The order of C# switch case statements in your code has no effect on performance.
Microsoft has released Service Pack 1 for Visual Studio 2008 and .NET 3.5. This update patches numerous bugs, improves performance, and even adds a few new features.
As a .NET commercial software developer, I am most excited that SP1 provides a .NET Framework installation optimized for client applications. The optimized download is less than 28 MB, compared to the original 200 MB download that all but ensured consumers would not download .NET 3.5 and hence forced us to remain on .NET 2.0 (see FAT .NET).