DataContractSerializer issue with event / delegate fields

Question

In my WPF application, I use a DataContractSerializer to serialize an object. I noticed that it cannot serialize types that have an event or delegate declaration. Consider the following error code:

 [Serializable] public abstract class BaseClass { public string Name { get; set; } public event PropertyChangedEventHandler PropertyChanged; } public class DerivedClass : BaseClass { public int Age { get; set; } } class Program { static void Main(string[] args) { DerivedClass derivedClass = new DerivedClass {Name = "Test", Age = 10}; derivedClass.PropertyChanged += (sender, eventArgs) => Console.WriteLine("hello"); DataContractSerializer serializer = new DataContractSerializer(typeof(DerivedClass)); using(FileStream stream = new FileStream("c:\\test.txt", FileMode.Create, FileAccess.ReadWrite)) { serializer.WriteObject(stream, derivedClass); } } } 

This fails with message

Type 'System.DelegateSerializationHolder + DelegateEntry' with the data contract name 'DelegateSerializationHolder.DelegateEntry: http://schemas.datacontract.org/2004/07/System ' is not expected. Add any types, not statically known, to the list of known types - for example, using the KnownTypeAttribute attribute or adding them to the list of known types passed to the DataContractSerializer.

I tried adding attributes such as [DataMember(IsRequired = false)] to the event to indicate that it should not be serialized, but nothing works.

Everything worked when I removed the [Serializable] attribute from BaseClass . I wonder why this behavior? Is it safe to avoid using the [Serializable] attribute?

.NET Platform Version: 3.5 SP1

Answer 1

 [field:NonSerialized] public event PropertyChangedEventHandler PropertyChanged; 

This says the DataContractSerializer , "Do not serialize the automatically generated EventHandlerList field for this event." Thus, any instances of objects attached to your event will not be considered part of the serialized graph of the object.