XmlSerializer won't serialize IEnumerable

Question

I have an invocation logger that is intended to record all method calls along with the parameters associated with the method using XmlSerializer. It works well for most of the calls, but it throws an exception for all methods that has a parameter of IEnumerable type.

For example, void MethodWithPlace( Place value ) would be serialized, but void MethodWithPlace( IEnumerable<Place> value ) would not.

The exception is

System.NotSupportedException: Cannot serialize interface System.Collections.Generic.IEnumerable`1[[Place, Test, Version=0.0.0.0, Culture=neutral]].

What should I do to make it work with those methods with IEnumerable as one of its parameters?

Answer 1

The way you serialize an IEnumerable property is with a surrogate property

[XmlRoot] public class Entity {    [XmlIgnore]    public IEnumerable<Foo> Foo { get; set; }     [XmlElement, Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]    public List<Foo> FooSurrogate { get { return Foo.ToList(); } set { Foo = value; } } } 

It's ugly, but it gets the job done. The nicer solution is to write a surrogate class (i.e. EntitySurrogate).

Answer 2

Basically an XmlSerializer can't serialize an interface. The solution, then, is to give it a concrete instance to serialize. Depending on how your invocation logger works, I would consider using

var serializer = new XmlSerializer(value.GetType());