Why does C XmlDocument LoadXml string fail when an XML header is included

Question

Does anyone have any idea why the following code sample fails with an XmlException  Data at the root level is invalid  Line 1  position 1    var body     lt  xml version  1 0  encoding  utf-16   gt  lt Report gt          XmlDocument bodyDoc   new XmlDocument                bodyDoc LoadXml body

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Simple line   bodyDoc LoadXml new MemoryStream Encoding Unicode GetBytes body

User · Answer

This really saved my day    I have written a extension method based on Zach s answer  also I have extended it to use the encoding as a parameter  allowing for different encodings beside from UTF-8 to be used  and I wrapped the MemoryStream in a  using  statement   public static class XmlHelperExtentions            lt summary gt          Loads a string through  Load   instead of  LoadXml           This prevents character encoding problems           lt  summary gt           lt param name  xmlDocument  gt  lt  param gt           lt param name  xmlString  gt  lt  param gt      public static void LoadString this XmlDocument xmlDocument  string xmlString  Encoding encoding   null             if  encoding    null                encoding   Encoding UTF8                        Encode the XML string in a byte array         byte   encodedString   encoding GetBytes xmlString               Put the byte array into a stream and rewind it to the beginning         using  var ms   new MemoryStream encodedString                 ms Flush                ms Position   0                  Build the XmlDocument from the MemorySteam of UTF-8 encoded bytes             xmlDocument Load ms

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This worked for me   var xdoc   new XmlDocument   XmlResolver   null      xdoc LoadXml xmlFragment

User · Answer

I figured it out   Read the MSDN documentation and it says to use  Load instead of LoadXml when reading from strings   Found out this works 100  of time   Oddly enough using StringReader causes problems   I think the main reason is that this is a Unicode encoded string and that could cause problems because StringReader is UTF-8 only   MemoryStream stream   new MemoryStream                byte   data   body PayloadEncoding GetBytes body Payload               stream Write data  0  data Length               stream Seek 0  SeekOrigin Begin                XmlTextReader reader   new XmlTextReader stream                   MSDN reccomends we use Load instead of LoadXml when using in memory XML payloads             bodyDoc Load reader

User · Answer

Background  Although your question does have the encoding set as UTF-16  you don t have the string properly escaped so I wasn t sure if you did  in fact  accurately transpose the string into your question   I ran into the same exception       System Xml XmlException  Data at the   root level is invalid  Line 1    position 1    However  my code looked like this   string xml     lt  xml version   1 0   encoding   utf-8     gt  n lt event gt This is a Test lt  event gt    XmlDocument xmlDoc   new XmlDocument    xmlDoc LoadXml xml     The Problem  The problem is that strings are stored internally as UTF-16 in  NET however the encoding specified in the XML document header may be different  E g     lt  xml version  1 0  encoding  utf-8   gt    From the MSDN documentation for String here      Each Unicode character in a string is   defined by a Unicode scalar value    also called a Unicode code point or   the ordinal  numeric  value of the   Unicode character  Each code point is   encoded using UTF-16 encoding  and the   numeric value of each element of the   encoding is represented by a Char   object    This means that when you pass XmlDocument LoadXml   your string with an XML header  it must say the encoding is UTF-16  Otherwise  the actual underlying encoding won t match the encoding reported in the header and will result in an XmlException being thrown   The Solution  The solution for this problem is to make sure the encoding used in whatever you pass the Load or LoadXml method matches what you say it is in the XML header  In my example above   either change your XML header to state UTF-16 or to encode the input in UTF-8 and use one of the XmlDocument Load methods   Below is sample code demonstrating how to use a MemoryStream to build an XmlDocument using a string which defines a UTF-8 encode XML document  but of course  is stored a UTF-16  NET string    string xml     lt  xml version   1 0   encoding   utf-8     gt  n lt event gt This is a Test lt  event gt        Encode the XML string in a UTF-8 byte array byte   encodedString   Encoding UTF8 GetBytes xml       Put the byte array into a stream and rewind it to the beginning MemoryStream ms   new MemoryStream encodedString   ms Flush    ms Position   0      Build the XmlDocument from the MemorySteam of UTF-8 encoded bytes XmlDocument xmlDoc   new XmlDocument    xmlDoc Load ms

User · Answer

I figured it out   Read the MSDN documentation and it says to use  Load instead of LoadXml when reading from strings   Found out this works 100  of time   Oddly enough using StringReader causes problems   I think the main reason is that this is a Unicode encoded string and that could cause problems because StringReader is UTF-8 only   MemoryStream stream   new MemoryStream                byte   data   body PayloadEncoding GetBytes body Payload               stream Write data  0  data Length               stream Seek 0  SeekOrigin Begin                XmlTextReader reader   new XmlTextReader stream                   MSDN reccomends we use Load instead of LoadXml when using in memory XML payloads             bodyDoc Load reader

User · Answer

Try this   XmlDocument bodyDoc   new XmlDocument    bodyDoc XMLResolver   null  bodyDoc Load body

User · Answer

This worked for me   var xdoc   new XmlDocument   XmlResolver   null      xdoc LoadXml xmlFragment

User · Answer

I had the same issue because the XML file I was uploading was encoded using UTF-8-BOM  UTF-8 byte-order mark    Switched the encoding to UTF-8 in Notepad   and was able to load the XML file in code

User · Answer

I figured it out   Read the MSDN documentation and it says to use  Load instead of LoadXml when reading from strings   Found out this works 100  of time   Oddly enough using StringReader causes problems   I think the main reason is that this is a Unicode encoded string and that could cause problems because StringReader is UTF-8 only   MemoryStream stream   new MemoryStream                byte   data   body PayloadEncoding GetBytes body Payload               stream Write data  0  data Length               stream Seek 0  SeekOrigin Begin                XmlTextReader reader   new XmlTextReader stream                   MSDN reccomends we use Load instead of LoadXml when using in memory XML payloads             bodyDoc Load reader

User · Answer

Simple and effective solution  Instead of using the LoadXml   method use the Load   method  For example   XmlDocument xmlDoc   new XmlDocument    xmlDoc Load  sample xml

User · Answer

Try this   XmlDocument bodyDoc   new XmlDocument    bodyDoc XMLResolver   null  bodyDoc Load body

User · Answer

Background  Although your question does have the encoding set as UTF-16  you don t have the string properly escaped so I wasn t sure if you did  in fact  accurately transpose the string into your question   I ran into the same exception       System Xml XmlException  Data at the   root level is invalid  Line 1    position 1    However  my code looked like this   string xml     lt  xml version   1 0   encoding   utf-8     gt  n lt event gt This is a Test lt  event gt    XmlDocument xmlDoc   new XmlDocument    xmlDoc LoadXml xml     The Problem  The problem is that strings are stored internally as UTF-16 in  NET however the encoding specified in the XML document header may be different  E g     lt  xml version  1 0  encoding  utf-8   gt    From the MSDN documentation for String here      Each Unicode character in a string is   defined by a Unicode scalar value    also called a Unicode code point or   the ordinal  numeric  value of the   Unicode character  Each code point is   encoded using UTF-16 encoding  and the   numeric value of each element of the   encoding is represented by a Char   object    This means that when you pass XmlDocument LoadXml   your string with an XML header  it must say the encoding is UTF-16  Otherwise  the actual underlying encoding won t match the encoding reported in the header and will result in an XmlException being thrown   The Solution  The solution for this problem is to make sure the encoding used in whatever you pass the Load or LoadXml method matches what you say it is in the XML header  In my example above   either change your XML header to state UTF-16 or to encode the input in UTF-8 and use one of the XmlDocument Load methods   Below is sample code demonstrating how to use a MemoryStream to build an XmlDocument using a string which defines a UTF-8 encode XML document  but of course  is stored a UTF-16  NET string    string xml     lt  xml version   1 0   encoding   utf-8     gt  n lt event gt This is a Test lt  event gt        Encode the XML string in a UTF-8 byte array byte   encodedString   Encoding UTF8 GetBytes xml       Put the byte array into a stream and rewind it to the beginning MemoryStream ms   new MemoryStream encodedString   ms Flush    ms Position   0      Build the XmlDocument from the MemorySteam of UTF-8 encoded bytes XmlDocument xmlDoc   new XmlDocument    xmlDoc Load ms

User · Answer

Simple line   bodyDoc LoadXml new MemoryStream Encoding Unicode GetBytes body

User · Answer

Simple and effective solution  Instead of using the LoadXml   method use the Load   method  For example   XmlDocument xmlDoc   new XmlDocument    xmlDoc Load  sample xml

User · Answer

This really saved my day    I have written a extension method based on Zach s answer  also I have extended it to use the encoding as a parameter  allowing for different encodings beside from UTF-8 to be used  and I wrapped the MemoryStream in a  using  statement   public static class XmlHelperExtentions            lt summary gt          Loads a string through  Load   instead of  LoadXml           This prevents character encoding problems           lt  summary gt           lt param name  xmlDocument  gt  lt  param gt           lt param name  xmlString  gt  lt  param gt      public static void LoadString this XmlDocument xmlDocument  string xmlString  Encoding encoding   null             if  encoding    null                encoding   Encoding UTF8                        Encode the XML string in a byte array         byte   encodedString   encoding GetBytes xmlString               Put the byte array into a stream and rewind it to the beginning         using  var ms   new MemoryStream encodedString                 ms Flush                ms Position   0                  Build the XmlDocument from the MemorySteam of UTF-8 encoded bytes             xmlDocument Load ms

User · Answer

I had the same problem when switching from absolute to relative path for my xml file  The following solves both loading and using relative source path issues  Using a XmlDataProvider  which is defined in xaml  should be possible in code too          lt Window Resources gt       lt XmlDataProvider          x Name  myDP          x Key  MyData          Source            XPath   RootElement Element          IsAsynchronous  False          IsInitialLoadEnabled  True                                   debug PresentationTraceSources TraceLevel  High     gt   lt  Window Resources gt    The data provider automatically loads the document once the source is set  Here s the code            m DataProvider   this FindResource  MyData   as XmlDataProvider          FileInfo file   new FileInfo  MyXmlFile xml             m DataProvider Document   new XmlDocument            m DataProvider Source   new Uri file FullName

User · Answer

I figured it out   Read the MSDN documentation and it says to use  Load instead of LoadXml when reading from strings   Found out this works 100  of time   Oddly enough using StringReader causes problems   I think the main reason is that this is a Unicode encoded string and that could cause problems because StringReader is UTF-8 only   MemoryStream stream   new MemoryStream                byte   data   body PayloadEncoding GetBytes body Payload               stream Write data  0  data Length               stream Seek 0  SeekOrigin Begin                XmlTextReader reader   new XmlTextReader stream                   MSDN reccomends we use Load instead of LoadXml when using in memory XML payloads             bodyDoc Load reader

User · Answer

I had the same problem when switching from absolute to relative path for my xml file  The following solves both loading and using relative source path issues  Using a XmlDataProvider  which is defined in xaml  should be possible in code too          lt Window Resources gt       lt XmlDataProvider          x Name  myDP          x Key  MyData          Source            XPath   RootElement Element          IsAsynchronous  False          IsInitialLoadEnabled  True                                   debug PresentationTraceSources TraceLevel  High     gt   lt  Window Resources gt    The data provider automatically loads the document once the source is set  Here s the code            m DataProvider   this FindResource  MyData   as XmlDataProvider          FileInfo file   new FileInfo  MyXmlFile xml             m DataProvider Document   new XmlDocument            m DataProvider Source   new Uri file FullName

User · Answer

I had the same issue because the XML file I was uploading was encoded using UTF-8-BOM  UTF-8 byte-order mark    Switched the encoding to UTF-8 in Notepad   and was able to load the XML file in code

[c#] Why does C# XmlDocument.LoadXml(string) fail when an XML header is included?

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