Matevž Gačnik's Weblog

Recently I needed to specify exactly how I would like a specific class serialized. Suppose we have the following simple schema:

<xs:schema targetNamespace="http://my.favourite.ns/person.xsd"
   elementFormDefault="qualified"
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns="http://my.favourite.ns/person.xsd">
  <xs:complexType name="Person">
    <xs:sequence>
      <xs:element name="Name" type="xs:string" />
      <xs:element name="Surname" type="xs:string" />
      <xs:element name="Age" type="xs:int" minOccurs="0" />
    </xs:sequence>
  </xs:complexType>
</xs:schema>

Let's call this schema President.xsd.

A valid XML instance against this schema would be, for example:

<Person xmlns="http://my.favourite.ns/person.xsd">
   <Name>Barrack</Name>
   <Surname>Obama</Surname>
   <Age>47</Age>
</Person>

Since we are serializing against a specific XML schema (XSD), we have an option of schema compilation:

xsd /c President.xsd

This, obviously, yields a programmatic type system result in a form of a C# class. All well and done.

Now.

If we serialize the filled up class instance back to XML, we get a valid XML instance. It's valid against President.xsd.

There is a case where your schema changes ever so slightly - read, the namespaces change, and you don't want to recompile the entire solution to support this, but you still want to use XML serialization. Who doesn't - what do you do?

Suppose we want to get the following back, when serializing:

<PresidentPerson xmlns="http://schemas.gama-system.com/
      president.xsd">
   <Name>Barrack</Name>
   <Surname>Obama</Surname>
   <Age>47</Age>
</PresidentPerson>

There is an option to override the default serialization technique of XmlSerializer. Enter  the world of XmlAttributes and XmlAttributeOverrides:

private XmlSerializer GetOverridedSerializer()
{
   // set overrides for person element
   XmlAttributes attrsPerson = new XmlAttributes();
   XmlRootAttribute rootPerson =
      new XmlRootAttribute("PresidentPerson");
   rootPerson.Namespace = "http://schemas.gama-system.com/
      president.xsd";
   attrsPerson.XmlRoot = rootPerson;

   // create overrider
   XmlAttributeOverrides xOver = new XmlAttributeOverrides();
   xOver.Add(typeof(Person), attrsPerson);

   XmlSerializer xSer = new XmlSerializer(typeof(Person), xOver);
   return xSer;
}

Now serialize normally:

Stream ms = new MemoryStream();
XmlTextWriter tw = new XmlTextWriter(ms, null);
xSer.Serialize(tw, person);

This will work even if you only have a compiled version of your object graph, and you don't have any sources. System.Xml.Serialization.XmlAttributeOverrides class allows you to adorn any XML serializable class with your own XML syntax - element names, attribute names, namespaces and types.

Remember - you can override them all and still serialize your angle brackets.