如：
<?xml version="1.0" encoding="GB2312"?>
<res>
<srccity>北京</srccity>
<destcity>上海</destcity>
<date>15NOV</date>
<re>
<direct>1</direct>
<segment>
<fn>CA155</fn>
<src>PEK</src>
<dest>PVG</dest>
<dist>1178</dist>
<depart>07:25</depart>
<arrive>09:35</arrive>
<ptype>738</ptype>
<stops>0</stops>
<price>0</price>
<oilTax>100</oilTax>
<sites />
<qs />
<eticket>1</eticket>
</segment>
</re>
<re>
<direct>1</direct>
<segment>
<fn>MU583</fn>
<src>PEK</src>
<dest>PVG</dest>
<dist>1178</dist>
<depart>11:00</depart>
<arrive>13:15</arrive>
<ptype>320</ptype>
<stops>0</stops>
<price>1130</price>
<oilTax>100</oilTax>
<sites>
<site>
<cw>Y</cw>
<zw>>9</zw>
<p>1130</p>
<zk>1</zk>
<ticketAgents />
<IsPromotion>0</IsPromotion>
<PromotionContentID>0</PromotionContentID>
<Restriction>没有找到匹配的退改签规则</Restriction>
</site>
<site>
<cw>B</cw>
<zw>>9</zw>
<p>1020</p>
<zk>0.9</zk>
<ticketAgents />
<IsPromotion>0</IsPromotion>
<PromotionContentID>0</PromotionContentID>
<Restriction>没有找到匹配的退改签规则</Restriction>
</site>
</sites>
<qs />
<eticket>1</eticket>
</segment>
</re>
一个node下面还有子Node，如何将我想要的内容挑选出来，再填充到DataGrid里呢？
