title: How to insert new item to channel in xml file
body: <p>I want modify an existing xml file to insert new element inside the Channel using vb code 
  my xml file looks like :</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;rss version="2.0" xmlns:media="http://search.yahoo.com/mrss/"&gt;
  &lt;channel&gt;
  &lt;title&gt;Latest News from Science Magazine&lt;/title&gt;
  &lt;link&gt;http://www.sciencemag.org/rss/news_current.xml&lt;/link&gt;
  &lt;description&gt;Editable in modal at Format : RSS Feed | Settings : RSS Description&lt;/description&gt;
  &lt;pubDate&gt;Wed, 25 Jul 2018 09:10:28 -0400&lt;/pubDate
  
  &lt;item&gt;
    &lt;title&gt;&lt;![CDATA[this is title]]&gt;&lt;/title&gt;
    &lt;link&gt;http://karary-001-site1.htempurl.com&lt;/link&gt;
    &lt;pubDate&gt;2018/07/26 06:29&lt;/pubDate&gt;
    &lt;description&gt;&lt;![CDATA[this id desc]]&gt;&lt;/description&gt;
    &lt;media.thumbnail url="http://karary.com" height="266" width="127" /&gt;
  &lt;/item&gt;
  
  &lt;/channel&gt;
  &lt;/rss&gt;
  </code></pre>
  
  <p>this is my code :</p>
  
  <pre><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)
  </code></pre>
  
  <p>my code add new items after channel and rss tag end !!</p>