[2005] How to construct a valid "xpath"?

[MikeLI]

I have a DOM tree (xmlCOA).
It is associated with a TreeView (TreeView1).
I would like to add a new node to the DOM tree.
After I construct the new node, I locate a particular node for adding the new node as its child.
I use "fullPath" to construct the xpath to locate the targeted node.
But, I don't understand something: the fullPath return: #document/.......
Should I trim the "#document" away?
No matter I cut it or not, it causes error: wrong xpath expression.
Why?



visual basic code:--------------------------------------------------------------------------------

Private Sub btnCreate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCreate.Click
        'construct the new node
        Dim newNode As xmlFile.XmlNode = _
                xmlCOA.CreateNode(Xml.XmlNodeType.Element, "",  txtElementName.Text, "")
        newNode.InnerText() = txtItemName.Text
 
        'construct the xpath 
        Dim txt As String = TreeView1.SelectedNode.Text
        Dim fullPath As String = TreeView1.SelectedNode.FullPath 'return value is: #document/.......
        fullPath = fullPath.substring(9) 'cut "#document"
 
        'this is valid, but it cannot locate the exact node
        'Dim xn As xmlFile.XmlNode = xmlCOA.SelectSingleNode("//" + txt)
 
        'error: xpath is not valid
        Dim xn As xmlFile.XmlNode = xmlCOA.SelectSingleNode(fullpath)
 
        xn.AppendChild(newNode)
    End Sub