Reading contents of XML file without having to remove the XML declaration

Question

I want to read all XML contents from a file. The code below only works when the XML declaration (<?xml version="1.0" encoding="UTF-8"?>) is removed. What is the best way to read the file without removing the XML declaration?

XmlTextReader reader = new XmlTextReader(@"c:\my path\a.xml");
            reader.Read();
            string rs = reader.ReadOuterXml();

Without removing the XML declaration, reader.ReadOuterXml() returns an empty string.

<?xml version="1.0" encoding="UTF-8"?>  
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing">
  <s:Header>
    <a:Action s:mustUnderstand="1">http://www.as.com/ver/ver.IClaimver/Car</a:Action>
    <a:MessageID>urn:uuid:b22149b6-2e70-46aa-8b01-c2841c70c1c7</a:MessageID>
    <ActivityId CorrelationId="16b385f3-34bd-45ff-ad13-8652baeaeb8a" xmlns="http://schemas.microsoft.com/2004/09/ServiceModel/Diagnostics">04eb5b59-cd42-47c6-a946-d840a6cde42b</ActivityId>
    <a:ReplyTo>
      <a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
    </a:ReplyTo>
    <a:To s:mustUnderstand="1">http://localhost/ver.Web/ver2011.svc</a:To>
  </s:Header>
  <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <Car xmlns="http://www.as.com/ver">
      <carApplication>
        <HB_Base xsi:type="HB" xmlns="urn:core">
          <Header>
            <Advisor>
              <AdvisorLocalAuthorityCode>11</AdvisorLocalAuthorityCode>
              <AdvisorType>1</AdvisorType>
            </Advisor>
          </Header>
          <General>
            <ApplyForHB>yes</ApplyForHB>
            <ApplyForCTB>yes</ApplyForCTB>
            <ApplyForFSL>yes</ApplyForFSL>
            <ConsentSupplied>no</ConsentSupplied>
            <SupportingDocumentsSupplied>no</SupportingDocumentsSupplied>
          </General>
        </HB_Base>
      </carApplication>
    </Car>
  </s:Body>
</s:Envelope>

Update

I know other methods that use NON-xml reader (e.g. by using File.ReadAllText()). But I need to know a way that uses an xml method.

Is "remove this..." bit part of the document, or part of your question? — Jon Hanna, Dec 16 '11 at 20:22
Sorry for the confusion. it is the comment, not for testing. Please refer to the updated contents. — Pingpong, Dec 16 '11 at 20:28
Is the file *actually* encoded in UTF-8? What error do you get if you don't remove that? — Jon Skeet, Dec 16 '11 at 20:42
Jon, Without removing the declaration element, reader.ReadOuterXml() return empty string. — Pingpong, Dec 16 '11 at 20:44
Don't use `new XmlTextReader()`. I thought sure I had mentioned that to you. Use `XmlReader.Create()` instead. — John Saunders, Dec 17 '11 at 01:30

dthorpe · Accepted Answer · 2011-12-17T06:16:56.647

There can be no text or whitespace before the <?xml ?> encoding declaration other than a BOM, and no text between the declaration and the root element other than line break.

Anything else is an invalid document.

UPDATE:

I think your expectation of XmlTextReader.read() is incorrect.

Each call to XmlTextReader.Read() steps through the next "token" in the XML document, one token at a time. "Token" means XML elements, whitespace, text, and XML encoding declaration.

Your call to reader.ReadOuterXML() is returning an empty string because the first token in your XML file is an XML declaration, and an XML declaration does not have an OuterXML.

Consider this code:

    XmlTextReader reader = new XmlTextReader("test.xml");
    reader.Read();
    Console.WriteLine(reader.NodeType);  // XMLDeclaration
    reader.Read();
    Console.WriteLine(reader.NodeType);  // Whitespace
    reader.Read();
    Console.WriteLine(reader.NodeType);  // Element
    string rs = reader.ReadOuterXml();

The code above produces this output:

XmlDeclaration
Whitespace
Element

The first "token" is the XML declaration.

The second "token" encountered is the line break after the XML declaration.

The third "token" encountered is the <s:Envelope> element. From here a call to reader.ReadOuterXML() will return what I think you're expecting to see - the text of <s:Envelope> element, which is the entire soap packet.

If what you really want is to load the XML file into memory as objects, just call var doc = XDocument.Load("test.xml") and be done with the parsing in one fell swoop.

Unless you're working with an XML doc that is so monstrously huge that it won't fit in system memory, there's really not a lot of reason to go poking through the XML document one token at a time.

Thanks. your answer is very helpful. I wonder a line break or white space between them is still considered a token, which seems not necessary. — Pingpong, Dec 17 '11 at 06:46
Treating whitespace (and comments) as a token is important to preserve the line breaks and indents that users use to format the XML code. Without that, you would constantly be fighting with your XML editor as it reformats your XML and destroys your indent style. If you are not working in a round-trip user interactive manner, just straight processing of XML, you can ignore whitespace and comments. But you have to actively ignore them. ;> — dthorpe, Dec 17 '11 at 07:54

score 2 · Answer 2 · answered Dec 16 '11 at 19:09

What about

XmlDocument doc=new XmlDocument;
doc.Load(@"c:\my path\a.xml");
//Now we have the XML document - convert it to a String
//There are many ways to do this, one should be:
StringWriter sw=new StringWriter();
doc.Save(sw);
String finalresult=sw.ToString();

score 1 · Answer 3 · answered Dec 16 '11 at 19:05

1

EDIT: I'm assuming you mean you actually have text between the document declaration and the root element. If that's not the case, please clarify.

Without removing the extra text, it's simply an invalid XML file. I wouldn't expect it to work. You don't have an XML file - you have something a bit like an XML file, but with extraneous stuff before the root element.

answered Dec 16 '11 at 19:05

Jon Skeet

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Sorry for the confusion. it is the comment, not for testing. Please refer to the updated contents. – Pingpong Dec 16 '11 at 20:28

score 0 · Answer 4 · answered Dec 16 '11 at 19:09

0

IMHO you can't read this file. It's because there's a plain text before the root element <s:Envelope> which makes whole document invalid.

answered Dec 16 '11 at 19:09

Wojteq

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Sorry for the confusion. it is the comment, not for testing. Please refer to the updated contents. – Pingpong Dec 16 '11 at 20:28

score 0 · Answer 5 · answered Dec 16 '11 at 19:12

You're parsing an XML document as XML just to obtain the source text? Why?

If you really want to do that then:

string rs;
using(var rdr = new StreamReader(@"c:\my path\a.xml"))
  rs = rdr.ReadToEnd();

Will work, but I'm really not sure that is what you actually want. This pretty much ignores that it's XML and just reads the text. Useful for some things, but not a lot.

Reading contents of XML file without having to remove the XML declaration

5 Answers5