How to create a Xml Document from a fully escaped Xml string? - c#

Question Background:
I have an XML response from a web service (that I am unable to control the content of) that I would like to validate. For example, often the response will have a URL in it that has query string parameters using a "&".
Code:
The following code gives an example of escaping an XML string with illegal characters. This will indeed produce an escaped string:
string xml = "<node>it's my \"node\" & i like it<node>";
string encodedXml = System.Security.SecurityElement.Escape(xml);
// RESULT: <node>it&apos;s my "node" & i like it<node>
If I know attempt to load this escaped XML into a new Xml Document, I will receive an error that the first character of the XML is not valid:
var doc = new XmlDocument();
// Error will occur here.
doc.LoadXml(encodedXml);
Error output:
Data at the root level is invalid. Line 1, position 1.
How do I load this escaped XML into an XML Document object?

This is not a valid XML document:
<node>it&apos;s my "node" & i like it<node>
When you escape the angle brackets on the tags, they are no longer treated as tags by the XML parser. It's all just text in an element -- but there's no element containing it. In XML, there must be a root element. That's a requirement. It may be an arbitrary requirement, and that may be unjust, but you'll never win an argument with a parser.
What you're doing is like giving this to a C# compiler:
string s = \"foo\" bar\";
The outer quotes shouldn't be escaped.
This is what you want:
string xml = "<node>it&apos;s my "node" & i like it</node>";
Note also that your original XML was broken already:
string xml = "<node>it's my \"node\" & i like it<node>";
Your "closing" tag isn't a closing tag. It should be </node>, not <node>.

If you are receiving a response from another web application / API / service, it is likely that the contents are Html encoded.
Take a look at the WebUtility class, particularly, HtmlDecode and UrlDecode. This is likely to convert your "string" data to proper Xml.

If you're receiving valid XML back from the service you can convert the response using something like this:
//...
WebResponse response = request.GetResponse();
XDocument doc = XDocument.Parse
((
new System.IO.StreamReader
(
response.GetResponseStream()
)
).ReadToEnd());
If you're receiving invalid XML from a service which should return valid XML, contact whoever owns/provides that service / raise a support ticket with them in the appropriate way.
Any other action is a hack. Sometimes that may be required (e.g. when you're dealing with a legacy system that's no longer supported with bugs that have never been corrected), but pursue the non-hacky routes first.

Related

invalid characters in xml c#

I am trying to parse the below with in C# with xmldocument. but I can't load it. It says invalid characters. Even in the browser it doesn't display correctly complaining about invalid characters. I need to loop through all elements in this string.
Can someone please advise what's wrong here?
<div><b>Q1.
What is your name?:</b> BTB (Build the bank)</div>
<div><b>Q2.
How old are you?:</b> 29</div>
code is this:
XmlDocument xml = new XmlDocument();
xml.Load(item.Summary);
error is: "Illegal characters in path."
XmlDocument.Load expects a file name to load the xml from. Try LoadXml.
"BTB (Build the bank)" needs to be wrapped in its own tag if this shall be a valid xml. It is valid html though.
Also, xml must have a single top node.

Handling \x01 received from Flash's ExternalInterface

I'm receiving data from a Flash component embedded in a Windows Form. Unfortunately, if the data returned from the socket contains any of the following characters, the call to loadXml below fails:
This is the callback method I have to receive data from the socket (via ExternalInterface in the Flash component).
private void player_FlashCall(object sender, _IShockwaveFlashEvents_FlashCallEvent e)
{
String output = e.request;
//output = CleanInvalidXmlChars(output);
XmlDocument document = new XmlDocument();
document.LoadXml(output);
XmlAttributeCollection attributes = document.FirstChild.Attributes;
String command = attributes.Item(0).InnerText;
XmlNodeList list = document.GetElementsByTagName("arguments");
process(list[0].InnerText);
I had a method to replace the characters with text (CleanInvalidXmlChars), but I don't think this is the right approach.
How can I load this data into an XML file, as this makes separating the method name, paramter names and parameter types which are returned very easy to work with.
Would appreciate any help at all.
Thanks.
If the “XML” contains any U+0001 (aka '\x01') or other similar characters, it is not a valid XML. There is no way you can include those characters in XML (well, in XML 1.0, anyway). See the XML specification. If you need to pass e.g. binary data in XML, you need to convert them to a proper form, e.g. using Base-64.
If the data does contain those invalid characters, it is not XML, and therefore cannot be read using standard XML tools (I don’t think any of the standard .NET classes allows you to override that behavior). You can either replace all those characters (these are basically all control characters (U+0000 through U+001F) except U+0009 (tab), U+000A and U+000D (CR+LF), plus U+FFFE and U+FFFF (noncharacters)) prior to use as you tried – you could devise a safe transformation which would not lose any data (e.g. first replace all # characters with #0040, then replace any invalid character with #xxxx where xxxx is its code, and when processing the parsed XML data, replace all #xxxx back).
Another option is to drop the XML idea and just process it as a string. Just for inspiration, see e.g. this piece of code.

Loading XML to an XDocument with a URL containing an ampersand

XDocument xd = XDocument.Load("http://www.google.com/ig/api?weather=vilnius&hl=lt");
The ampersand & isn't a supported character in a string containing a URL when calling the Load() method. This error occurs:
XmlException was unhandled: Invalid character in the given encoding
How can you load XML from a URL into an XDocument where the URL has an ampersand in the querystring?
You need to URL-encode it as &:
XDocument xd = XDocument.Load(
"http://www.google.com/ig/api?weather=vilnius&hl=lt");
You might be able to get away with using WebUtility.HtmlEncode to perform this conversion automatically; however, be careful that this is not the intended use of that method.
Edit: The real issue here has nothing to do with the ampersand, but with the way Google is encoding the XML document using a custom encoding and failing to declare it. (Ampersands only need to be encoded when they occur within special contexts, such as the <a href="…" /> element of (X)HTML. Read Ampersands (&'s) in URLs for a quick explanation.)
Since the XML declaration does not specify the encoding, XDocument.Load is internally falling back to default UTF-8 encoding as required by XML specification, which is incompatible with the actual data.
To circumvent this issue, you can fetch the raw data and decode it manually using the sample below. I don’t know whether the encoding really is Windows-1252, so you might need to experiment a bit with other encodings.
string url = "http://www.google.com/ig/api?weather=vilnius&hl=lt";
byte[] data;
using (WebClient webClient = new WebClient())
data = webClient.DownloadData(url);
string str = Encoding.GetEncoding("Windows-1252").GetString(data);
XDocument xd = XDocument.Parse(str);
There is nothing wrong with your code - it is perfectly OK to have & in the query string, and it is how separate parameters are defined.
When you look at the error you'll see that it fails to load XML, not to query it from the Url:
XmlException: Invalid character in the given encoding. Line 1, position 473
which clearly points outside of your query string.
The problem could be "Apsiniaukę" (notice last character) in the XML response...
instead of "&" use "&" or "&" . and it will work fine .

How do I stop XElement.Save from escaping characters?

I'm populating an XElement with information and writing it to an xml file using the XElement.Save(path) method. At some point, certain characters in the resulting file are being escaped - for example, > becomes >.
This behaviour is unacceptable, since I need to store information in the XML that includes the > character as part of a password. How can I write the 'raw' content of my XElement object to XML without having these escaped?
Lack of this behavior is unacceptable.
A standalone unescaped > is invalid XML.
XElement is designed to produce valid XML.
If you want to get the unescaped content of the element, use the Value property.
The XML specification usually allows > to appear unescaped. XDocument plays it safe and escapes it although it appears in places where the escaping is not strictly required.
You can do a replace on the generated XML. Be aware per http://www.w3.org/TR/REC-xml#syntax, if this results in any ]]> sequences, the XML will not conform to the XML specification. Moreover, XDocument.Parse will actually reject such XML with the error "']]>' is not allowed in character data.".
XDocument doc = XDocument.Parse("<test>Test>Data</test>");
// Don't use this if it could result in any ]]> sequences!
string s = doc.ToString().Replace(">", ">");
System.IO.File.WriteAllText(#"c:\path\test.xml", s);
In consideration that any spec-compliant XML parser must support >, I'd highly recommend fixing the code that is processing the XML output of your program.

How do I work with an XML tag within a string?

I'm working in Microsoft Visual C# 2008 Express.
Let's say I have a string and the contents of the string is: "This is my <myTag myTagAttrib="colorize">awesome</myTag> string."
I'm telling myself that I want to do something to the word "awesome" - possibly call a function that does something called "colorize".
What is the best way in C# to go about detecting that this tag exists and getting that attribute? I've worked a little with XElements and such in C#, but mostly to do with reading in and out XML files.
Thanks!
-Adeena
Another solution:
var myString = "This is my <myTag myTagAttrib='colorize'>awesome</myTag> string.";
try
{
var document = XDocument.Parse("<root>" + myString + "</root>");
var matches = ((System.Collections.IEnumerable)document.XPathEvaluate("myTag|myTag2")).Cast<XElement>();
foreach (var element in matches)
{
switch (element.Name.ToString())
{
case "myTag":
//do something with myTag like lookup attribute values and call other methods
break;
case "myTag2":
//do something else with myTag2
break;
}
}
}
catch (Exception e)
{
//string was not not well formed xml
}
I also took into account your comment to Dabblernl where you want parse multiple attributes on multiple elements.
You can extract the XML with a regular expression, load the extracted xml string in a XElement and go from there:
string text=#"This is my<myTag myTagAttrib='colorize'>awesome</myTag> text.";
Match match=Regex.Match(text,#"(<MyTag.*</MyTag>)");
string xml=match.Captures[0].Value;
XElement element=XElement.Parse(xml);
XAttribute attribute=element.Attribute("myTagAttrib");
if(attribute.Value=="colorize") DoSomethingWith(element.Value);// Value=awesome
This code will throw an exception if no MyTag element was found, but that can be remedied by inserting a line of:
if(match.Captures.Count!=0)
{...}
It gets even more interesting if the string could hold more than just the MyTag Tag...
I'm a little confused about your example, because you switch between the string (text content), tags, and attributes. But I think what you want is XPath.
So if your XML stream looks like this:
<adeena/><parent><child x="this is my awesome string">This is another awesome string<child/><adeena/>
You'd use an XPath expression that looks like this to find the attribute:
//child/#x
and one like this to find the text value under the child tag:
//child
I'm a Java developer, so I don't know what XML libraries you'd use to do this. But you'll need a DOM parser to create a W3C Document class instance for you by reading in the XML file and then using XPath to pluck out the values.
There's a good XPath tutorial from the W3C schools if you need it.
UPDATE:
If you're saying that you already have an XML stream as String, then the answer is to not read it from a file but from the String itself. Java has abstractions called InputStream and Reader that handle streams of bytes and chars, respectively. The source can be a file, a string, etc. Check your C# DOM API to see if it has something similar. You'll pass the string to a parser that will give back a DOM object that you can manipulate.
Since the input is not well-formed XML you won't be able to parse it with any of the built in XML libraries. You'd need a regular expression to extract the well-formed piece. You could probably use one of the more forgiving HTML parsers like HtmlAgilityPack on CodePlex.
This is my solution to match any type of xml using Regex:
C# Better way to detect XML?
The XmlTextReader can parse XML fragments with a special constructor which may help in this situation, but I'm not positive about that.
There's an in-depth article here:
http://geekswithblogs.net/kobush/archive/2006/04/20/75717.aspx

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