XML DocumentElement is trashing the innerXml

I have a simple XML file, shown below, which when read-in via a basic XmlDocument.Load(filename.xml). If I load the file, and inspect it's innerXML, it all looks normal. However, when I inspect the value of DocumentElement, it's a mess!!! I kept the example small, so you can easily see there is no mal-formation:

<?xml version="1.0" encoding="UTF-8"?>
<fax:FaxService xmlns:fax="http://www.hp.com/schemas/imaging/con/service/fax/2009/02/11/" xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionar开发者_如何学Cies/1.0/">
  <fax:ServiceDefaults>
    <fax:ServiceSendDefaults>
      <fax:InternetFaxSettings>
        <dd:FaxFileFormat>MTIFFG4</dd:FaxFileFormat>
        <dd:UseEmailAsFaxAcctAddr>false</dd:UseEmailAsFaxAcctAddr>
        <dd:AutoCompleteToNANP>false</dd:AutoCompleteToNANP>
        <dd:RetryInterval>0</dd:RetryInterval>
        <dd:MaxRetryAttempts>0</dd:MaxRetryAttempts>
      </fax:InternetFaxSettings>
    </fax:ServiceSendDefaults>
  </fax:ServiceDefaults>
</fax:FaxService>

Now, try this in C# with this simple code:

...

XmlDocument xDoc = new XmlDocument();
xDoc.Load("*XMLSAMPLE.XML*");

textBox1.Text = xDoc.InnerXml;
textBox2.Text = xDoc.DocumentElement.InnerXml;

...

It's completely mangled, with the 2nd namespace repeated with every dd tag, and not even included in the top-most tag.

What am I doing wrong? This is driving me nuts!

The content returned by xDoc.DocumentElement.InnerXml is semantically identical to your original ServiceDefaults tag - if the first fragment conforms to your XML schema, the InnerXml fragment will also conform to the definition of the inner element. Just because the framework has re-arranged the namespace declarations does not change the semantics of the document.

Compare the output of your the two XmlDocument properties:

xDoc.DocumentElement:

<?xml version="1.0" encoding="UTF-8"?>
   <fax:FaxService xmlns:fax="http://www.hp.com/schemas/imaging/con/service/fax/2009/02/11/" xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">
    <fax:ServiceDefaults>
     <fax:ServiceSendDefaults>
      <fax:InternetFaxSettings>
        <dd:FaxFileFormat>MTIFFG4</dd:FaxFileFormat>
        <dd:UseEmailAsFaxAcctAddr>false</dd:UseEmailAsFaxAcctAddr>
        <dd:AutoCompleteToNANP>false</dd:AutoCompleteToNANP>
        <dd:RetryInterval>0</dd:RetryInterval>
        <dd:MaxRetryAttempts>0</dd:MaxRetryAttempts>
      </fax:InternetFaxSettings>
     </fax:ServiceSendDefaults>
    </fax:ServiceDefaults>
  </fax:FaxService>

xDoc.DocumentElement.InnerXml:

<fax:ServiceDefaults xmlns:fax="http://www.hp.com/schemas/imaging/con/service/fax/2009/02/11/">
  <fax:ServiceSendDefaults>
   <fax:InternetFaxSettings>
     <dd:FaxFileFormat xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">MTIFFG4</dd:FaxFileFormat>
     <dd:UseEmailAsFaxAcctAddr xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">false</dd:UseEmailAsFaxAcctAddr>
     <dd:AutoCompleteToNANP xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">false</dd:AutoCompleteToNANP>
     <dd:RetryInterval xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">0</dd:RetryInterval>
     <dd:MaxRetryAttempts xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">0</dd:MaxRetryAttempts>
   </fax:InternetFaxSettings>
  </fax:ServiceSendDefaults>
 </fax:ServiceDefaults>

A look at the following link in MSDN will help shed light on your situation:
http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.innerxml.aspx

Basically, xDoc.DocumentElement.InnerXml is looking at the <fax:ServiceDefaults> node, whereas xDoc.InnerXml is looking one level higher (FaxService node). This is crucial to understanding your problem - because all of your xmlns is on the FaxService node.

Make the following change to your XML document, and notice what happens (basically, copy over the xmlns info to the ServiceDefaults node:

<?xml version="1.0" encoding="UTF-8"?>
<fax:FaxService xmlns:fax="http://www.hp.com/schemas/imaging/con/service/fax/2009/02/11/" xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">
  <fax:ServiceDefaults xmlns:fax="http://www.hp.com/schemas/imaging/con/service/fax/2009/02/11/" xmlns:dd="http://www.hp.com/schemas/imaging/con/dictionaries/1.0/">
    <fax:ServiceSendDefaults>
      <fax:InternetFaxSettings>
        <dd:FaxFileFormat>MTIFFG4</dd:FaxFileFormat>
        <dd:UseEmailAsFaxAcctAddr>false</dd:UseEmailAsFaxAcctAddr>
        <dd:AutoCompleteToNANP>false</dd:AutoCompleteToNANP>
        <dd:RetryInterval>0</dd:RetryInterval>
        <dd:MaxRetryAttempts>0</dd:MaxRetryAttempts>
      </fax:InternetFaxSettings>
    </fax:ServiceSendDefaults>
  </fax:ServiceDefaults>
</fax:FaxService>

Suddenly your code will behave according to your expectations. So hopefully this helps you towards understanding the issue. What the permanent fix should be, that's up to you.

HTH!