private void btn_Add_ItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e)
        {
            frm_RegisterUser f = new frm_RegisterUser();

            f.FormClosed += new FormClosedEventHandler(dongformEmployee);

            f.ShowDialog();
        }
        private void btnRegistered_ItemClick(object sender, ItemClickEventArgs e)
        {
            Form frm = kiemtraform(typeof(frm_RegisterUser));

            if (frm == null)
            {
                frm_RegisterUser forms = new frm_RegisterUser( );
                forms.MdiParent = this;
                forms.Show( );
            }
            else
            {
                frm.Activate( );
            }
        }