How to save Dataset values in Xml

DataSet ds = new DataSet();
           string connectionString = ConfigurationManager.ConnectionStrings["InvoiceConnectionString"].ConnectionString;
           SqlConnection conn = new SqlConnection(connectionString);
           string selectSql = "Select CompName,CompAdd,Tel,Fax,SalesPerson from CustomerDetails Where CusId =@cusid";
           SqlDataAdapter da = new SqlDataAdapter(selectSql, conn);
           da.SelectCommand.Parameters.AddWithValue("@cusid", cid);

           da.Fill(ds, "shipto");
           dv2.DataSource = ds.Tables["shipto"];