parse(parts[6]);
+                        if ((sequenceNumber < 1) || (sequenceNumber > batch.DeliveredQuantity))
+                        {
+                            throw new Exception(String.Format("Voucher sequence number out of range in batch {0}: {1}",
+                                batch.Id, sequenceNumber));
+                        }
 
                         context.Add(new Voucher()
                         {
                             ExpiryDate = DateTime.Parse(parts[1]),
                             Serial = parts[2],
                             EncryptedPIN = parts[3],
-                            SequenceNumber = int.Parse(parts[6]),
+                            SequenceNumber = sequenceNumber,
                             Batch = batch
                         });
+                        voucherCount++;
+                    }
+
+                    if (voucherCount != batch.DeliveredQuantity)
+                    {
+                        throw new Exception(String.Format("Voucher count mismatch for batch {0}: expected={1}, got={2}",
+                            batch.Id, batch.DeliveredQuantity, voucherCount));
                     }
                 }