RE: Using ADO.net in Business Central
Are you running Business Central on-prem or Business Central Online.
If you are running Online you will not have access to the SQL server and have to use an API approach.
If you run BC on prem you can access the SQL database through ADO.net but you should be careful about updating and inserting data because you can not run any business logic through ado.net. But for reading data it works fine.