Parsing code document with header and footer set

Hi,

I'm trying to parse some VB code using the following extension method, but it fails with errors regarding imports section:

public static IParseData Parse(this ISyntaxLanguage language, string header, string body, string footer)
{
  language.ThrowArgumentNullException("language");
  var parser = language.GetParser();
  if (parser == null)
  {
    returnnull;
  }
  var codeDocument = newCodeDocument { Language = language };
  codeDocument.SetHeaderAndFooterText(header, footer);
  codeDocument.SetText(body);
  var snapshot = codeDocument.CurrentSnapshot;
  var reader = snapshot.GetReader(0); // should this be: -snapshot.HeaderText.Length?
  var parseRequest = newParseRequest(Guid.NewGuid().ToString(), reader.BufferReader, language, codeDocument) { Snapshot = snapshot };
  return parser.Parse(parseRequest);
}

 The header is:

Public Partial Class MyClass

The body:

Sub MySub

End Sub

And the footer

End Class

I think it is failing because it does not consider the header when parsing the code.  When the syntax editor returns the parse result for the same VB code, I note the snapshot start point is -27 and the EndPoint is larger than the snapshot I get from the code above.  Is there some way to create a new snapshot for document or to modify the current one to use the header and footer?

Thanks in advance,

Nick