ERROR:1.引发类型为“System.Web.HttpUnhandledException”的异常。 
2.An error occurred accessing the database. This usually means that the connection to the database failed. Check that the connection string is correct and that the appropriate DbContext constructor is being used to specify it or find it in the application's config file. See http://go.microsoft.com/fwlink/?LinkId=386386 for information on DbContext and connections. See the inner exception for details of the failure. 
3.The provider did not return a ProviderManifestToken string. 
4.Unable to connect to any of the specified MySQL hosts.