Transaction Responsibility

The last post on transactions explained the need to open a transaction of our own before trying to modify a document during an event. That is actually not all. We also need to remember that starting a transaction is not permitted at all times, and also that starting a new transaction or ending one may fail. This leaves us with a certain amount of responsibility. Therefore, we should add some error handling to ensure that failures are handled gracefully. The sample should be amended like this:

void application_OnDocumentNewed( Document doc )
{
  // we cannot modify the document 
  // unless a transaction is started
 
  if( doc.BeginTransaction() )
  {
    // once a new transaction is started
    // we are responsible for ending or 
    // aborting it, so we have to put 
    // everything in a try-catch block
 
    try
    {
      CreateUserDefinedParameters( doc );
 
      // we are responsible for ending 
      // the transaction we started
 
      doc.EndTransaction();
    }
    catch( Exception )
    {
      // if we cannot finish what we wanted
      // we should probably abort the whole thing
 
      doc.AbortTransaction();
      throw; // re-throw the exception
    }
  }
}

Thank you to Arnost Lobel and Harry Mattison for providing this feedback!

I have arrived in Perugia by now … rather slow progress, but getting there.