How to refresh Radgrid [Resolved]

Hi Guru
I put Radgird and button into page when user clikc button radgrid display data that select from sql (not use SqlDataSource control) .
I have problem when user click page number 2 radgrid disble but repeated click button radgrid show data page2

help me please
thank you

protected void btnSearch_Click(object sender, EventArgs e)
    {
        string conStr = ConfigurationManager.ConnectionStrings["DCDBStr"].ToString();
        SqlConnection myCon = new SqlConnection(conStr);
        myCon.Open();
        string sqlStr = string.Format("SELECT o.SOID,o.PONO,o.ShipTo,s.ShipToName,o.MaterialCode,m.MaterialName,o.Quantity,m.Units FROM ServiceOrders o LEFT JOIN Materials m ON m.MaterialCode = o.MaterialCode LEFT JOIN ShipToParty s ON s.ShipTo=o.ShipTo WHERE PONO='{0}'", txtPONO.Text);
        SqlDataAdapter da = new SqlDataAdapter(sqlStr, myCon);
        DataSet ds = new DataSet();
        da.Fill(ds, "x");
        DataTable dt = ds.Tables["x"];
        if (dt.Rows.Count > 0)
        {
            RadGrid1.DataSource = dt;
            RadGrid1.DataBind();
        }
        else
        {
            RadAjaxManager1.Alert("No Invoice");
        }
       
    }

[Resolved]