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Unexpected XML Declaration. XML Declaration must be the first node in the document and no whitespace characters are allowed to appear before it linit [duplicate]

This error,
The processing instruction target matching "[xX][mM][lL]" is not allowed
occurs whenever I run an XSLT page that begins as follows:
<?xml version="1.0" encoding="windows-1256"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:include href="../header.xsl"/>
<xsl:template match="/">
<xsl:call-template name="pstyle"/>
<xsl:call-template name="Validation"/>
<xsl:variable name="strLang">
<xsl:value-of select="//lang"/>
</xsl:variable>
<!-- ////////////// Page Title ///////////// -->
<title>
<xsl:value-of select="//ListStudentFinishedExam.Title"/>
</title>
Note: I removed any leading spaces before the first line, but the error still occurs!

Xerces-based tools will emit the following error
The processing instruction target matching "[xX][mM][lL]" is not allowed.
when an XML declaration is encountered anywhere other than at the top of an XML file.
This is a valid diagnostic message; other XML parsers should issue a similar error message in this situation.
To correct the problem, check the following possibilities:
Some blank space or other visible content exists before the <?xml ?>
declaration.
Resolution: remove blank space or any other
visible content before the XML declaration.
Some invisible content exists before the <?xml ?>
declaration. Most commonly this is a Byte Order Mark
(BOM).
Resolution:
Remove the BOM using techniques such as those suggested by the W3C
page on the BOM in HTML.
A stray <?xml ?> declaration exists within the XML content.
This can happen when XML files are combined programmatically or
via cut-and-paste. There can only be one <?xml ?> declaration
in an XML file, and it can only be at the top.
Resolution: Search for
<?xml in a case-insensitive manner, and remove all but the top XML
declaration from the file.

Debug your XML file. Either there is space or added extra or fewer tags.
For better understanding build the project through the command line. Windows: gradlew build
In my case, AndroidManifest.xml has a blank space at the very first line
<Empty Row> // This Creates the issue
<?xml version="1.0" encoding="utf-8"?>

There was auto generated Copyright message in XML and a blank line before <resources> tag, once I removed it my build was successful.

just remove this line: <?xml version="1.0" encoding="utf-8"?> because this kind of error only come because of this line or you might also check the format of your line according the mentioned line in this answer.

I had a similar issue with 50,000 rdf/xml files in 5,000 directories (the Project Gutenberg catalog file). I solved it with riot (in the jena distribution)
the directory is cache/epub/NN/nn.rdf (where NN is a number)
in the directory above the directory where all the files are, i.e. in cache
riot epub/*/*.rdf --output=turtle > allTurtle.ttl
This produces possibly many warnings but the result is in a format which can be loaded into jena (using the fuseki web interface).
surprisingly simple (at least in this case).

Another reason of the above error is corrupted jar file. I got the same error but for Junit when running unit tests. Removing jar and downloading it again fixed the issue.

in my case was a wrong path in a config file: file was not found (path was wrong) and it came out with this exception:
Error configuring from input stream. Initial cause was The processing
instruction target matching "[xX][mM][lL]" is not allowed.

For PHP, put this line of code before you start printing your XML:
while(ob_get_level()) ob_end_clean();

It's worth checking your server's folders to see if there's a stray pom.xml hanging around.
I found that I had the problem everyone else described with a malformed pom.xml, but in a folder that I didn't expect to be on the server. An old build was sticking around unwelcome D:

For my case, the tab is the trouble maker. Replace the tab with blank should resolve the issue

Strip Out XML from string

I am calling some XMLRPC API and sometimes I am getting some "dirty" response. Dirty response means that along with XML is returned some other content/html like:
<div>Some Html maybe> Or some additional string is here
<?xml version="1.0" encoding="ISO-8859-1"?>
<methodResponse>
<params>
<param>
<value><int>30</int></value>
</param>
</params>
</methodResponse>
I need a way to throw out anything what is not XML and read only XML from string response so from response above I get only:
<?xml version="1.0" encoding="ISO-8859-1"?>
<methodResponse>
<params>
<param>
<value><int>30</int></value>
</param>
</params>
</methodResponse>
If nothing it would be helpful if someone provide code which cleans only HTML and left only XML at least. Prefer code in C#

Try using a variation of this or possibly use XSLT to filter the response you get back from the API with something similar to this. XSLT is actually pretty powerful stuff when filtering XML. I know Visual Studios didn't support XSLT V.2, but if you could use V.2 in another editor its quiet useful.

How to remove all namespaces from broken XML with C#?

Here is how to remove all namespace from xml. But it is not working for me. Because sometimes I am getting broken xml feed. eg:
<?xml version="1.0" encoding="UTF-8"?>
<!-- generator="wordpress.com" -->
<rss version="2.0"
xmlns:atom="http://www.w3.org/2005/Atom"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:opensearch="http://a9.com/-/spec/opensearch/1.1/">
<channel>
<title>sabri ?lker - WordPress.com Search</title>
<link>http://tr.search.wordpress.com/?q=sabri+%C3%BClker&page=2&t=comment&s=date</link>
<description>sabri ?lker - WordPress.com Search</description>
<pubDate>Fri, 04 Jan 2013 08:58:41 +0000</pubDate>
<language>tr</language>
<image><url>http://s.wordpress.com/i/buttonw-com.png</url><width>224</width><height>58</height><title>WordPress.com</title><link>http://wordpress.com/</link></image>
<generator>http://search.wordpress.com/</generator>
<atom:link rel="self" type="application/rss+xml" href="http://tr.search.wordpress.com/?q=sabri+%C3%BClker&page=2&t=comment&s=date&f=feed" />
<atom:link rel="search" type="application/opensearchdescription+xml" href="http://en.search.wordpress.com/opensearch.xml" title="WordPress.com" />
<opensearch:totalResults>10</opensearch:totalResults><opensearch:startIndex>11</opensearch:startIndex><opensearch:itemsPerPage>10</opensearch:itemsPerPage><opensearch:Query role="request" searchTerms="sabri ?lker startPage=\"2" /></channel>
</rss>
my exceptiom is "Name cannot begin with the '2' character, hexadecimal value 0x32. Line 17, position 227." to the result. So what should I do to solved this problem.

I'd say the reason is the ill-formed searchTerms attribute:
searchTerms="sabri ?lker startPage=\"2"
It's quoted the wrong way it should use " instead of \". You could simply replace all \" with "
string input = ..; // your xml
string processedInput = input.Replace("\\\"", """);
// then feed this into your xml parser.
This should solve your issue, but it's of course not a general way of sanitizing wrong xml input. You may want to have a look at http://tidyfornet.sourceforge.net/ it can sanitize HTML, XHTML and XML.

XML tag meaning

I have a part of xml file
<Text><?xml version="1.0" encoding="utf-16"?>
<ObjectFilter xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<FilterConditions>
<FilterCondition>
<PropertyFilters>
<PropertyFilter>
<PropertyName>Message</PropertyName>
<FilterValue xsi:type="xsd:string">PPM exceeds tolerance</FilterValue>
<FilterType>strExpr</FilterType>
<Operator>eq</Operator>
<CaseSensitive>true</CaseSensitive>
<Recursive>false</Recursive>
</PropertyFilter>
</PropertyFilters>
<Enabled>true</Enabled>
<ObjectTypeName>Spo.DataModel.UnixLogMessage</ObjectTypeName>
<ObjectClassGR>
<Guid>00000000-0000-0000-0000-000000000000</Guid>
</ObjectClassGR>
Here what is node Recursive meant,,it actually like this <Recursive>false</Recursive>
but how come it like &lt ;Recursive>false&lt ;/Recursive >
Can any one help me about this

How are you getting this XML file? From a webpage?
It seems that the way you are getting the text file is translating it as an HTML document and thus turning your '<' into &lt and your '>' into &gt
You need to ensure that the page is not interpreted as HTML. You could just copy-paste everything into Notepad first for a simple solution.

Data is invalid error when loading XML

I am trying to load a very basic XML document but everytime I get to the LoadXml(string url) line, the program crashes and reports an exception ("Data at the root level is invalid. Line 1, position 1" XmlException).
XmlDocument xmldoc = new XmlDocument();
xmldoc.LoadXml(#"C:\Websites\TestHarness\TestHarness\TestHarness\ExampleXml.xml");
XmlNode node = xmldoc.DocumentElement;
My XML looks like this (this is a sample xml document from W3Schools and it opens in IE fine):
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
This is pasted exactly as is with no whitespace.
I can't see anything wrong with this code, the stack trace doesn't tell me much and I suspect there is an environmental issue somewhere. Does anyone have any ideas?
EDIT: The formatting of the XML isn't right. The XML is the same as the sample document on here: http://w3schools.com/xml/default.asp

Use Load() instead of LoadXml().

Yes, you are loading the file name as xml. But also you are missing the xml encoding....
Xml format don't allow any text just like that.
That xml should written live this:
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
Here is a nice tool to encode online.
Hope this helps... :)