Where are these strange characters coming from?

:wave:
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:

Code:

---

        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:

Code:

---

                            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?

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

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.

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:

Code:

---

                            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.

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

Code:

---

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

---

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