DataTalbe或者DataSet具有Select功能

DataSet dataSet = new DataSet();
        dataSet.ReadXml(Server.MapPath("~/class.xml"));
        DataTable dt = dataSet.Tables[0];
       DataRow[] dr = dt.Select(" ParentID=17 ", " SortID asc ");

for (int i = 0; i < dr.Length; i++)
        {
            Response.Write(dr[i][0].ToString() + "  ");
            Response.Write(dr[i][1].ToString() + "  ");
            Response.Write(dr[i][2].ToString() + "  ");
            Response.Write(dr[i][3].ToString() + "  <br />");
        }