DTD validation issue - vb.net

Question

I'm using the following code to validate an XML file:
'DTD validation
Dim doc As XmlDocument = New XmlDocument()
Dim dtdDoc As String = ftpPath & "\" & dtdDocument
AppendText(vbCrLf)
Try
doc.Load(fileName)
Catch ex As Exception
AppendText(ex.Message)
ShowFailMessage()
End Try
Dim isXmlValid As Boolean = True
Dim xmlValMsg As New StringBuilder()
Dim sw As New StringWriter()
doc.Save(sw)
doc.Save(fileName)
Dim stream As Stream = New FileStream(fileName, FileMode.Open)
Dim settings As New XmlReaderSettings()
settings.ValidationType = ValidationType.DTD
settings.DtdProcessing = DtdProcessing.Parse
AddHandler settings.ValidationEventHandler, AddressOf ValidationCallBack
Dim r As XmlReader = XmlReader.Create(stream, settings, "R:\ftproot\graphics\" & dtdDocument)
While r.Read()
End While
r.Close()
stream.Close()
stream.Dispose()
Private Shared Sub ValidationCallBack(sender As Object, e As ValidationEventArgs)
AppendText("DTD Validation Error: " & e.Message)
isDTDValidated = False
End Sub
I am getting the following error from this validation code:
"The element 'MarketDate' has invalid child element 'Date'. List of possible elements expected: 'DateFormat'."
Here's the relevant XML:
<MarketDate>
<MarketDateRole>01</MarketDateRole>
<Date>20150202</Date>
</MarketDate>
Here's what's in the DTD:
<!ELEMENT MarketDate (MarketDateRole,DateFormat,Date)>
So 'Date' is a valid child element. I am guessing it's not that Date is invalid but that DateFormat is missing. Am I correct with this assumption?