Datapath未显示树视图中的正确路径

Question

**<components>
    <part>
        <manufacturer>asus</manufacturer>
        <model>A3-B</model>
    </part>
    <part>
        <manufacturer>intel</manufacturer>
        <model>V5-F</model>
    </part>
</components>**

这是我为其创建树视图的xml。我通过treeview.selectednode.datapath访问该值。问题是，即使我点击第二部分，每次只显示第一部分的细节。我该如何解决这个问题？

编辑： 这是c代码：

protected void btnSelectFile_Click(object sender, EventArgs e)
    {
          LoadXMLTree("~/first.xml");  
    }

private void LoadXMLTree(string fileName)
    {
        try
        {
            xmlDataSource.DataFile = fileName;
            xmlDataSource.EnableCaching = false;
            xmlTreeView.DataSourceID = "xmlDataSource";
            xmlTreeView.DataBind();
        }
        catch (Exception ex)
        {
            lblMessage.Text = "Exception: " + ex.Message;
        }
    }

protected void xmlTreeView_SelectedNodeChanged(object sender, EventArgs e)
    {
        XmlDocument doc = new XmlDocument();
        doc.Load("~/first.xml");
        XmlNode node = 
                    doc.SelectSingleNode(xmlTreeView.SelectedNode.DataPath);
        txtEditXML.Text = node.InnerXml;
        Session["CurrentEditXpath"] = xmlTreeView.SelectedNode.DataPath;
    }