Encoding

[mortb]

1. How do I determine which encoding a xmldocument or xmlreader uses when
opening a document?
I'm not just talking about the <?xml encoding="utf-8"?attribute, but the
actual encoding of the characters in the underlying stream.

2. How do I make sure that the encoding of my created xmldocument or
xmlwriter is in utf-8?

Thanks!
/mortb

[Bjoern Hoehrmann]

* mortb wrote in microsoft.public.dotnet.xml:

>1. How do I determine which encoding a xmldocument or xmlreader uses when
opening a document?
I'm not just talking about the <?xml encoding="utf-8"?attribute, but the
actual encoding of the characters in the underlying stream.

I am not aware of a property that exposes this information. Note that if
the XML declaration is absent or has no encoding declaration, the actual
encoding is generally assumed to be UTF-8 (exceptions being e.g. if the
document is loaded through some higher level protocol that specifies
other encoding information), and cases where you actually need to know
are very rare.

>2. How do I make sure that the encoding of my created xmldocument or
xmlwriter is in utf-8?

XmlDocument objects are in no character encoding, they only are after
you have serialized them to some byte string like when writing to a
file. As for the various serialization methods, they generally either
have an option to specify the encoding or inherit it in some way. For
example, XmlTextWriter has a constructor that accepts a System.Text.
Encoding object.
--
Björn Höhrmann · mailto:bj****@hoehrmann.de · http://bjoern.hoehrmann.de
Weinh. Str. 22 · Telefon: [phone] · http://www.bjoernsworld.de
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[mortb]

"Bjoern Hoehrmann" <bj****@hoehrmann.dewrote in message
news:h9********************************@hive.bjoer n.hoehrmann.de...

>
I am not aware of a property that exposes this information. Note that if
the XML declaration is absent or has no encoding declaration, the actual
encoding is generally assumed to be UTF-8 (exceptions being e.g. if the
document is loaded through some higher level protocol that specifies
other encoding information), and cases where you actually need to know
are very rare.

The reason I need to know is that there will be text in Asian languages
(e.g. Chineese) in the XML file. In this case encoding is important.

>

>>2. How do I make sure that the encoding of my created xmldocument or
xmlwriter is in utf-8?

XmlDocument objects are in no character encoding, they only are after
you have serialized them to some byte string like when writing to a
file. As for the various serialization methods, they generally either
have an option to specify the encoding or inherit it in some way. For
example, XmlTextWriter has a constructor that accepts a System.Text.
Encoding object.

I'll use this constructor then. Thanks!

cheers,
mortb

[Martin Honnen]

mortb wrote:

1. How do I determine which encoding a xmldocument or xmlreader uses when
opening a document?
I'm not just talking about the <?xml encoding="utf-8"?attribute, but the
actual encoding of the characters in the underlying stream.

I don't understand that question. If the encoding is delcared in the XML
declaration (e.g. <?xml version="1.0" encoding="UTF-8"?>) then the
characters in the underlying stream have to encoded with UTF-8,
otherwise the document is not well-formed.
As for reading out the encoding in the XML declaration, XmlReader allows
it with e.g. NET 2.0 C#

using (XmlReader xmlReader = XmlReader.Create(@"file.xml")) {
if (xmlReader.Read() && xmlReader.NodeType ==
XmlNodeType.XmlDeclaration) {
Console.WriteLine("Declared encoding is: {0}.",
xmlReader.GetAttribute("encoding"));
}
else {
Console.WriteLine("No XML declaration found.");
}
}
That obviously only helps if the XML document has an XML declaration
declaring the encoding. If not the XML is either UTF-8 or UTF-16
encoded, depending on the presence and form of a byte order mark at the
very beginning.

If you are not working with XmlReader but with XmlDocument then you will
also find the XmlDeclaration node in the DOM tree e.g.

XmlDocument xmlDocument = new XmlDocument();
xmlDocument.Load(@"file.xml");
if (xmlDocument.FirstChild.NodeType ==
XmlNodeType.XmlDeclaration) {
XmlDeclaration declaration = xmlDocument.FirstChild as
XmlDeclaration;
Console.WriteLine("Declared encoding is: {0}.",
declaration.Encoding);
}
else {
Console.WriteLine("No XML declaration found.");
}

2. How do I make sure that the encoding of my created xmldocument or
xmlwriter is in utf-8?

As already pointed out, you can specify the encoding to use when
creating the XmlWriter e.g. in .NET 2.0 with the XmlWriterSettings e.g.
XmlWriterSettings writerSettings = new XmlWriterSettings();
writerSettings.Encoding = System.Text.Encoding.UTF8;
using (XmlWriter xmlWriter = XmlWriter.Create(@"file.xml",
writerSettings) {
xmlWriter.WriteStartDocument();
...
}

But UTF-8 is pretty much the default, for instance when the Save method
of an XmlDocument method is being called and there is no XML declaration
or there is one but no encoding is specified then UTF-8 is used.
--

Martin Honnen --- MVP XML
http://JavaScript.FAQTs.com/