困惑不解，请求解决，附上代码

下面是在系统出错时通过log4net写日志的类，但在写WriteEventLog（）写日志的方法中，CurrentSessionInfo的内容永远是
“Anonymous User And System Session is Null”，请问为什么会这样呢？

public class EventLog
{
 #region 私有构造函数，单件模式，防止被实例化
 /// <summary>
 /// 私有构造函数，单件模式，防止被实例化
 /// </summary>
 private EventLog()
 {
 }
 #endregion

 #region 是否启用日志事件跟踪
 /// <summary>
 /// 是否启用日志事件跟踪
 /// </summary>
 protected static bool EnableEvent
 {
 get
 {
 return ConfigInfo.WEB_SYSTEM_ENABLEEVENTLOG;
 }
 }
 #endregion

 #region 事件信息体结构
 /// <summary>
 /// 事件信息体结构
 /// </summary>
 private struct EventBody
 {

 #region 当前会话信息属性
 /// <summary>
 /// 当前会话信息属性
 /// </summary>
 public string CurrentSessionInfo
 {
 get
 {
 StringBuilder SessionInfo = new StringBuilder();

 if (HttpContext.Current != null && HttpContext.Current.Session != null)
 {
 for (int i = 0; i < HttpContext.Current.Session.Count; i++)
 {
 SessionInfo.Append("\r\n\tSession[").Append(HttpContext.Current.Session.Keys[i])
 .Append("] = ").Append(TypeParseHelper.StringParse(NetHelper.CurrentContext.Session[i]));
 }
 }

 if (SessionInfo.Length == 0)
 {
 return "Anonymous User And System Session is Null!";
 }
 else
 {
 return SessionInfo.ToString();
 }
 }
 }
 #endregion

 #region 远程主机IP地址
 /// <summary>
 /// 远程主机IP地址
 /// </summary>
 public string UserHostAddress
 {
 get
 {
 return NetHelper.GetIP();
 }
 }
 #endregion

 #region 出错页面地址
 /// <summary>
 /// 出错页面地址
 /// </summary>
 public string ErrorPage
 {
 get
 {
 return RequestHelper.GetUrl();
 }
 }
 #endregion

 #region 页面来源地址
 /// <summary>
 /// 页面来源地址
 /// </summary>
 public string ReferrerPage
 {
 get
 {
 return RequestHelper.GetUrlReferrer();
 }
 }
 #endregion

 #region 相关变量

 /// <summary>
 /// 事件等级变量
 /// </summary>
 public EventLevelEnum EventLevel;

 /// <summary>
 /// 事件源变量
 /// </summary>
 public EventSourceEnum EventSource;

 /// <summary>
 /// 事件标题变量
 /// </summary>
 public string EventTitle;

 #endregion
 }
 #endregion

 #region 初始化log4net
 /// <summary>
 /// 初始化log4net
 /// </summary>
 public static void Initializelog4net()
 {
 //log4net.Config.DOMConfigurator.Configure();
 log4net.Config.XmlConfigurator.Configure();
 }
 #endregion

 #region 写事件方法
 /// <summary>
 /// 写事件方法
 /// </summary>
 /// <param name="objEventBody">事件信息体</param>
 /// <param name="oExp">事件</param>
 public static void WriteEventLog(EventBody objEventBody, Exception oExp)
 {
 if (!EnableEvent)
 return;

 //事件信息初始化
 StringBuilder strEventMessage = new StringBuilder();
 strEventMessage.Append("内容标题：").Append(objEventBody.EventTitle).Append("\r\n ");
 strEventMessage.Append("远程主机：").Append(objEventBody.UserHostAddress).Append("\r\n ");
 strEventMessage.Append("会话信息：").Append(objEventBody.CurrentSessionInfo).Append("\r\n ");

 log4net.ILog log = log4net.LogManager.GetLogger("Kinyu");

 switch ((EventLogEntryType)objEventBody.EventLevel)
 {
 case EventLogEntryType.Error:
 log.Error(strEventMessage, oExp);
 break;
 case EventLogEntryType.FailureAudit:
 log.Error(strEventMessage, oExp);
 break;
 case EventLogEntryType.Information:
 log.Info(strEventMessage, oExp);
 break;
 case EventLogEntryType.SuccessAudit:
 log.Info(strEventMessage, oExp);
 break;
 default:
 log.Warn(strEventMessage, oExp);
 break;
 }
 }
 #endregion
} --------------------编程问答-------------------- mark！

补充：.NET技术 ,  C#