When should I be using Odbc, OleDb, SQLClient? What are the trade-offs

Question

I am starting off with a SQLServer database. So it would seem that I should use System.Data.SqlClient namespace. But, there is a chance that we might shut down our SqlServer database and go to MySql or Oracle. For this reason, I am coming up with a set of standards on how our .Net apps will communicate with the database, so as to make it easier to migrate to a different database system in the future if we needed to do so.

So here are the standards:

1. Use an ORM if possible (eg NHibernate) (No LINQ as it only supports SqlServer, but what about Entity framework and its support for Oracle and MySql?)
2. If ORM is an over-kill, then use parameterized SQL queries.
3. Use stored procedures only for long running or complex actions that need to be performed on the database.

Which brings me to my main question at hand. Which namespace should I be using to code my DAL?

It looks to me that the choice is between System.Data.ODBC and System.Data.OleDB:

• What are the trade-offs?
• Is one preferred over the other?
• What are your thoughts about the first 3 standards?

Answer 1

You want to use the SQL Server driver. I understand what you are trying to do but the way you would accomplish supporting multiple databases is by inserting another layer of abstraction. You can do this many ways. But you put the database specific code at the edge of your class hierarchy. Therefore, each class can get the benefits of database specific functionality but the higher level callers don't know or care what database is being used underneath. As far as ORMs, I prefer LLBLGen, but this is just my preference.

Also, just to clarify, LINQ is not specific to SQL Server. That is LINQ-to-SQL. LINQ is a querying technology that you can use in LINQ-to-SQL, LINQ-to-Entities, LINQ-to-objects, and even LLBLGen supports LINQ.