Xmltextwriter Open And Closing

I am using the xmltextwriter and having issues with opening tags not showing if the field is blank here is the start of my code

Code:
Dim strFilePath As String = Server.MapPath("../test.xml")
Dim utf8 As Encoding = New UTF8Encoding(False)
Dim objWriter As XmlTextWriter = New XmlTextWriter(strFilePath, New UTF8Encoding(False))
' start writing the XML document
objWriter.WriteStartDocument()
Try
conn.Open()
myreader = cmd.ExecuteReader
objWriter.WriteStartElement("testfile")
While myreader.Read
output the first "product" element
objWriter.WriteStartElement("product", Nothing)
objWriter.WriteElementString("Id", myreader("rvid").ToString)
objWriter.WriteElementString("Class", myreader("RVClass").ToString)
objWriter.WriteElementString("Manu", myreader("rvmanu").ToString)
objWriter.WriteElementString("Model", myreader("rvmake") & " " & myreader("rvmodel"))
objWriter.WriteElementString("Year", myreader("rvyear").ToString)
objWriter.WriteElementString("Price", myreader("rvcashprice").ToString)
objWriter.WriteElementString("NU", myreader("rvnu").ToString)
objWriter.WriteElementString("SCapacity", myreader("rvcapacity").ToString)
objWriter.WriteElementString("Fuel", myreader("rvfuel").ToString)
objWriter.WriteElementString("Length", myreader("rvlenft").ToString)
objWriter.WriteElementString("Air", myreader("rvair").ToString)
objWriter.WriteElementString("Awnings", myreader("rvawnings").ToString)

Thats not all of it.. but what happens is if it is blank value Then i get this, as you see fuel has no opening tags, and the company i am supplying to needs these.

<Price>0.0000</Price>
<NU>U</NU>
<SCapacity>0</SCapacity>
<Fuel />
<Length>0</Length>

What can i do to make this work how i want? I though the .tostring woudl fix it but it didnt.