c# - The type or namespace name 'ClaimsIdentity' could not be found -

i've added these usings , have nuget packages installed. why can not use claim? visual studio says claimsidentity, claim , claimtypes not found.

~/controllers/acccontroller.cs

using microsoft.aspnet.identity; using microsoft.owin.security; using system.threading.tasks; using system.web; using system.web.mvc;  namespace myproject.controllers {     public class acccontroller : controller     {         [allowanonymous]         [httppost]         public actionresult login(loginmodel model)         {             if (!modelstate.isvalid)             {                 return view();             }              // don't in production!             if (model.email == "admin@admin.com" && model.password == "password")             {                 var identity = new claimsidentity(new[] {                 new claim(claimtypes.name, "ben"),                 new claim(claimtypes.email, "a@b.com"),                 new claim(claimtypes.country, "england")             },                     "applicationcookie");                  var ctx = request.getowincontext();                 var authmanager = ctx.authentication;                  authmanager.signin(identity);                  return redirect(getredirecturl(model.returnurl));             }              // user authn failed             modelstate.addmodelerror("", "invalid email or password");             return view();         }     } } 

try add in code:

using system.security.claims;