<class>
  <student>
    <no>1</no>
    <name>Ann</name>
    <sex>female</sex>
    <age>15</age>
    <score>90</score>
  </student>
  <student>
    <no>2</no>
    <name>Bob</name>
    <sex>male</sex>
    <age>16</age>
    <score>80</score>
  </student>
  <student>
    ……
  </student>
  <student>
    ……
  </student>

</class>

        string strXml = @"<class>
  <student>
    <no>1</no>
    <name>Ann</name>
    <sex>female</sex>
    <age>15</age>
    <score>90</score>
  </student>
  <student>
    <no>2</no>
    <name>Bob</name>
    <sex>male</sex>
    <age>16</age>
    <score>80</score>
  </student>
  <student>    
<no>3</no>
    <name>ttt</name>
    <sex>j</sex>
    <age>15</age>
    <score>92</score>
  </student>
  <student>   
  </student>
</class>";

        XmlDocument xdoc = new XmlDocument();
        xdoc.LoadXml(strXml);

        string strXPath = string.Empty;

        strXPath = "/class/student[score>=90]";
        XmlNodeList oXmlNodes = xdoc.SelectNodes(strXPath);

        foreach (XmlNode node in oXmlNodes)
        {
            string strName = node.SelectSingleNode("/class/student/name").InnerText ;
        }

------解决方案--------------------
应该是不可以的。就像冰箱里有N多瓶饮料，你能否不开冰箱就喝到其中的一瓶呢。