如何在ASP.NET MVC中为经过身份验证的用户关闭输出缓存？

Question

我有一个ASP.NET MVC应用程序。 我需要缓存一些页面，但仅限于未经过身份验证的用户。

我尝试使用VaryByCustom="user"和以下GetVaryByCustomString实现：

public override string GetVaryByCustomString(HttpContext context, string custom)
{
  if (custom == "user")
  {
      if (context.User.Identity.IsAuthenticated)
      {
        return context.User.Identity.Name;
      }
      else
      {
        return "";
      }
  }  

  return base.GetVaryByCustomString(context, custom);
}

然而，这并不是我需要的，因为页面仍然被缓存。 唯一的区别是现在分别为每个用户缓存。

一种可能的解决方案是每次用户进行身份验证时返回Guid.NewGuid() ，但这对我来说似乎是一种巨大的资源浪费。

所以你有什么提示吗？

Answer 1

所以这就是我所做的：

public class NonAuthenticatedOnlyCacheAttribute : OutputCacheAttribute
{
    public override void OnResultExecuting(ResultExecutingContext filterContext)
    {
      var httpContext = filterContext.HttpContext;

      if (httpContext.User.Identity.IsAuthenticated)
      {
        // it's crucial not to cache Authenticated content
        Location = OutputCacheLocation.None;
      }

      // this smells a little but it works
      httpContext.Response.Cache.AddValidationCallback(IgnoreAuthenticated, null);

      base.OnResultExecuting(filterContext);
    }

    // This method is called each time when cached page is going to be
    // served and ensures that cache is ignored for authenticated users.
    private void IgnoreAuthenticated(HttpContext context, object data, ref HttpValidationStatus validationStatus)
    {
      if (context.User.Identity.IsAuthenticated)            
        validationStatus = HttpValidationStatus.IgnoreThisRequest;          
      else          
        validationStatus = HttpValidationStatus.Valid;          
    }
}

非常感谢Craig Stuntz向我指出了正确的方向，我的答案在不知不觉中被低估了。

Answer 2

通常会对属性进行缓存，然后您需要存储原始位置。 如果您访问Logged页面，它将Location设置为None，然后当您以匿名方式访问时，它仍然是None。

public class AuthenticatedOnServerCacheAttribute : OutputCacheAttribute
{
    private OutputCacheLocation? originalLocation;

    public override void OnResultExecuting(ResultExecutingContext filterContext)
    {
        var httpContext = filterContext.HttpContext;

        if (httpContext.User.Identity.IsAuthenticated)
        {
            originalLocation = originalLocation ?? Location;
            Location = OutputCacheLocation.None;
        }
        else
        {
            Location = originalLocation ?? Location;
        }

        base.OnResultExecuting(filterContext);
    }
}

Answer 3

接受的答案是正确的，但它不适用于以这种方式缓存部分视图。 我结合了两种变体： GetVaryByCustomString并将Duration设置为最小 - 对于页面的部分视图和AddValidationCallback方法。 实际上可以只使用第一种方法，但第二种方法看起来不那么昂贵 - 它不会每次调用OnResultExecuting而只调用注册处理程序。

所以自定义缓存属性类

public class CacheAttribute : OutputCacheAttribute
{   

    public CacheAttribute()
    {
      Duration = 300;  /*default cache time*/
    }

    private bool _partialView;

    /// <summary>
    /// Set true if Partial view is cached
    /// </summary>
    public bool PartialView
    {
      get { return _partialView; }
      set
      {
        _partialView = value;
        if ( _partialView ) {
          VaryByCustom = "Auth";
        }
      }
    }

    public override void OnResultExecuting(ResultExecutingContext filterContext)
    {
        if ( PartialView ) OnCachePartialEnabled( filterContext );
        else OnCacheEnabled(filterContext);

        base.OnResultExecuting( filterContext );     
    }

    private OutputCacheLocation? originalLocation;
    private int? _prevDuration;
    protected void OnCachePartialEnabled(ResultExecutingContext filterContext)
    {
      var httpContext = filterContext.HttpContext;

      if ( !_prevDuration.HasValue) _prevDuration = Duration;
      Duration = httpContext.User.Identity.IsAuthenticated ? 1 : _prevDuration.Value;
    }

    protected void OnCacheEnabled(ResultExecutingContext filterContext)
    {
      var httpContext = filterContext.HttpContext;

      if ( httpContext.User.Identity.IsAuthenticated ) {
        // it's crucial not to cache Authenticated content
        originalLocation = originalLocation ?? Location;
        Location = OutputCacheLocation.None;
      }
      else {
      Location = originalLocation ?? Location;
    }

      // this smells a little but it works
      httpContext.Response.Cache.AddValidationCallback( IgnoreAuthenticated, null );      
    }

    // This method is called each time when cached page is going to be
    // served and ensures that cache is ignored for authenticated users.
    private void IgnoreAuthenticated(HttpContext context, object data, ref HttpValidationStatus validationStatus)
    {
      validationStatus = context.User.Identity.IsAuthenticated 
        ? HttpValidationStatus.IgnoreThisRequest 
        : HttpValidationStatus.Valid;
    }
}

覆盖Global.asax.cs中的GetVaryByCustomString方法

public override string GetVaryByCustomString(HttpContext context, string custom)
{ 
    if ( custom == "Auth" ) {
      //do not cache when user is authenticated
      if ( context.User.Identity.IsAuthenticated ) {
        return base.GetVaryByCustomString( context, custom );
      }
      return "NotAuth";
    }     
    return base.GetVaryByCustomString( context, custom );
}

像这样使用它：

[Cache]
public virtual ActionResult Index()
{
    return PartialView();
}

[ChildActionOnly, Cache(PartialView=true)]
public virtual ActionResult IndexPartial()
{
    return PartialView();
}

更新：我还在这里添加了Fujiy的修复程序