protected void Page_Load(object sender, EventArgs e)
        {
            if(Session["User"] != null)
            {
                var user = (User)Session["User"];
                txtbox_username.Enabled = false;
                txtbox_username.Text = user.UserName;
                txtbox_firstname.Text = user.FirstName;
                txtbox_lastname.Text = user.LastName;
                txtbox_email.Text = user.Email;
                txtbox_streetadress.Text = user.StreetAdress;
                txtbox_city.Text = user.City;
                txtbox_zipcode.Text = user.ZipCode.ToString();


            }
            else
            {
                Response.Redirect("Home.aspx");
            }
        }

        protected void btn_savechanges_Click(object sender, EventArgs e)
        {
            var bll = new BLLUser();
            var user = (User)Session["User"];
            user.FirstName = txtbox_firstname.Text;
            user.LastName = txtbox_lastname.Text;
            user.Email = txtbox_email.Text;
            user.StreetAdress = txtbox_streetadress.Text;
            user.City = txtbox_city.Text;
            user.ZipCode = Convert.ToInt32(txtbox_zipcode.Text);
            Session["User"] = user;

            bll.UpdateUser(user);
        }