Just do Copy Local = true in the properties for the assembly(System.Web.Http.WebHost) and then do a redeploy, it should work fine.
http://stackoverflow.com/questions/20323107/could-not-load-file-or-assembly-system-web-http-webhost-after-published-to-azure
原文：http://www.cnblogs.com/maizhongfei/p/5467299.html