不同二级域名下多站点会话（Session）共享

web.config配置如下：

IIS6：

  <system.web>

    <sessionState mode="StateServer" stateConnectionString="tcpip=192.168.1.60:42424" timeout="30" />

    <httpModules>
      <add name="SessionSharedHttpModule" type="Myun.Web.SessionSharedHttpModule, Myun.Web" />
    </httpModules>

  </system.web>

IIS7：托管管道模式为 集成管道模式，否则与IIS6相同

  <system.web>

    <sessionState mode="StateServer" stateConnectionString="tcpip=192.168.1.60:42424" timeout="30" />

  </system.web>

 <system.webServer>

    <modules>
      <add name="SessionSharedHttpModule" type="Myun.Web.SessionSharedHttpModule, Myun.Web" />
    </modules>

 </system.webServer>

代码如下：SessionSharedHttpModule.cs

//****************************//

//create date：2011-05-14

//****************************//

namespace Myun.Web
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Web.SessionState;
    using System.Reflection;
    /// <summary>
    /// 二级域名会话共享
    /// </summary>
    public class SessionSharedHttpModule : IHttpModule
    {
        string _rootDomain = null; //一级域名


        public void Dispose()
        {
            //throw new NotImplementedException();
        }

        public void Init(HttpApplication context)
        {
            _rootDomain = "dhlx.cn"; //一级域名赋值

            //去除一级域名以外信息（将www.dhlx.cn改为dhlx.cn，如果一级域名不是常量赋值的话）
            //_rootDomain = _rootDomain.Substring(_rootDomain.LastIndexOf('.', _rootDomain.LastIndexOf('.') - 1) + 1);
            
            //要实现会话共享还得修改OutOfProcSessionStateStore类下的一个私有的静态字段s_uribase
            //OutOfProcSessionStateStore的声明为：
            //internal sealed class OutOfProcSessionStateStore : SessionStateStoreProviderBase
            //s_uribase的声明为：
            //static string       s_uribase;
            //关于OutOfProcSessionStateStore类以及s_uribase字段的内容请查阅OutOfProcStateClientManager.cs文件
            //文件路径：Framework源代码\V2.0.5727\dd\ndp\fx\src\xsp\System\Web\State\OutOfProcStateClientManager.cs
            Type stateServerSessionProvider = typeof(HttpSessionState).Assembly.GetType("System.Web.SessionState.OutOfProcSessionStateStore");
            FieldInfo uriField = stateServerSessionProvider.GetField("s_uribase", BindingFlags.Static | BindingFlags.NonPublic);
            if (uriField == null)
                throw new ArgumentException("UriField was not found");

            uriField.SetValue(null, _rootDomain);
            context.EndRequest += new EventHandler(context_EndRequest);   

        }

        /// <summary>
        /// 从发送给客户端的Cookie集合中找出记录会话ID的Cookie
        /// 并修改它的Domain属性值为要共享的一级域名
        /// </summary>

        void context_EndRequest(object sender, System.EventArgs e)
        {
            HttpApplication app = sender as HttpApplication;
            for (int i = app.Context.Response.Cookies.Count - 1; i >= 0; i--)
            {

                //ASP.NET_SessionId是默认的存储会话ID的key，如果修改了默认值这里要修改成一致的
                if (app.Context.Response.Cookies[i].Name.Equals("ASP.NET_SessionId"))
                {
                    app.Context.Response.Cookies[i].Domain = _rootDomain;
                    return;
                }
            }
        }
    }
}

//http://hi.baidu.com/qinmingyun/blog/item/93eafbcadb2fd61893457e63.html