You may be in for a surprise when you try to rebuild your strongly named assemblies written in C# under Whidbey for the first time. If you're using the AssemblyKeyFile attribute, you'll get a warning similar to this:
Warning CS1699 directs you to use the C# compiler's /keyfile option to sign your assemblies, rather than using the AssemblyKeyFile attribute. Although AssemblyKeyFileAttribute will still work on Whidbey, it's recommended you move to /keyfile for several reasons.
Fixing this for Whidbey will be relatively painless, just remove the attributes and set the compile flag in your build system. If you're using Visual Studio to build, from the project properties you can go to the new signing tab, and select the key you want to use. This page will also let you generate and password protect a new key. In addition to key files, the signing property page has options to delay sign or use a key container.
As a last resort, if these warnings are blocking you from getting builds out, you can temporarily disable them using code like the following:
This change also affects key containers as well; you'll get the warning 1699 unless you switch to using the /keycontainer command line switch.