Why SQL 2008 Express requires .NET Framework 3.5?
Posted: Wed Apr 08, 2009 7:18 am
just like in subject 
Bar_BQ,
3.5 made its first public appearance in VS.Net 2008. If SQL Server 2008 was built using VS.Net 2008 then it's possible they have built it using the 3.5 framework in much the same way SQL Server 2005 would have been built using framework 2.0. Then again MS could have built SQL 2008 using version 2.0 but I suspect they would have opted for 3.5 to leverage the new features in the framework.
I'm not certain what they would use but if you research MS' website they may list specifically what framework they require. When I write applications in VS.Net 2008 I tend to force the 3.5 framework rather than 'back date' the project to version 2.0.
From where I sit: if it's 2008 assume 3.5, otherwise 2.0.
VS.Net 2008 projects can use any framework but I guess the smart money will always bet on 3.5 as the preferred choice.