Applicationsigninmanager could not be found?

<pre>using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.Owin;
using Microsoft.Owin.Security.Cookies;
using Owin;
using eNtsaTrainingRegistration.Models;

namespace eNtsaTrainingRegistration
{
    public partial class Startup
    {
        public void ConfigureAuth(IAppBuilder app)
        {
            app.CreatePerOwinContext(ApplicationDbContext.Create);
            app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);
        }
    }
}

public class ApplicationSignInManager:SignInManager<ApplicationUser, string>
     {
         public ApplicationSignInManager(ApplicationUserManager userManager, IAuthenticationManager authenticationManager)
         : base(userManager, authenticationManager)
         {
         }

         public override Task<ClaimsIdentity> CreateUserIdentityAsync(ApplicationUser user)
         {
             return user.GenerateUserIdentityAsync((ApplicationUserManager)UserManager);
         }

         public static ApplicationSignInManager Create(IdentityFactoryOptions<ApplicationSignInManager> options, IOwinContext context)
         {
             return new ApplicationSignInManager(context.GetUserManager<ApplicationUserManager>(), context.Authentication);
         }
     }