Why isn't my public property serialized by the XmlSerializer?

Question

This is one i struggled with for ages so thought I'd document somewhere. (Apologies for asking and answering a question.)

(C# .net 2.0) I had a class that was being serialized by XmlSerializer, I added a new public property however it wasn't being included in the output XML.

It's not mentioned in the docs anywhere I could find, but public properties must have a set as well as a get to be serialized! I guess this is because it assumes that if you're going to serialize then you'll want to deserialize from the same file, so only serializes properties that have both a set and a get.

Answer 1

As in the question: public properties must have both a get and a set to be serialized by XmlSerializer

Answer 2

As mentioned, all properties must have both a getter and setter; annoyingly, this even includes lists. A typical collection property is read-only:

public List<Foo> Bar {get {...} }

However, for XmlSerializer you need to add a setter. Fortunately, DataContractSerializer rectifies this, but you don't have the same level of control over the xml layout (you can't use attributes, for example).

Other reasons it might not serialize:

• it isn't public with get and set (or is readonly for a field)
• it has a [DefaultValue] attribute, and is with that value
• it has a public bool ShouldSerializeFoo() method that returned false
• it has a public bool FooSpecified {get;set;} property that returned false
• it is marked [XmlIgnore]

Any of these will cause it not to serialize

Answer 3

Also properties that return null are not serialized!