一段时间后会话变量变为空

Question

我已经开发了一个 web 应用程序，它将执行一些图像的幻灯片放映。我有这个应用程序的 jquery ajax web 方法调用

图像滚动完美......但一段时间后它停止了......我从日志中发现我的会话变量（这里是 Session[“Username”]）正在变为 null。我的代码是

   [WebMethod]
    [ScriptMethod]
    public static string GetNextImage()
    {
        try
        {

            if (HttpContext.Current.Session["Username"] != null)
            {
                string username = HttpContext.Current.Session["Username"].ToString();
                RollingScreenBAL bal = new RollingScreenBAL();
                DetailsForSlideShow[] details = bal.GetDetailsForSlideShow(username);
                int count = details.Length;
                int i;

                for (i = 0; i < count; i++)
                {
                    if (HttpContext.Current.Session["Count"] == null)
                    {

                        HttpContext.Current.Session["GraphUrl"] = details[0].GraphUrl;
                        HttpContext.Current.Session["Count"] = i + 1;
                        break;
                    }
                    else
                    {
                        if (Convert.ToInt32(HttpContext.Current.Session["Count"]) == i)
                        {
                            HttpContext.Current.Session["GraphUrl"] = details[i].GraphUrl;
                            if (i == (count - 1))
                            {
                                HttpContext.Current.Session["Count"] = null;
                            }
                            else
                            {
                                HttpContext.Current.Session["Count"] = i + 1;
                            }
                            break;

                        }
                    }


                }

            }
            return HttpContext.Current.Session["GraphUrl"].ToString();



        }
        catch (Exception ex)
        {

            ConfigurationManager configMgr = new ConfigurationManager();
            string traceFilePath = configMgr.GetTraceFilePath();
            StreamWriter traceFile = new StreamWriter(traceFilePath, true);
            traceFile.WriteLine(ex.Message + "\n" + ex.StackTrace + "Current User is  " + **HttpContext.Current.Session["Username"])**;
            traceFile.Close();
            return ex.Message;
        }
    } 

HttpContext.Current.Session["Username"]) 会话值变为空..谁能帮我为什么它会变为空？提前谢谢...

Answer 1

当会话超时（并且未重新建立/重新初始化）时，或者当您将会话字典中的特定项目显式设置为 null 时，您的会话变量变为 null。