No, it should still build and run OK in VC# 2008 Express or VS 2008.
Although the .NET Framework has moved on from version 2.0 to 3.5 and C# itself from version 2.0 to 3.0, they are backwards compatible with the 2005 versions.
In fact VS 2008 can target versions 2.0, 3.0 or 3.5 of the .NET Framework, if needed.