Obsolete Attribute and XML Serialization

   1: public class MyClass

   2: {

   3:     private string _internalProperty;

   4:     private string _newProperty;

   5:

   6:     [Obsolete("This is no longer required, but needed for backwards compatability")]

   7:     public string Property

   8:     {

   9:         get { return _internalProperty; }

  10:         set { _internalProperty = value; }

  11:     }

  12:

  13:     public string NewProperty

  14:     {

  15:         get { return _newProperty; }

  16:         set { _newProperty = value; }

  17:     }

  18:

  19: }

 

This is an interesting little anomaly in the way XML Serialization handles the “Obsolete” attribute on class properties when serializing to and from XML. The attribute is treated as an “XmlIgnore” attribute, meaning that the property is not serialized. It is well documented that adding the aforementioned attribute to a property in .NET 3.5 will cause this behavior, however, it is not mentioned in the same MSDN page for .NET 2.0 on the same subject.

This one caught me out. Apparently the only two ways to fix it are: to take the attributes off or use the “ShouldSerializeX” method constructs as demonstrated below…

 

   1: public bool ShouldSerializeProperty()

   2: {

   3:     return true;

   4: }