Where are these strange characters coming from?

[dolot]

So I have the following code that uses and xsl file to transform an xml file to html and outputs it to a memory stream:

        Public Shared Function GetTransformedHTML(ByVal PesXmlDoc As Xml.XmlDocument, ByVal TransformFile As String) As IO.MemoryStream

            'create an XSL transformation
            Dim Transform As New System.Xml.Xsl.XslCompiledTransform
            Transform.Load(AppFramework.Configuration.ConfigFiles.GetConfigurationFileFullName(TransformFile))

            'perform the transform to an html file in the temp folder
            Dim OutStream As New IO.MemoryStream
            Transform.Transform(PesXmlDoc, Nothing, OutStream)
            Return OutStream

        End Function

Then, I output the memory stream to a file using the following:

                            Dim Writer As New IO.StreamWriter(OutputFileName)
                            Dim Buffer As Byte() = HtmlStream.GetBuffer
                            For I As Integer = 0 To Buffer.Length - 1
                                Writer.Write(Chr((Buffer(I))))
                            Next
                            Writer.Close()

It works great, except for one wrinkle. The first three characters in the file are "". They aren't in the xsl document nor in the xml document - near as I can tell. Where in the world did they come from?

I can hack my way around it by simply skipping the first 3 bytes of the memory stream, but that seems dangerous. What if 'in the wild' those first 3 characters aren't there, or maybe there will be 5, or maybe they will be somewhere else?

Any ideas anyone?

[zdavis]

Have you tried opening this file in say notepad?

Might try using a StreamReader to read it as a text file and see if there are any bad characters in there.

If there aren't any then my best guess would be something is get messed up in load method.

-zd

[dolot]

Yeah, I think my next test will be to write it to a StreamWriter instead of a MemoryStream in the function that transforms the xml - just as a test to see if the strange characters are coming out of the transformation or are tied to the memorystream somehow.

[dolot]

So my next test was actually to pass the memory stream to a 3rd party tool we have that converts html to pdf. That worked fine. So then I wondered if there wasn't something about the buffer that was causing the problem, so I changed the second block of code above to look like this:

                            HtmlStream.Position = 0
                            Dim R As New IO.StreamReader(HtmlStream)
                            Dim W As New IO.StreamWriter(OutputFileName)
                            W.Write(R.ReadToEnd)
                            W.Close()

This works fine. So what I'm guessing is that those first few strange characters were some sort of buffer definition bytes. When I just read the stream, those aren't being included.

Anyway, problem solved - but if anybody has any insight into what's going on under the hood I'd be interested to hear.

[Serge]

These weird 3 characters are the UTF-8 BOM, which is actually discouraged by the Unicode standard. You may disable it using:

var sw = new IO.StreamWriter(path, new System.Text.UTF8Encoding(false));
doc.Save(sw);
sw.Close();

[dolot]

Aha! I knew that had to be some explanation. Thanks.