参考文章：http://chs.gotdotnet.com/quickstart/howto/doc/Xml/XmlNameSpace.aspx

偶的源码：
publicvoidbindXml(stringxmlUrl)
{
System.Xml.XmlDocumentdoc=newSystem.Xml.XmlDocument();
doc.Load(System.AppDomain.CurrentDomain.BaseDirectory+"kkjj.xml");
//doc.Load(xmlUrl);
doc.SelectNodes("/rss/channel");
System.Xml.XmlNoderoot=doc.DocumentElement;
System.Xml.XmlNodexn=root.SelectSingleNode("/rss/channel");
outStr+="相册名称："+xn.SelectSingleNode("title").InnerText;//相册名称
outStr+="<br>相册url："+xn.SelectSingleNode("link").InnerText;//相册url
outStr+="<br>相册图片：<imgsrc='"+xn.SelectSingleNode("image/url").InnerText+"'/>";//相册首页图片

//outStr+="<br><imgsrc='"+xn.SelectNodes("item")[0].SelectSingleNode("enclosure").Value+"'>";
System.Xml.XmlNodeListxnl=xn.SelectNodes("item");
outStr+="<br>相册图片数："+xnl.Count.ToString()+"张";

System.Xml.XmlNamespaceManagernsmanager=newSystem.Xml.XmlNamespaceManager(doc.NameTable);
nsmanager.AddNamespace("media","http://search.yahoo.com/mrss/");

//创建包含XPATH表达式的字符串以进行计算。
stringexprString=String.Format("//{0}:group","media");

System.Xml.XmlNodeListnodelist=doc.SelectNodes(exprString,nsmanager);

outStr+="<br>media:title:"+nodelist[0].SelectSingleNode("media:title",nsmanager).Attributes["type"].InnerText;





//for(inti=0;i<xnl.Count;i++)
//{
//outStr+="<br><imgsrc='"+xnl[i].SelectSingleNode("enclosure").Attributes["url"].InnerText+"'/>";
//}
}

当时看到了。。gg的xml里面有冒号，就卡卡解决了。。
付上xml片段

-<media:group>
<media:titletype="plain">02.JPG</media:title>
<media:descriptiontype="plain"/>
<media:keywords/>
<media:thumbnailurl="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/s72/02.JPG"height="48"width="72"/>
<media:thumbnailurl="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/s144/02.JPG"height="96"width="144"/>
<media:thumbnailurl="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/s288/02.JPG"height="192"width="288"/>
<media:contenturl="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/02.JPG"height="400"width="600"type="image/jpeg"medium="image"/>
<media:credit>成刚</media:credit>
</media:group>

xml地址：http://picasaweb.google.com/pengpengsay/lNFxFK