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ASP.NET MVC“甜甜圈缓存”和tempdata

asp.net-mvc asp.net

eu-ge-ne · 技术社区 · 15 年前

在httpResponseBase.WriteSubstitution()方法中是否有访问tempData属性的解决方案?

这不起作用:

<%= Response.WriteSubstitution(x => Html.Encode(TempData["message"].ToString())) %>

但这是可行的:

<%= Response.WriteSubstitution(x => DateTime.Now.ToString()) %>

对于一次缓存的页面,请求处理中存在问题。根据 http://msdn.microsoft.com/en-us/library/system.web.httpresponse.writesubstitution.aspx :

在对页面的第一个请求上,writesubstitution调用httpResponseSubstitutionCallback委托以生成输出。然后,它在响应中添加了一个替换缓冲区,该缓冲区保留委托以调用未来的请求。最后,它降低了客户端从公共缓存到服务器的可缓存性,确保将来对页面的请求通过不在客户端上缓存来重新调用委托。

换句话说,委托无权访问会话属性(sessionstatetempdataprovider在会话中存储tempdata),因为没有“正常”的请求生命周期。据我所知,它是在httpapplication.resolverequestcache/httpapplication.postpresolverequestcache事件中处理的,但当前状态是在httpapplication.acquireRequestState事件中获取的。( http://msdn.microsoft.com/en-us/library/ms178473.aspx )

也许我需要某种“高级定制tempdataprovider”:)有什么想法吗?

1 回复 | 直到 15 年前

Jeff Atwood 15 年前

我找到了解决方案:

主要的想法是将tempdata的副本保存在缓存中,并在每次请求时检索它。解决方案是自定义tempdataprovider和简单HTTP模块的组合。另外还有几个助手和静态类。

代码如下:

自定义临时数据提供程序:

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Caching;
using System.Web.Mvc;

public class CustomTempDataProvider : SessionStateTempDataProvider, IHttpModule
{
    public void Init(HttpApplication application)
    {
        application.BeginRequest += new EventHandler(application_BeginRequest);
    }

    void application_BeginRequest(object sender, EventArgs e)
    {
        var httpContext = HttpContext.Current;
        var tempData = httpContext.Cache[TempDataKey] ?? new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
        httpContext.Items.Add("TempData", tempData);
        httpContext.Cache.Remove(TempDataKey);
    }

    public override void SaveTempData(ControllerContext controllerContext,
        IDictionary<string, object> values)
    {
        HttpContext.Current.Cache.Insert(TempDataKey, values, null, DateTime.Now.AddMinutes(5), Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, null);
        base.SaveTempData(controllerContext, values);
    }

    public static string TempDataKey
    {
        get
        {
            string sessionID = "0";
            var httpContext = HttpContext.Current;
            if(httpContext.Session != null)
            {
                sessionID = httpContext.Session.SessionID;
            }
            else if (httpContext.Request.Cookies["ASP.NET_SessionId"] != null)
            {
                sessionID = httpContext.Request.Cookies["ASP.NET_SessionId"].Value;
            }
            return "TempData-For-Session-" + sessionID;
        }
    }

    public void Dispose()
    {
    }
}

在web.config中注册:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.web>
        <httpModules>
            <add name="CustomTempDataProvider" type="CustomTempDataProvider" />
        </httpModules>
    </system.web>
    <system.webServer>
        <modules>
            <remove name="CustomTempDataProvider" />
            <add name="CustomTempDataProvider" type="CustomTempDataProvider" />
        </modules>
    </system.webServer>
</configuration>

自定义控制器工厂:

using System.Web.Routing;
using System.Web.Mvc;

public class CustomControllerFactory : DefaultControllerFactory
{
    public override IController CreateController(
        RequestContext requestContext, string controllerName)
    {
        var controller = (Controller)base.CreateController(requestContext, controllerName);
        controller.TempDataProvider = new CustomTempDataProvider();
        return controller;
    }
}

在global.asax中注册:

protected void Application_Start()
{
    RegisterRoutes(RouteTable.Routes);

    ControllerBuilder.Current.SetControllerFactory(typeof(CustomControllerFactory));
}

用于访问tempdata的静态类:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

public static class CustomTempData
{
    public static object Get(string key)
    {
        var tempData = HttpContext.Current.Items["TempData"] as IDictionary<string, object>;
        var item = tempData.FirstOrDefault(x => x.Key == key).Value ?? String.Empty;
        return item;
    }
}

后缓存替换帮助程序:

using System;
using System.Web;
using System.Web.Mvc;

public static class Html
{
    public delegate object MvcResponseSubstitutionCallback(HttpContextBase context);

    public static object MvcResponseSubstitute(this HtmlHelper html, MvcResponseSubstitutionCallback callback)
    {
        html.ViewContext.HttpContext.Response.WriteSubstitution(
            context =>
                HttpUtility.HtmlEncode(
                    (callback(new HttpContextWrapper(context)) ?? String.Empty).ToString()
                )
            );

        return null;
    }
}

现在这项工作成功:

<h3><%= Html.MvcResponseSubstitute(context => CustomTempData.Get("message")) %></h3>

如果你懂俄语,请阅读 this

希望这有帮助