Serializing object with no namespaces using DataContractSerializer

Question

How do I remove XML namespaces from an object's XML representation serialized using DataContractSerializer?

That object needs to be serialized to a very simple output XML.

• Latest & greatest - using .Net 4 beta 2
• The object will never need to be deserialized.
• XML should not have any xmlns:... namespace refs
• Any subtypes of Exception and ISubObject need to be supported.
• It will be very difficult to change the original object.

Object:

 [Serializable] 
 class MyObj
 {
     string str;
     Exception ex;
     ISubObject subobj;
 } 

Need to serialize into:

<xml>
  <str>...</str>
  <ex i:nil="true" />
  <subobj i:type="Abc">
     <AbcProp1>...</AbcProp1>
     <AbcProp2>...</AbcProp2>
  </subobj>
</xml>

I used this code:

private static string ObjectToXmlString(object obj)
{
    if (obj == null) throw new ArgumentNullException("obj");

    var serializer =
        new DataContractSerializer(
            obj.GetType(), null, Int32.MaxValue, false, false, null,
            new AllowAllContractResolver());

    var sb = new StringBuilder();
    using (var xw = XmlWriter.Create(sb, new XmlWriterSettings
    {
        OmitXmlDeclaration = true,
        NamespaceHandling = NamespaceHandling.OmitDuplicates,
        Indent = true
    }))
    {
        serializer.WriteObject(xw, obj);
        xw.Flush();

        return sb.ToString();
    }
}

From this article I adopted a DataContractResolver so that no subtypes have to be declared:

public class AllowAllContractResolver : DataContractResolver
{
    public override bool TryResolveType(Type dataContractType, Type declaredType, DataContractResolver knownTypeResolver, out XmlDictionaryString typeName, out XmlDictionaryString typeNamespace)
    {
        if (!knownTypeResolver.TryResolveType(dataContractType, declaredType, null, out typeName, out typeNamespace))
        {
            var dictionary = new XmlDictionary();
            typeName = dictionary.Add(dataContractType.FullName);
            typeNamespace = dictionary.Add(dataContractType.Assembly.FullName);
        }
        return true;
    }

    public override Type ResolveName(string typeName, string typeNamespace, Type declaredType, DataContractResolver knownTypeResolver)
    {
        return knownTypeResolver.ResolveName(typeName, typeNamespace, declaredType, null) ?? Type.GetType(typeName + ", " + typeNamespace);
    }
}

Answer 1

You need to mark the classes you want to serialize with:

[DataContract(Namespace="")]

In that case, the data contract serializer will not use any namespace for your serialized objects.

Marc

Answer 2

If you have your heart set on bypassing the default behavior (as I currently do), you create a custom XmlWriter that bypasses writing the namespace.

using System.IO;
using System.Xml;

public class MyXmlTextWriter : XmlTextWriter
{
  public MyXmlTextWriter(Stream stream)
    : base(stream, null)
  {
  }

  public override void WriteStartElement(string prefix, string localName, string ns)
  {
    base.WriteStartElement(null, localName, "");
  }
}

Then in your writer consumer, something like the following:

var xmlDoc = new XmlDocument();
DataContractSerializer serializer = new DataContractSerializer(obj.GetType());
using (var ms = new MemoryStream())
{
  using (var writer = new MyXmlTextWriter(ms))
  {
    serializer.WriteObject(writer, obj);
    writer.Flush();
    ms.Seek(0L, SeekOrigin.Begin);
    xmlDoc.Load(ms);
  }
}

And the output will have namespace declarations in it, but there will be no usages as such:

<TestObject xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <Items xmlns:d2p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
    <string>Item1</string>
    <string>Item2</string>
  </Items>
</TestObject>