String escape into XML

Question

Is there any C  function which could be used to escape and un-escape a string  which could be used to fill in the content of an XML element   I am using VSTS 2008   C     Net 3 0   EDIT 1  I am concatenating simple and short XML file and I do not use serialization  so I need to explicitly escape XML character by hand  for example  I need to put a lt b into  lt foo gt  lt  foo gt   so I need escape string a lt b and put it into element foo

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And if you want  like me when I found this question  to escape XML node names  like for example when reading from an XML serialization  use the easiest way   XmlConvert EncodeName string nameToEscape    It will also escape spaces and any non-valid characters for XML elements   http   msdn microsoft com en-us library system security securityelement escape 28VS 80 29 aspx

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EDIT  You say  I am concatenating simple and short XML file and I do not use serialization  so I need to explicitly escape XML character by hand    I would strongly advise you not to do it by hand  Use the XML APIs to do it all for you - read in the original files  merge the two into a single document however you need to  you probably want to use XmlDocument ImportNode   and then write it out again  You don t want to write your own XML parsers formatters  Serialization is somewhat irrelevant here   If you can give us a short but complete example of exactly what you re trying to do  we can probably help you to avoid having to worry about escaping in the first place     Original answer  It s not entirely clear what you mean  but normally XML APIs do this for you  You set the text in a node  and it will automatically escape anything it needs to  For example   LINQ to XML example   using System  using System Xml Linq   class Test       static void Main                 XElement element   new XElement  tag                                            Brackets  amp  stuff  lt  gt              Console WriteLine element             DOM example   using System  using System Xml   class Test       static void Main                 XmlDocument doc   new XmlDocument            XmlElement element   doc CreateElement  tag            element InnerText    Brackets  amp  stuff  lt  gt            Console WriteLine element OuterXml             Output from both examples    lt tag gt Brackets  amp amp  stuff  amp lt  amp gt  lt  tag gt    That s assuming you want XML escaping  of course  If you re not  please post more details

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WARNING  Necromancing   Still Darin Dimitrov s answer   System Security SecurityElement Escape string s  isn t complete   In XML 1 1  the simplest and safest way is to just encode EVERYTHING  Like  amp  09  for  t  It isn t supported at all in XML 1 0   For XML 1 0  one possible workaround is to base-64 encode the text containing the character s      string EncodedXml   SpecialXmlEscape                  Console WriteLine EncodedXml     string DecodedXml   XmlUnescape EncodedXml     Console WriteLine DecodedXml   public static string SpecialXmlEscape string input          string content   System Xml XmlConvert EncodeName   t          string content   System Security SecurityElement Escape   t          string strDelimiter   System Web HttpUtility HtmlEncode   t       XmlEscape   t      XmlDecode   amp  09           strDelimiter   XmlUnescape   amp  59           Console WriteLine strDelimiter         Console WriteLine string Format   amp   0      int              Console WriteLine System Text Encoding ASCII HeaderName         Console WriteLine System Text Encoding UTF8 HeaderName         string strXmlText            if  string IsNullOrEmpty input           return input        System Text StringBuilder sb   new StringBuilder         for  int i   0  i  lt  input Length    i                sb AppendFormat   amp   0      int input i               strXmlText   sb ToString        sb Clear        sb   null       return strXmlText       End Function SpecialXmlEscape   XML 1 0   public static string Base64Encode string plainText        var plainTextBytes   System Text Encoding UTF8 GetBytes plainText       return System Convert ToBase64String plainTextBytes      public static string Base64Decode string base64EncodedData        var base64EncodedBytes   System Convert FromBase64String base64EncodedData       return System Text Encoding UTF8 GetString base64EncodedBytes

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Using a third-party library  Newtonsoft Json  as alternative  public static string XmlEscape string unescaped        if  unescaped    null  return null      return JsonConvert SerializeObject unescaped        public static string XmlUnescape string escaped        if  escaped    null  return null      return JsonConvert DeserializeObject escaped  typeof string   ToString       Examples of escaped string  a lt b    gt   quot a amp lt b quot   lt foo gt  lt  foo gt     gt   quot foo amp gt  amp lt  foo amp gt  quot  NOTE  In newer versions  the code written above may not work with escaping  so you need to specify how the strings will be escaped  public static string XmlEscape string unescaped        if  unescaped    null  return null      return JsonConvert SerializeObject unescaped  new JsonSerializerSettings                 StringEscapeHandling   StringEscapeHandling EscapeHtml            Examples of escaped string  a lt b    gt   quot a u003cb quot   lt foo gt  lt  foo gt     gt   quot  u003cfoo u003e u003c foo u003e quot

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public static string XmlEscape string unescaped        XmlDocument doc   new XmlDocument        XmlNode node   doc CreateElement  root        node InnerText   unescaped      return node InnerXml     public static string XmlUnescape string escaped        XmlDocument doc   new XmlDocument        XmlNode node   doc CreateElement  root        node InnerXml   escaped      return node InnerText

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Thanks to  sehe for the one-line escape   var escaped   new System Xml Linq XText unescaped  ToString      I add to it the one-line un-escape   var unescapedAgain   System Xml XmlReader Create new StringReader   lt r gt     escaped     lt  r gt     ReadElementString

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Another take based on John Skeet s answer that doesn t return the tags   void Main         XmlString  Brackets  amp  stuff  lt  gt  and   quotes     Dump       public string XmlString string text        return new XElement  t   text  LastNode ToString         This returns just the value passed in  in XML encoded format   Brackets  amp amp  stuff  amp lt  amp gt  and  quotes

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SecurityElement Escape string s

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Following functions will do the work  Didn t test against XmlDocument  but I guess this is much faster   public static string XmlEncode string value        System Xml XmlWriterSettings settings   new System Xml XmlWriterSettings                ConformanceLevel   System Xml ConformanceLevel Fragment             StringBuilder builder   new StringBuilder         using  var writer   System Xml XmlWriter Create builder  settings                 writer WriteString value              return builder ToString       public static string XmlDecode string xmlEncodedValue        System Xml XmlReaderSettings settings   new System Xml XmlReaderSettings               ConformanceLevel   System Xml ConformanceLevel Fragment             using  var stringReader   new System IO StringReader xmlEncodedValue                 using  var xmlReader   System Xml XmlReader Create stringReader  settings                         xmlReader Read                return xmlReader Value

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George  it s simple  Always use the XML APIs to handle XML  They do all the escaping and unescaping for you   Never create XML by appending strings

[c#] String escape into XML

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