如何在 ASP.NET MVC 中为错误页面指定 max-age

Question

当我的 ASP.NET MVC 服务器（IIS 上的运行）发生错误时，服务器当前提供静态页面。这是在我的 web.config 中的 httpErrors 元素中配置的，像这样：

<httpErrors errorMode="Custom" existingResponse="Replace">
  <error statusCode="404" path="404.htm" responseMode="File" />
  <error statusCode="500" path="500.htm" responseMode="File" />
</httpErrors>

检查来自服务器的响应时，我看到 cache-control: private 响应 header。这很好，但我想控制此页面的缓存时间。如何将 max-age=x 添加到此 cache-control header？

Answer 1

我尝试了很多方法，但似乎只有当我为 404 错误设置自定义错误页面时它才有效。

<system.webServer>
  <httpProtocol>
        <customHeaders>
            <add name="Cache-Control" value="max-age:12300" />
        </customHeaders>
    </httpProtocol>
</system.webServer>

Answer 2

如果我正确理解你的问题陈述，你的主要目标是控制 max-age，而不是花哨的 <customErrors> 设置。尝试从动作过滤器控制 header 似乎合乎逻辑。

在web.config

我有这个 system.web 设置：

<system.web>
  <compilation debug="true" targetFramework="4.6.1"/> <!-- framework version for reference -->
  <httpRuntime targetFramework="4.6.1"/>
  <customErrors mode="On">
  </customErrors> <!-- I didn't try adding custom pages here, but this blog seem to have a solution: https://benfoster.io/blog/aspnet-mvc-custom-error-pages -->
</system.web>

在MaxAgeFilter.cs

public class MaxAgeFilter : ActionFilterAttribute, IResultFilter, IExceptionFilter
{
    public void OnException(ExceptionContext filterContext)
    {
        if (filterContext.ExceptionHandled || filterContext.HttpContext.IsCustomErrorEnabled)
            return;

        var statusCode = (int)HttpStatusCode.InternalServerError;
        if (filterContext.Exception is HttpException)
        {
            statusCode = (filterContext.Exception as HttpException).GetHttpCode();
        }
        else if (filterContext.Exception is UnauthorizedAccessException)
        {
            statusCode = (int)HttpStatusCode.Forbidden;
        }

        var result = CreateActionResult(filterContext, statusCode);
        filterContext.Result = result;

        // Prepare the response code.
        filterContext.ExceptionHandled = true;
        filterContext.HttpContext.Response.Clear();
        filterContext.HttpContext.Response.StatusCode = statusCode;
        filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;

        var cache = filterContext.HttpContext.Response.Cache;            
        cache.SetMaxAge(TimeSpan.FromSeconds(10)); // this requires a lot of extra plumbing which I suspect is necessary because if you were to rely on default error response - the cache will get overriden, see original SO answer: https://whosebug.com/questions/8144695/asp-net-mvc-custom-handleerror-filter-specify-view-based-on-exception-type
    }

    public override void OnResultExecuted(ResultExecutedContext filterContext)
    {            
        var cache = filterContext.HttpContext.Response.Cache;         
        cache.SetMaxAge(TimeSpan.FromMinutes(10)); // this is easy - you just pass it to the current cache and magic works
        base.OnResultExecuted(filterContext);
    }

    protected virtual ActionResult CreateActionResult(ExceptionContext filterContext, int statusCode)
    {
        var ctx = new ControllerContext(filterContext.RequestContext, filterContext.Controller);
        var statusCodeName = ((HttpStatusCode)statusCode).ToString();

        var viewName = SelectFirstView(ctx,
            "~/Views/Shared/Error.cshtml",
            "~/Views/Shared/Error.cshtml",
            statusCodeName,
            "Error");

        var controllerName = (string)filterContext.RouteData.Values["controller"];
        var actionName = (string)filterContext.RouteData.Values["action"];
        var model = new HandleErrorInfo(filterContext.Exception, controllerName, actionName);
        var result = new ViewResult
        {
            ViewName = viewName,
            ViewData = new ViewDataDictionary<HandleErrorInfo>(model),
        };
        result.ViewBag.StatusCode = statusCode;
        return result;
    }

    protected string SelectFirstView(ControllerContext ctx, params string[] viewNames)
    {
        return viewNames.First(view => ViewExists(ctx, view));
    }

    protected bool ViewExists(ControllerContext ctx, string name)
    {
        var result = ViewEngines.Engines.FindView(ctx, name, null);
        return result.View != null;
    }
}

如您所见，处理异常基本上需要重建整个Response。为此，我几乎从 SO answer here

中获取了代码

最后，您决定是否要在您的控制器、操作或全局设置此属性：

App_Start/FilterConfig.cs

public class FilterConfig
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new MaxAgeFilter());
    }
}

Answer 3

如果您使用的是自定义错误页面，则可以在视图中设置 headers。正如您所说，这样您就可以根据显示的错误页面设置不同的缓存长度。

@{
    TimeSpan duration = new TimeSpan(0, 30, 0);
    Response.Cache.SetMaxAge(duration);
}

如何在 ASP.NET MVC 中为错误页面指定 max-age

How to specify max-age for error pages in ASP.NET MVC

iis

asp.net-mvc

cache-control

iis-10

在web.config

在MaxAgeFilter.cs

App_Start/FilterConfig.cs