.net主站和二级域名下实现session共享

    public class CrossDomainCookie : IHttpModule
    {
        private string m_RootDomain = string.Empty;

        #region IHttpModule Members

        public void Dispose()
        {
            
        }

        public void Init(HttpApplication context)
        {
            m_RootDomain = ConfigurationManager.AppSettings["RootDomain"];

            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, m_RootDomain);
            
            context.EndRequest += new System.EventHandler(context_EndRequest);
        }

        void context_EndRequest(object sender, System.EventArgs e)
        {
            HttpApplication app = sender as HttpApplication;

            for (int i = 0; i < app.Context.Response.Cookies.Count; i++)
            {
                app.Context.Response.Cookies[i].Domain = m_RootDomain;
            }
        }

        #endregion
    }

config里面配置：（注意两个站点都要配置）

<configuration>
  <appSettings>
    <add key="RootDomain" value=".session.com"/>
  </appSettings>
  <connectionStrings/>
  <system.web> 
    <machineKey decryptionKey="FD69B2EB9A11E3063518F1932E314E4AA1577BF0B824F369" validationKey="5F32295C31223A362286DD5777916FCD0FD2A8EF882783FD3E29AB1FCDFE931F8FA45A8E468B7A40269E50A748778CBB8DB2262D44A86BBCEA96DCA46CBC05C3" validation="SHA1" decryption="Auto"/>
    <sessionState cookieless="false" timeout="50" mode="StateServer" stateConnectionString="tcpip=127.0.0.1:42424"/>
    <httpModules>
      <add name="CrossDomainCookieModule" type="WebLibrary.CrossDomainCookie, WebLibrary"/>
    </httpModules>
    <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID"/>
  </system.web>
  <!-- 
        The system.webServer section is required for running ASP.NET AJAX under Internet
        Information Services 7.0.  It is not necessary for previous version of IIS.
    -->
  <system.webServer>
    <modules>
      <add name="CrossDomainCookieModule" preCondition="managedHandler" type="WebLibrary.CrossDomainCookie, WebLibrary"/>
    </modules>
  </system.webServer>
</configuration>