System.Data.DataSet.ReadXml C# (CSharp) Method

        public XmlReadMode ReadXml(Stream stream)
        {
            if (stream == null)
            {
                return XmlReadMode.Auto;
            }

            XmlTextReader xr = new XmlTextReader(stream);

            // Prevent Dtd entity in dataset 
            xr.XmlResolver = null;

            return ReadXml(xr, false);
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            DataSet ds = new DataSet();
            DataSet ds1 = new DataSet();
            ds.ReadXml(@"D:\Books.xml");

            bookgrd.DataSource = ds.Tables[0];
            bookgrd.DataBind();

            IEnumerable<DataRow> tbl1row = ds.Tables[0].AsEnumerable();
            ds1.ReadXml(@"D:\Books2.xml");

            IEnumerable<DataRow> tbl2row = ds1.Tables[0].AsEnumerable();
            GridView1.DataSource = ds1.Tables[0];
            GridView1.DataBind();

            var items = tbl2row.AsEnumerable().Select(r => r.Field<string>("id"))
            .Except(tbl1row.AsEnumerable().Select(r => r.Field<string>("id")));

            DataTable TableC = (from row in tbl2row.AsEnumerable()
                                join id in items
                                on row.Field<string>("id") equals id
                                select row).CopyToDataTable();

            GridView2.DataSource = TableC;
            GridView2.DataBind();
        }