xml文件？
怎样获取xml文件中总共有多少个不同的节点数
如：

XML code

<?xml version="1.0" encoding="utf-8"?><School sname="aa">  <Class cname="c1">    <Student name="bb" age="21">    </Student>    <Stu name="stu1" />  </Class>  <Class cname="c2">    <Student name="cc" age="22">    </Student>  </Class></School>

C# code

public List<string> count_list = new List<string>();            public void GetNodeName(XmlNode xn)            {                string name = xn.Name;                if (!count_list.Contains(name))                    count_list.Add(name);                if (xn.HasChildNodes)                {                    foreach (XmlNode temp in xn.ChildNodes)                    {                        GetNodeName(temp);                    }                }            }