Escaping new-line characters with XmlDocument

问题:

My application generates XML using XmlDocument. Some of the data contains newline and carriage return characters.

When text is assigned to an XmlElement like this:

   e.InnerText = "Hello\nThere";

The resulting XML looks like this:

<e>Hello
There</e>

The receiver of the XML (which I have no control over) treats the new-line as white space and sees the above text as:

 "Hello There"

For the receiver to retain the new-line it requires the encoding to be:

<e>Hello&#xA;There</e>

If the data is applied to an XmlAttribute, the new-line is properly encoded.

I've tried applying text to XmlElement using InnerText and InnerXml but the output is the same for both.

Is there a way to get XmlElement text nodes to output new-lines and carriage-returns in their encoded forms?

Here is some sample code to demonstrate the problem:

string s = "return[\r] newline[\n] special[&<>\"']";
XmlDocument d = new XmlDocument();
d.AppendChild( d.CreateXmlDeclaration( "1.0", null, null ) );
XmlElement  r = d.CreateElement( "root" );
d.AppendChild( r );
XmlElement  e = d.CreateElement( "normal" );
r.AppendChild( e );
XmlAttribute a = d.CreateAttribute( "attribute" );
e.Attributes.Append( a );
a.Value = s;
e.InnerText = s;
s = s
    .Replace( "&" , "&amp;"  )
    .Replace( "<" , "&lt;"   )
    .Replace( ">" , "&gt;"   )
    .Replace( "\"", "&quot;" )
    .Replace( "'" , "&apos;" )
    .Replace( "\r", "&#xD;"  )
    .Replace( "\n", "&#xA;"  )
;
e = d.CreateElement( "encoded" );
r.AppendChild( e );
a = d.CreateAttribute( "attribute" );
e.Attributes.Append( a );
a.InnerXml = s;
e.InnerXml = s;
d.Save( @"C:\Temp\XmlNewLineHandling.xml" );

The output of this program is:

<?xml version="1.0"?>
<root>
  <normal attribute="return[&#xD;] newline[&#xA;] special[&amp;&lt;&gt;&quot;']">return[
] newline[
] special[&amp;&lt;&gt;"']</normal>
  <encoded attribute="return[&#xD;] newline[&#xA;] special[&amp;&lt;&gt;&quot;']">return[
] newline[
] special[&amp;&lt;&gt;"']</encoded>
</root>

Thanks in advance. Chris.

回答1:

How about using HttpUtility.HtmlEncode()?
http://msdn.microsoft.com/en-us/library/73z22y6h.aspx

OK, sorry about the wrong lead there. HttpUtility.HtmlEncode() will not handle the newline issue you're facing.

This blog link will help you out, though
http://weblogs.asp.net/mschwarz/archive/2004/02/16/73675.aspx

Basically, the newline handling is controlled by the xml:space="preserve" attribute.

Sample working code:

XmlDocument doc = new XmlDocument();
doc.LoadXml("<ROOT/>");
doc.DocumentElement.InnerText = "1234\r\n5678";

XmlAttribute e = doc.CreateAttribute(
    "xml", 
    "space", 
    "http://www.w3.org/XML/1998/namespace");
e.Value = "preserve";
doc.DocumentElement.Attributes.Append(e);

var child = doc.CreateElement("CHILD");
child.InnerText = "1234\r\n5678";
doc.DocumentElement.AppendChild(child);

Console.WriteLine(doc.InnerXml);
Console.ReadLine();

The output will read:

<ROOT xml:space="preserve">1234
5678<CHILD>1234
5678</CHILD></ROOT>

回答2:

Encoding is probably your best bet using the methods described here. Or perhaps you could look at using a CData section for your content instead.

回答3:

In .net 2.0 use the XmlDocument PreserveWhitespace switch

XmlDocument d = new XmlDocument();
d.PreserveWhitespace = true;

回答4:

i had the same problem Preserve carriage returns when i write/read from xml file using asp.net

the solution is to replace xml space to html space after html generated i add this

        strHtml = strHtml.Replace("&lt;br/&gt;", "<br/>");

at the end of the method before closing the stream reader