protected void Page_Load(object sender, EventArgs e)
        {
private string ids = "";
ids = Session["username"].ToString();  //报错的地方
}protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
        {
            if (e.CommandName == "upds")
            {
                string idss = "";
                string ids = e.CommandArgument.ToString();
                Response.Redirect("OAjobplansystem.aspx?Id=" + ids);
                idss = Request.QueryString["ids"];
                Session["username"] = idss;
            }
        }