Question

I’m importing a flat file of invoices into a database using C#. I’m using the TransactionScope to roll back the entire operation if a problem is encountered.

It is a tricky input file, in that one row does not necessary equal one record. It also includes linked records. An invoice would have a header line, line items, and then a total line. Some of the invoices will need to be skipped, but I may not know it needs to be skipped until I reach the total line.

One strategy is to store the header, line items, and total line in memory, and save everything once the total line is reached. I’m pursuing that now.

However, I was wondering if it could be done a different way. Creating a “nested” transaction around the invoice, inserting the header row, and line items, then updating the invoice when the total line is reached. This “nested” transaction would roll back if it is determined the invoice needs to be skipped, but the overall transaction would continue.

Is this possible, practical, and how would you set this up?

Answer 1

This is accomplished with a transaction savepoint. It usually looks something like this:

BEGIN TRANSACTION
for each invoice
   SAVE TRANSACTION InvoiceStarted
   BEGIN TRY
     Save header
     Save line 1
     Save line 2
     Save Total
   END TRY
   BEGIN CATCH
     ROLLBACK TO Invoicestarted 
     Log Failed Invoice
   END CATCH
end for
COMMIT

I used a Transact-SQL based pseudo code and this is no accident. Savepoints are a database concept and the .Net Transactions don’t support them. You can use SqlTransaction directly and leverage SqlTransaction.Save or you can use T-SQL stored procedures modeled after an exception safe template. I’d recommend you avoid the .Net transactions (ie. TransactionScope) in this case.