Efficiently identify changed fields in CSV files using c#

Question

This turned out to be more difficult than I thought. Basically, each day a snapshot of a customer master list is being dumped by a system into CSV. It contains about 12000

Answer 1

This may be best accomplished in a database rather than in code: Create two tables, current and old, import the data from the CSV files into the proper tables and use a combination of SQL queries to generate the output.