title: How to catch DB errors and translate them into meaningful information for the business layer?
body: <p>Usually I have to insert some data in a DB and it can't be inserted because the table has constraints preventing me from doing that. With the app I'm developing, some business rules (like "there are not two persons with the same id type and number" or "the XXXX product is already registered") are enforced with UNIQUE or composite keys and other mechanisms. Although I know that DBMS throws an error message (like ORA-6346 or ) I do not know how to catch those errors in .net 4.0 and translate them to an error that can be meaningful for the business layer.</p>
  
  <p>As an example: I've seen an insertion mechanism that asks the DB if the register already exists and then it proceeds to insert data if it isn't the case. I want to do this only using a query and catching the database constraint violation error because the first way seems to me as very inefficient (DB can alert you about duplication with an error). </p>
  
  <p>How can I implement something like that? </p>
  
  <p>Note: I think that it is possible to catch the exception from the database and use its ORA-xxxx code to try to figure out what has happened. I do not remember with precision if the error message shows which constraint (the name of...) has been broken, but business layer code can contain constants with the constraint names and, from them, know what has happened.</p>