Why Data at the root level is invalid Line 1 position 1 for XML Document

Question

I am using a third-party DLL which transmits an XML document over the internet   Why would the DLL be throwing the following exception      Data at the root level is invalid  Line 1  position 1   see below for   full exception text     Here are the first few lines of the XML Document    lt  xml version  1 0  encoding  utf-8   gt   lt REQUEST gt     lt HEADER gt       lt REQUESTID gt 8a5f6d56-d56d-4b7b-b7bf-afcf89cd970d lt  REQUESTID gt       lt MESSAGETYPE gt 101 lt  MESSAGETYPE gt       lt MESSAGEVERSION gt 3 0 2 lt  MESSAGEVERSION gt    Exception   System ApplicationException was caught       Message Unexpected exception        Source FooSDK       StackTrace             at FooSDK RequestProcessor Send String SocketServerAddress  Int32 port             at Foo ExecuteRequest Int32 messageID  IPayload payload  Provider prov             at Foo SendOrder Int32 OrderNo        InnerException  System Xml XmlException            LineNumber 1            LinePosition 1            Message Data at the root level is invalid  Line 1  position 1             Source System Xml            SourceUri               StackTrace                  at System Xml XmlTextReaderImpl Throw Exception e                  at System Xml XmlTextReaderImpl Throw String res  String arg                  at System Xml XmlTextReaderImpl ParseRootLevelWhitespace                   at System Xml XmlTextReaderImpl ParseDocumentContent                   at System Xml XmlTextReaderImpl Read                   at System Xml XmlLoader Load XmlDocument doc  XmlReader reader  Boolean preserveWhitespace                  at System Xml XmlDocument Load XmlReader reader                  at System Xml XmlDocument LoadXml String xml                  at XYZ RequestProcessor GetObjectFromXML String xmlResult                  at XYZ RequestProcessor Send String SocketServerAddress  Int32 port             InnerException

User · Answer

Remove everything before  lt  xml version  1 0  encoding  utf-8   gt   Sometimes  there is some  invisible   not visible in all text editors   Some programs add this   It s called BOM  you can read more about it here  https   en wikipedia org wiki Byte order mark Representations of byte order marks by encoding

User · Answer

I eventually figured out there was a byte mark exception and removed it using this code    string  byteOrderMarkUtf8   Encoding UTF8 GetString Encoding UTF8 GetPreamble         if  xml StartsWith  byteOrderMarkUtf8                 var lastIndexOfUtf8    byteOrderMarkUtf8 Length-1          xml   xml Remove 0  lastIndexOfUtf8

User · Answer

Main culprit for this error is logic which determines encoding when converting Stream or byte   array to  NET string  Using StreamReader created with 2nd constructor parameter detectEncodingFromByteOrderMarks set to true  will determine proper encoding and create string which does not break XmlDocument LoadXml method  public string GetXmlString string url        using var stream   GetResponseStream url       using var reader   new StreamReader stream  true       return reader ReadToEnd       no exception on  LoadXml     Common mistake would be to just blindly use UTF8 encoding on the stream or byte    Code bellow would produce string that looks valid when inspected in Visual Studio debugger  or copy-pasted somewhere  but it will produce the exception when used with Load or LoadXml if file is encoded differently then UTF8 without BOM  public string GetXmlString string url        byte   bytes   GetResponseByteArray url       return System Text Encoding UTF8 GetString bytes      potentially exception on  LoadXml     So  in the case of your third party library  they probably use 2nd approach to decode XML stream to string  thus the exception

User · Answer

if you are using XDocument Load url   to fetch xml from another domain  it s possible that the host will reject the request and return and unexpected  non-xml  result  which results in the above XmlException  See my solution to this eventuality here   XDocument Load feedUrl  returns  quot Data at the root level is invalid  Line 1  position 1  quot

User · Answer

I can give you two advices    It seems you are using  LoadXml  instead of  Load  method  In some cases  it helps me  You have an encoding problem  Could you check the encoding of the XML file and write it

[.net] Why "Data at the root level is invalid. Line 1, position 1." for XML Document?

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