public void ThemMavach() { DataTable _dt = new DataTable(); Dto_user = new DTO_User(); Dto_user.User = txtU.Text.Trim(); Dto_user.Pass = txtP.Text.Trim(); _dt = _db.DangNhap(ref err, Dto_user); if (_dt.Rows.Count > 0) { if (_dt.Rows[0]["ErrCode"].ToString() == "0") { cls_Main._username = _dt.Rows[0]["ErrUser"].ToString(); this.Hide(); Form1 frmain = new Form1(); frmain.ShowDialog(); } } }