private static Task<bool> VerifyClientIdAsync(ApplicationUserManager manager, ApplicationUser user, CookieValidateIdentityContext context)
        {
            string clientId = context.Identity.FindFirstValue("AspNet.Identity.ClientId");
            if (!string.IsNullOrEmpty(clientId) && user.Clients.Any(c => c.Id.ToString() == clientId))
            {
                user.CurrentClientId = clientId;
                return Task.FromResult(true);
            }

            return Task.FromResult(false);
        }
 private static async Task<bool> VerifySecurityStampAsync(ApplicationUserManager manager, ApplicationUser user, CookieValidateIdentityContext context)
 {
     string stamp = context.Identity.FindFirstValue("AspNet.Identity.SecurityStamp");
     return (stamp == await manager.GetSecurityStampAsync(context.Identity.GetUserId()));
 }