Prevent to Access Adminpage

Amin Bhr

Hi All
im trying to use Sessions to Authentication of the Admins and Users
but it isnt work
here is my code
i have a database with memberid membername & memberpass & membertype
and i say if membertype=admin then redirect to adminpanel.aspx if membertype=user
then redirect to userpanel.aspx else go to 404.aspx
and i use dbml model datalinksql

protected void ButtonLogin_Click(object sender, EventArgs e)
    {
        EshopDataClassesDataContext db = new EshopDataClassesDataContext();
        Member UserOne = db.Members.Where(t => t.MemberUser == txtUser0.Text && t.MemberPass == txtPass0.Text).FirstOrDefault();
        if (UserOne != null)
        {
            Session["MemberId"] = UserOne.MemberId.ToString();
            Session["MemberType"] = UserOne.MemberType;
            Session["MemberUser"] = UserOne.MemberUser;
            if (UserOne.MemberType == "Admin")
            {
                Response.Redirect("~/Admin/AdminPanel.aspx");
            }
            else if (UserOne.MemberType == "User") { Response.Redirect("~/User/UserPanel.aspx"); }
            else
            {
                Label1.Visible = true;
            }
        }
    }

and in my adminpanel page i trying to use this

if (Session["MemberType"] != null && Session["MemberType"].ToString() == "Admin")
        {
            Response.Redirect("~/Admin/AdminPanel.aspx");
        }
        else if (Session["MemberType"] != null && Session["MemberType"].ToString() == "User")
        {
            Response.Redirect("~/User/UserPanel.aspx");
        }
        else
        {
            Response.Redirect("~/404.aspx");
        }

it will redirect me to adminpage when i logged in but show erorr : this page is not working
but without these codes everything is ok ! why? what can i do?