xml 提取排序的问题？有高手可以给个详细思路解决吗？

<Item>
<Url>m0/w23/h80/4106b72a5a.0.html </Url>
<EngineWeight>0.002169 </EngineWeight>
<ComIp>3741344522 </ComIp>
</Item>
<Item>
<Url>h80/4106b72a5a.0.html </Url>
<EngineWeight>0.069 </EngineWeight>
<ComIp>1323423423 </ComIp>
</Item>

如何处理这样的XML 根据 <EngineWeight> 内值进行排序 使得结果为从大到小排列
结果应为：  即engineweight0.069 > 0.002169
<Item>
<Url>h80/4106b72a5a.0.html </Url>
<EngineWeight>0.069 </EngineWeight>
<ComIp>1323423423 </ComIp>
</Item>
<Item>
<Url>m0/w23/h80/4106b72a5a.0.html </Url>
<EngineWeight>0.002169 </EngineWeight>
<ComIp>3741344522 </ComIp>
</Item>