WIF on Windows XP and Cassini

WIF isn’t officially supported on XP (and it won’t even install), but you can ~/bin deploy it (you need to for Azure deployment). So this means you can basically develop with WIF on XP, but if you’re using Cassini as your web server then you’ll run into this bizarre exception (with a lousy stack trace too):

“Type is not resolved for member Microsoft.IdentityModel.Claims.ClaimsPrincipal”

Turns out that it’s an issue with Cassini and custom IIdentity implementations. One workaround is to copy Microsoft.IdentityModel.dll to “C:\Program Files\Common Files\Microsoft Shared\DevServer\10.0″. The other workaround is to GAC install Microsoft.IdentityModel.dll.