Page_PreRender

protected void Page_PreRender(object sender, EventArgs e)
{
    HFKC.PublicClass.Message.MessageBox(pdlProjList.SelectValue, this);
}

 protected void Page_Load(object sender, EventArgs e)
 {
      if (!IsPostBack)
       {
            SetBehindMsg();
            SetPageInitControl();
            BindpdlProjList();
       }   
}

First Page_Load then PreRender