对于具有Asp.NET Identity 2.0的MVC 5,您需要执行两个步骤：

>定义自定义OnValidateIdentity,提取cookie信息,并将其保留为声明.

public class Startup
{
  public void Configuration(IAppBuilder app)
  {
    app.UseCookieAuthentication(new CookieAuthenticationOptions
    {
      AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,Provider = new CookieAuthenticationProvider
      {
        OnValidateIdentity = MyCustomValidateIdentity //refer to the implementation below
      }
    }
  }


  // this method will be called on every request
  // it is also one of the few places where you can access unencrypted cookie content as CookieValidateIdentityContext
  // once you get cookie information you need,keep it as one of the Claims
  // please ignore the MyUserManager and MyUser classes,they are only for sample,you should have yours
  private static Task MyCustomValidateIdentity(CookieValidateIdentityContext context)
  {
    // validate security stamp for 'sign out everywhere'
    // here I want to verify the security stamp in every 100 seconds.
    // but I choose not to regenerate the identity cookie,so I passed in NULL 
    var stampValidator = SecurityStampValidator.OnValidateIdentity<MyUserManager<Myuser>. MyUser>(TimeSpan.FromSeconds(100),null); 
    stampValidator.Invoke(context);

    // here we get the cookie expiry time
    var expireUtc = context.Properties.ExpiresUtc;

    // add the expiry time back to cookie as one of the claims,called 'myExpireUtc'
    // to ensure that the claim has latest value,we must keep only one claim
    // otherwise we will be having multiple claims with same type but different values
    var claimType = "myExpireUtc";
    var identity = context.Identity;
    if(identity.HasClaim(c=> c.Type == claimType))
    {
      var existingClaim = identity.FindFirst(claimType);
      identity.RemoveClaim(existingClaim); 
    }
    var newClaim = new Claim(claimType,expireUtc.Value.UtcTicks.ToString());
    context.Identity.AddClaim(newClaim);

    return Task.FromResult(0);
  }
}

>在控制器方法中访问您的声明

// since expiry time has now become part of your claims,you now can get it back easily
// this example just returns the remaining time in total seconds,as a string value
// assuming this method is part of your controller methods

public string RemainingTime()
{
  var identity = User.Identity as ClaimsIdentity;
  var claimType = "myExpireUtc";  //NOTE: must be the same key value "myExpireUtc" defined in code shown above

  if(identity != null && identity.HasClaim(c=> c.Type == claimType))
  { 
    var expireOn = identity.FindFirstValue(claimType); 

    DateTimeOffset currentUtc = DateTimeOffset.UtcNow;
    DateTimeOffset? expireUtc = new DateTimeOffset(long.Parse(expireOn),TimeSpan.Zero);

    var remaining = (expireUtc.Value - currentUtc).TotalSeconds;

    return remaining.ToString();
  }
  return string.Empty;
}

我使用这种方法提醒我的应用程序用户在会话超时之前扩展会话.

感谢这篇文章How do I access Microsoft.Owin.Security.xyz OnAuthenticated context AddClaims values?