How to insert new item to channel in XML file

I want to insert new element inside <channel> tag using vb code
my xml file looks like :

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:media="http://search.yahoo.com/mrss/">
<channel>

</channel>
</rss>

this is my code :

Dim root = New XElement("item")
Dim title = New XElement("title", New XCData(TextBox3.Text))
Dim link = New XElement("link", TextBox6.Text)
Dim pubDate = New XElement("pubDate", DateTime.Now.ToString("yyy/MM/dd HH:mm"))
Dim description = New XElement("description", New XCData(TextBox5.Text))
Dim thumbnail = New XElement("media.thumbnail",
New XAttribute("url", "http://karary-001-site1.htempurl.com/files/" + attac1 + "?itok=YdFLolAU"),
New XAttribute("height", 266),
New XAttribute("width", 127))
root.Add(title, link, pubDate, description, thumbnail)
document.Root.Add(root)
document.Save(FilePath)

my code add new items after channel and rss tag end !!

That's because you added it to the document.Root node:
document.Root.Add(root)

So it tacked it onto the end. That's not what you want. You need to find the correct node you want to add the new nodes to, and .add to THAT node.

-tg