If I call GetTransactionList and I use a begin date of December 12th and an end date of December 13th, am I querying transactions by the date they are created or the date they are modified? If a transaction's status changes from authorized to settled, does this query pull that order again?
GetTransactionList use GetSettledBatchList which use settled batch id.
If I call GetUnsettledTransactionList, what dates are used? Am I pulling a list of all unsettled transactions since the beginning of time? Are orders that are unsettled being settled, then being pulled again?
Yes, but it limit to 1000 records.
doc is here
http://developer.authorize.net/downloads/
and you can download the source here
https://github.com/AuthorizeNet/sdk-dotnet
