WCF DataContract serialization of read-only properties?

Question

Whenever I use WCF, I always try to make immutable classes that end up going over the wire (i.e. parameters set in constructor, properties are read-only). However, this gets

Answer 1

To ensure both immutability and easy implementation at the same time add a private setter for the property to serve deserialization. A lot happens under the bonnet, but it works.

Answer 2

If you use the DataContractSerializer (which is the default for WCF), you can serialize anyhting that's decorated with the [DataMember] attribute - even a read-only field:

[DataContract]
public class VirtualMachineTemplate : VirtualMachineTemplateBase, IXmlPicklable, IEnableLogger
{
    [DataMember]
    ulong _SizeInBytes;
}

But you need to use the DataContractSerializer - not the XML serializer. The XML serializer can ONLY serialize public properties (and it will, unless you put a [XmlIgnore] on them).

The DataContractSerializer is different:

• it doesn't need a parameter-less default constructor
• it will only serialize what you explicitly mark with [DataMember]
• but that can be anything - a field, a property, and of any visibility (private, protected, public)
• it's a bit faster than XmlSerializer, but you don't get a lot of control over the shape of the XML - you only get a say in what's included

See this blog post and this blog post for a few more tips and tricks.

Marc