.NET XML Serialization without <?xml> text declaration

Question

I'm trying to generate XML like this:

<?xml version="1.0"?>
<!DOCTYPE APIRequest SYSTEM
"https://url">
<APIRequest>
  <Head>
      <Key>123</Key>
  </Head>
  <ObjectClass>
    <Field>Value</Field
  </ObjectClass>
</APIRequest>

I have a class (ObjectClass) decorated with XMLSerialization attributes like this:

[XmlRoot("ObjectClass")]
public class ObjectClass
{
    [XmlElement("Field")]
    public string Field { get; set; }
}

And my really hacky intuitive thought to just get this working is to do this when I serialize:

ObjectClass inst = new ObjectClass();
XmlSerializer serializer = new XmlSerializer(inst.GetType(), "");

StringWriter w = new StringWriter();
w.WriteLine(@"<?xml version=""1.0""?>");
w.WriteLine("<!DOCTYPE APIRequest SYSTEM");
w.WriteLine(@"""https://url"">");
w.WriteLine("<APIRequest>");
w.WriteLine("<Head>");
w.WriteLine(@"<Field>Value</Field>");
w.WriteLine(@"</Head>");

XmlSerializerNamespaces ns = new XmlSerializerNamespaces();
ns.Add("", ""); 
serializer.Serialize(w, inst, ns);

w.WriteLine("</APIRequest>");

However, this generates XML like this:

<?xml version="1.0"?>
<!DOCTYPE APIRequest SYSTEM
"https://url">
<APIRequest>
  <Head>
      <Key>123</Key>
  </Head>
  <?xml version="1.0" encoding="utf-16"?>
  <ObjectClass>
    <Field>Value</Field>
  </ObjectClass>
</APIRequest>

i.e. the serialize statement is automatically adding a <?xml text declaration.

I know I'm attacking this wrong so can someone point me in the right direction?

As a note, I don't think it will make practical sense to just make an APIRequest class with an ObjectClass in it (because there are say 20 different types of ObjectClass that each needs this boilerplate around them) but correct me if I'm wrong.

Automatically? You seem to be adding the declaration manually: w.WriteLine(@"<?xml version=""1.0""?>");. — Cerebrus
– Cerebrus, Commented Jun 1, 2009 at 5:47
@Cerebrus, he does not want the inner <?xml?> inside the <APIRequest> tag. — sisve
– sisve, Commented Jun 1, 2009 at 5:55
@John DataContractSeializer doesn't create header <?xml..., so he could serialize each object by this class — Arsen Mkrtchyan
– Arsen Mkrtchyan, Commented Jul 31, 2009 at 3:35
DataContractSerializer also doesn't emit DTD declarations. — John Saunders
– John Saunders, Commented May 28, 2010 at 2:02

p.campbell · Accepted Answer · 2013-01-14 16:49:59Z

36

try this:

internal static string ToXml(object obj)
{
  string retval = null;
  if (obj != null)
  {
    StringBuilder sb = new StringBuilder();
    using(XmlWriter writer = XmlWriter.Create(sb, new XmlWriterSettings() { OmitXmlDeclaration = true }))
    {
      new XmlSerializer(obj.GetType()).Serialize(writer, obj);
    }
    retval = sb.ToString();
  }
  return retval;
}

edited Jan 14, 2013 at 16:49

p.campbell

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answered Sep 17, 2010 at 8:21

Giuseppe Dimauro

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Comments

sisve · Accepted Answer · 2009-06-01 05:54:18Z

25

Never build xml using string concatenation. It's evil.

Output:

<?xml version="1.0" encoding="utf-16"?>
<!DOCTYPE APIRequest SYSTEM "https://url">
<APIRequest>
  <Head>
    <Key>123</Key>
  </Head>
  <ObjectClass>
    <Field>Value</Field>
  </ObjectClass>
</APIRequest>

Code:

using System;
using System.Diagnostics;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

public static class Program {
    public static void Main() {
        var obj = new ObjectClass { Field = "Value" };

        var settings = new XmlWriterSettings {
            Indent = true
        };

        var xml = new StringBuilder();
        using (var writer = XmlWriter.Create(xml, settings)) {
            Debug.Assert(writer != null);

            writer.WriteDocType("APIRequest", null, "https://url", null);
            writer.WriteStartElement("APIRequest");
            writer.WriteStartElement("Head");
            writer.WriteElementString("Key", "123");
            writer.WriteEndElement(); // </Head>

            var nsSerializer = new XmlSerializerNamespaces();
            nsSerializer.Add("", "");

            var xmlSerializer = new XmlSerializer(obj.GetType(), "");
            xmlSerializer.Serialize(writer, obj, nsSerializer);

            writer.WriteEndElement(); // </APIRequest>
        }

        Console.WriteLine(xml.ToString());
        Console.ReadLine();
    }
}

[XmlRoot("ObjectClass")]
public class ObjectClass {
    [XmlElement("Field")]
    public string Field { get; set; }
}

answered Jun 1, 2009 at 5:54

sisve

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2 Comments

Matt Mitchell Over a year ago

Thanks, I knew the string concat was bad but I thought it would at least work - I guess not! Thanks :-)

casperOne Over a year ago

I wouldn't say it's evil. It's not preferred, but if you have situations where performance is crucial and you've identified the writer as the source of that performance hit, then using string concatenation can be a tremendous win. Of course, it is situational, and I'd almost always use XmlWriter, but in some cases, it is justified.

nanobar · Accepted Answer · 2011-05-03 03:55:35Z

2

If you don't want to rely on an xml writer for performance reasons etc you can do this:

// Read into memory stream and set namespaces to empty strings
XmlSerializerNamespaces nsSerializer = new XmlSerializerNamespaces();
nsSerializer.Add(string.Empty, string.Empty);
XmlSerializer xs = new XmlSerializer(typeof(Model.AudioItem));
xs.Serialize(ms, item, nsSerializer);

// Read into UTF-8 stream and read off first line (i.e "<?xml version="1.0"?>")
StreamReader sr = new StreamReader(ms);
ms.Position = 0;
sr.ReadLine();

sr.ReadToEnd().ToString() now contains the naked serialization

edited May 3, 2011 at 3:55

answered May 3, 2011 at 3:07

nanobar

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1 Comment

sirthomas Over a year ago

feels dirty, and yet clever, for the ReadLine trick. I like it. Any concerns with indenting and such?

Doug Domeny · Accepted Answer · 2009-06-05 12:33:50Z

1

Derive your own XmlTextWriter to omit the XML declaration.

Private Class MyXmlTextWriter
Inherits XmlTextWriter
Sub New(ByVal sb As StringBuilder)
    MyBase.New(New StringWriter(sb))
End Sub
Sub New(ByVal w As TextWriter)
    MyBase.New(w)
End Sub

Public Overrides Sub WriteStartDocument()
    ' Don't emit XML declaration
End Sub
Public Overrides Sub WriteStartDocument(ByVal standalone As Boolean)
    ' Don't emit XML declaration
End Sub
End Class

Call Serialize with an instance of the derived MyXmlTextWriter.

Dim tw As New MyXmlTextWriter(sb)
Dim objXmlSerializer As New XmlSerializer(type)
objXmlSerializer.Serialize(tw, obj)

answered Jun 5, 2009 at 12:33

Doug Domeny

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1 Comment

John Saunders Over a year ago

@Doug D: I have trouble believing you consider this to be a better solution.

Tone · Accepted Answer · 2009-07-31 01:37:50Z

1

Scott Hanselman's got a good post on this. I used Kzu's example (which Scott's blog points to) a while back for the same thing and it worked great.

answered Jul 31, 2009 at 1:37

Tone

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1 Comment

John Saunders Over a year ago

@Tone: kind of a meee-tooo? It's just what Doug D said a month ago. -1.

CoderPi · Accepted Answer · 2016-01-19 11:26:53Z

-1

if (!string.IsNullOrEmpty(strXML) && strXML.Contains(@"<?xml"))
strXML = strXML.Remove(0, strXML.IndexOf(@"?>", 0) + 2);

edited Jan 19, 2016 at 11:26

CoderPi

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answered Jan 19, 2016 at 11:21

sas

1

2 Comments

sas Over a year ago

strXML = strXML.Remove(0, sXMLContent.IndexOf(@"?>", 0) + 2);

CoderPi Over a year ago

can you please explain your answer?

JMax · Accepted Answer · 2011-12-21 09:37:21Z

-2

One liner, to remove the first line from a string:

String.Join("\n", strXML.Split('\n').Skip(1).ToArray())

Not elegant, but concise.

edited Dec 21, 2011 at 9:37

JMax

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answered Jan 14, 2010 at 13:19

user250718

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