Question

I’ve got a simple class that inherits from Collection and adds a couple of properties. I need to serialize this class to XML, but the XMLSerializer ignores my additional properties.

I assume this is because of the special treatment that XMLSerializer gives ICollection and IEnumerable objects. What’s the best way around this?

Here’s some sample code:

using System.Collections.ObjectModel; using System.IO; using System.Xml.Serialization;  namespace SerialiseCollection {     class Program     {         static void Main(string[] args)         {             var c = new MyCollection();             c.Add('Hello');             c.Add('Goodbye');              var serializer = new XmlSerializer(typeof(MyCollection));             using (var writer = new StreamWriter('test.xml'))                 serializer.Serialize(writer, c);         }     }      [XmlRoot('MyCollection')]     public class MyCollection : Collection<string>     {         [XmlAttribute()]         public string MyAttribute { get; set; }          public MyCollection()         {             this.MyAttribute = 'SerializeThis';         }     } } 

This outputs the following XML (note MyAttribute is missing in the MyCollection element):

<?xml version='1.0' encoding='utf-8'?> <MyCollection xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema'>     <string>Hello</string>     <string>Goodbye</string> </MyCollection> 

What I want is

<MyCollection MyAttribute='SerializeThis'      xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'      xmlns:xsd='http://www.w3.org/2001/XMLSchema'>     <string>Hello</string>     <string>Goodbye</string> </MyCollection> 

Any ideas? The simpler the better. Thanks.

Answer 1

Collections generally don’t make good places for extra properties. Both during serialization and in data-binding, they will be ignored if the item looks like a collection (IList, IEnumerable, etc – depending on the scenario).

If it was me, I would encapsulate the collection – i.e.

[Serializable] public class MyCollectionWrapper {     [XmlAttribute]     public string SomeProp {get;set;} // custom props etc     [XmlAttribute]     public int SomeOtherProp {get;set;} // custom props etc     public Collection<string> Items {get;set;} // the items } 

The other option is to implement IXmlSerializable (quite a lot of work), but that still won’t work for data-binding etc. Basically, this isn’t the expected usage.