XMLwriter help

[aj123]

Helloo all
am using xmltextWriter to write node in xml file
XmltextWriter w=null
w=new Xmltextwriter(-----);
but the problem not in using writer
the problem is
I have listbox have this values
Level1
Level2
Level2
Level2
Level3
Level3
Level1
Level2
Level3
Level4
Level2
Level2
Level1

and soon on
i want to make witer get values for list and write it to xml
every level1 present base node() and sublevels is subnodes
i want be unlimeted level
xml file show be appear like this
<root>
<level1>
<level2/>
<level2/>
<level2>
<level3/>
<level3/>
</level2>
</level1>

<level1>
<level2>
<level3>
<level4/>
</level3>
</level2>
</level2>
</level2>
</level1>

</root>