Serializing an object as UTF-8 XML in NET

Question

Proper object disposal removed for brevity but I m shocked if this is the simplest way to encode an object as UTF-8 in memory  There has to be an easier way doesn t there   var serializer   new XmlSerializer typeof SomeSerializableObject     var memoryStream   new MemoryStream    var streamWriter   new StreamWriter memoryStream  System Text Encoding UTF8    serializer Serialize streamWriter  entry    memoryStream Seek 0  SeekOrigin Begin   var streamReader   new StreamReader memoryStream  System Text Encoding UTF8   var utf8EncodedXml   streamReader ReadToEnd

User · Answer

I found this blog post which explains the problem very well, and defines a few different solutions:

(dead link removed)

I've settled for the idea that the best way to do it is to completely omit the XML declaration when in memory. It actually is UTF-16 at that point anyway, but the XML declaration doesn't seem meaningful until it has been written to a file with a particular encoding; and even then the declaration is not required. It doesn't seem to break deserialization, at least.

As @Jon Hanna mentions, this can be done with an XmlWriter created like this:

XmlWriter writer = XmlWriter.Create (output, new XmlWriterSettings() { OmitXmlDeclaration = true });

User · Answer

Your code doesn t get the UTF-8 into memory as you read it back into a string again  so its no longer in UTF-8  but back in UTF-16  though ideally its best to consider strings at a higher level than any encoding  except when forced to do so    To get the actual UTF-8 octets you could use   var serializer   new XmlSerializer typeof SomeSerializableObject     var memoryStream   new MemoryStream    var streamWriter   new StreamWriter memoryStream  System Text Encoding UTF8    serializer Serialize streamWriter  entry    byte   utf8EncodedXml   memoryStream ToArray      I ve left out the same disposal you ve left  I slightly favour the following  with normal disposal left in    var serializer   new XmlSerializer typeof SomeSerializableObject    using var memStm   new MemoryStream    using var  xw   XmlWriter Create memStm       serializer Serialize xw  entry     var utf8   memStm ToArray        Which is much the same amount of complexity  but does show that at every stage there is a reasonable choice to do something else  the most pressing of which is to serialise to somewhere other than to memory  such as to a file  TCP IP stream  database  etc  All in all  it s not really that verbose

User · Answer

Very good answer using inheritance  just remember to override the initializer  public class Utf8StringWriter   StringWriter       public Utf8StringWriter StringBuilder sb    base  sb                  public override Encoding Encoding   get   return Encoding UTF8

User · Answer

No  you can use a StringWriter to get rid of the intermediate MemoryStream  However  to force it into XML you need to use a StringWriter which overrides the Encoding property   public class Utf8StringWriter   StringWriter       public override Encoding Encoding   gt  Encoding UTF8      Or if you re not using C  6 yet   public class Utf8StringWriter   StringWriter       public override Encoding Encoding   get   return Encoding UTF8          Then   var serializer   new XmlSerializer typeof SomeSerializableObject    string utf8  using  StringWriter writer   new Utf8StringWriter          serializer Serialize writer  entry       utf8   writer ToString        Obviously you can make Utf8StringWriter into a more general class which accepts any encoding in its constructor - but in my experience UTF-8 is by far the most commonly required  custom  encoding for a StringWriter     Now as Jon Hanna says  this will still be UTF-16 internally  but presumably you re going to pass it to something else at some point  to convert it into binary data    at that point you can use the above string  convert it into UTF-8 bytes  and all will be well - because the XML declaration will specify  utf-8  as the encoding   EDIT  A short but complete example to show this working   using System  using System Text  using System IO  using System Xml Serialization   public class Test           public int X   get  set         static void Main                 Test t   new Test            var serializer   new XmlSerializer typeof Test            string utf8          using  StringWriter writer   new Utf8StringWriter                          serializer Serialize writer  t               utf8   writer ToString                      Console WriteLine utf8               public class Utf8StringWriter   StringWriter               public override Encoding Encoding   gt  Encoding UTF8            Result    lt  xml version  1 0  encoding  utf-8   gt   lt Test xmlns xsd  http   www w3 org 2001 XMLSchema         xmlns xsi  http   www w3 org 2001 XMLSchema-instance  gt     lt X gt 0 lt  X gt   lt  Test gt    Note the declared encoding of  utf-8  which is what we wanted  I believe

[c#] Serializing an object as UTF-8 XML in .NET

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