How can you control .NET DataContract serialization so it uses XML attributes instead of elements?

Question

If I have a class marked as a DataContract and a few properties on it marked with DataMember attributes I can serialize it out to XML easily, but it would create output like:

<Person>
    <Name>John Smith</Name>
    <Email>[email protected]</Email>
    <Phone>123-123-1234</Phone>
</Person>

What I would prefer is attributes, like...

<Person Name="John Smith" Email="[email protected]" Phone="123-123-1234" />

The DataMember attribute allows me to control the Name and Order but not whether it is serialized as an element or attribute. I have looked around and found DataContractFormat and IXmlSerializable but I am hoping there is there an easier solution.

What is the easiest way to do this?

Answer 1

You can do this with the DataContractSerializer - the answer is to take over the Xml serialization yourself by implementing the IXmlSerializable interface. For write-only support - you can leave the implementation of ReadXml empty, and return null for GetSchema, and then write the implementation of WriteXml as follows:

public class MyPerson : IXmlSerializable
{
  public string Name { get; set;}
  public string Email { get; set;}
  public string Phone { get; set;}

  public XmlSchema GetSchema() { return null; }
  public void ReadXml(XmlReader reader) { }
  public void WriteXml(XmlWriter writer)
  { 
    writer.WriteAttributeString("name", Name);
    writer.WriteAttributeString("email", Email);
    writer.WriteAttributeString("phone", Phone);
  } 
}

If you're using the same type for, say, JSON serialization as well, then you are still free to add the DataContract and DataMember attributes - the DataContractSerializer will utilise the IXmlSerializable interface implementation only when writing Xml.

I blogged about this here.