未设置为对象实例的对象引用.在step

我想把用户的IP和活动保存在一个名为logPublic的表中，我想当一个未经认证的用户试图访问一个特殊的文件夹，例如Admin文件夹，我可以在logPublic表中添加一个记录，它有一些字段为e,g: ID,IP，活动，日期时间。之后，未经认证的用户将被自动锁定

我使用下面的代码在Load_Page事件的主页在管理文件夹:

$public partial class Admin : System.Web.UI.MasterPage 
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        if (!HttpContext.Current.User.Identity.IsAuthenticated)
        {
            Session["IsBlocked"] = true;
            string ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            HttpContext.Current.Session["UserIP"] = ip;
            HttpContext.Current.Session["Activity"] = HttpContext.Current.Request.Url;
            HttpContext.Current.Session["DateTime"] = System.DateTime.Now;
        }
        else
        {
            if(! HttpContext.Current.User.IsInRole("Admin"))
            {
            Session["BlockUser"] = true;
            string ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            HttpContext.Current.Session["UserIP"] = ip;
          }
        }

    }
}

$namespace StoreProject.Data
{
    public class CustomSecurityModule :IHttpModule
    {
     storedbEntities StoreEnt = new storedbEntities();
    public void Dispose()
    {
        throw new NotImplementedException();
    }
    public void Init(HttpApplication context)
    {
        //throw new NotImplementedException();
        context.BeginRequest += new EventHandler(this.app_DoSecuriy);
    }
    private void app_DoSecuriy(object sender, EventArgs e)
    {
        // Create HttpApplication and HttpContext objects to access
        // request and response properties.
        HttpApplication application = (HttpApplication)sender;
        HttpContext context = application.Context;
       storedbEntities StoreEnt = new storedbEntities();
        if (context.Session["BlockUser"]!= null &&  Convert.ToBoolean(context.Session["BlockUser"])== true)
        {
                logPrivate Log = new logPrivate()
                 {
                     Username = context.User.Identity.Name,
                     IP = context.Session["UserIP"].ToString(),
                     Enter = System.DateTime.Now,
                 };
                StoreEnt.logPrivates.AddObject(Log);
                StoreEnt.SaveChanges();
                context.Response.Redirect("~/UnAuthorizedAccess.aspx");

        }
        //ublock != null && bool.TryParse(ublock.ToString(),out isblocked) && isblocked
        else if ( context.Session["BlockPublick"] != null 
                 && System.Convert.ToBoolean(context.Session["BlockPublick"]) == true)
        {
            LogPublic newLog = new LogPublic()
            {
                IP = context.Session["UserIP"].ToString(),
                Activity = context.Session["Activity"].ToString(),
                Enter = Convert.ToDateTime(context.Session["DateTime"])
            };
            StoreEnt.LogPublics.AddObject(newLog);
            StoreEnt.SaveChanges();
            context.Response.Redirect("~/UnAuthorizedAccess.aspx");
        }

        }
    }
}

但是当我运行我的应用程序网站时，我从httpmodule得到一个错误:对象引用未设置为对象的实例。

if (context.Session["BlockUser"]!= null 
  &&  Convert.ToBoolean(
        context.Session["BlockUser"])== true)

我没有任何记录在LogPublic表或logPrivate表，当我想要访问一个页面在管理文件夹请指引我

谢谢