c# - Error CS0122 'AuthenticationOptions' is inaccessible due to its protection level -

i following guide write own katana authentication middleware.

now encountered problem when i'm writing authenticationoptions. "inaccessible due protection level" when inherent microsoft.owin.security.authenticationoptions. thing class protected, should not inaccessible? have tried clean , rebuild, still same error. must missing something?

my class:

using microsoft.owin; using microsoft.owin.security; using system; using system.collections.generic; using system.linq; using system.text; using system.threading.tasks;  namespace dummy {     public class dummyauthenticationoptions : authenticationoptions     {         public dummyauthenticationoptions(string username, string userid)             : base(constants.defaultauthenticationtype)         {             description.caption = constants.defaultauthenticationtype;             callbackpath = new pathstring("/signin-dummy");             authenticationmode = authenticationmode.passive;             username = username;             userid = userid;         }          public pathstring callbackpath { get; set; }          public string username { get; set; }          public string userid { get; set; }          public string signinasauthenticationtype { get; set; }          public isecuredataformat<authenticationproperties> statedataformat { get; set; }     } } 

microsoft.owin.security.authenticationoptions:

namespace microsoft.owin.security {     internal abstract class authenticationoptions     {         protected authenticationoptions(string authenticationtype);          public authenticationmode authenticationmode { get; set; }         public string authenticationtype { get; set; }         public authenticationdescription description { get; set; }     } } 

the problem authenticationoptions class set internal. downgraded microsft.owin.security package 3.0.1 2.0.1. here class marked public able compile without problems.

thanks dmitry rotay