XML serialization options in .NET

Question

I'm building a service that returns an XML (no SOAP, no ATOM, just plain old XML). Say that I have my domain objects already filled with data and just need to transform them to the XML format. What options do I have on .NET?

Requirements:

• The transformation is not 1:1. Say that I have an Address property of type Address with nested properties like Line1, City, Postcode etc. This may need to result in an XML like <xaddr city="...">Line1, Postcode</xaddr>, i.e. quite different.
• Some XML elements/attributes are conditional, for example, if a Customer is under 18, the XML needs to contain some additional information.
• I only need to serialize the objects to XML, the other direction (XML to objects) is not important
• Some technologies, i.e. Data Contracts use .NET attributes. Other means of configuration (external XML config, buddy classes etc.) would be a plus.

Here are the options as I see them as the moment. Corrections / additions will be very welcome.

• String concatenation - forget it, it was a joke :)
• Linq 2 XML - complete control but quite a lot of hand written code, would need good suite of unit tests
• View engines in ASP.NET MVC (or even Web Forms theoretically), the logic being in controllers. It's a question how to structure it, I can have simple rules engine in my controller(s) and one view template per each possible output, or have the decision logic directly in the template. Both have upsides and downsides.
• XML Serialization - I'm not sure about the flexibility here
• Data Contracts from WCF - not sure about the flexibility either, plus would they work in a simple ASP.NET MVC app (non-WCF service)? Are they a super-set of the standard XML serialization now?
• If it exists, some XML-to-object mapper. The more I think about it the more I think I'm looking for something like this but I couldn't find anything appropriate.

Any comments / other options?

Answer 1

Xml Serialization works nicely. You use attributes to configure it.

You can conditionally include elements.

EDIT: I've updated the code to reflect your updated question.

[XmlRoot("pdata")]  // this element name used if serialized to doc root
public class PersonalData
{
     [XmlElement]  // with no name here, elt name = prop name
     public string Name;

     [XmlElement]  // with no name here, elt name = prop name
     public int Age;

     [XmlElement("xaddr")]  // override xml element name 
     public AddressData Address;

     [XmlElement] 
     public Under18Info Other {get; set;}

     // serialize the above element, only if Age < 18
     [XmlIgnore] // do not serialize the *Specified" property in any case
     private bool OtherSpecified {
        get { return Age < 18; }
     }
}

public class AddressData
{
     [XmlIgnore]   // do not serialize (see Composite prop)
     public string Line1 { get; set;}

     [XmlAttribute("city")] // serialize as an attribute on the parent 
     public string City {get; set;}

     [XmlIgnore]   // do not serialize 
     public string Postcode {get; set;}

     [XmlText]   // serialize as the Text node
     public string Composite 
     {
        get { return Line1 + ", " + Postcode; }
        set {
          var split = value.Split(',');
          Line1 = split[0];
          Postcode= split[1];
        }
     }
}

Then, to serialize an instance of that to a string, for example:

var pdata = new PersonalData
    {
        Name = "Gordon Brown",
        Age = 57,
        Address = new AddressData
        {
            Line1 = "10 Downing St.",
            Postcode = "1QR 3E4",
            City = "London"
        }
    };

var ns= new System.Xml.Serialization.XmlSerializerNamespaces();
ns.Add( "", "");
var s1 = new XmlSerializer(typeof(PersonalData));
var builder = new System.Text.StringBuilder();
var xmlws = new System.Xml.XmlWriterSettings { OmitXmlDeclaration = true, Indent= true };
using ( var writer = System.Xml.XmlWriter.Create(builder, xmlws))
{
    s1.Serialize(writer, pdata, ns);
}
string xml = builder.ToString();

Results:

<pdata>
  <Name>Gordon Brown</Name>
  <Age>57</Age>
  <xaddr city="London">10 Downing St., 1QR 3E4</xaddr>
</pdata>