The type was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically.

Post from: http://www.johnsoer.com/blog/?p=125&cpage=1#comment-5494

1. public class Test
2. {
3. private string _Field = "";
4. public string Field
5. {
6. get { return _Field; }
7. set { _Field = value; }
8. }
9. }
11. public class TestInherited : Test
12. {
13. }
15. public class Container
16. {
17. private Test ivField;
18. public Test Field
19. {
20. get { return _Field; }
21. set { _Field = value; }
22. }
23. }
25. Container _Test = new Container();
26. _Test.Field = new TestInherited();

Solution:

new XmlSerializer(typeof(Container), new Type[] { typeof(TestInherited) });

This solution was not working for me because:

There was a namspace on my XmlRoot element [XmlRoot("Container", Namespace = "http://namespace", IsNullable = false)]

When i removed namespase, the problem was gone.

Hope this helps someone.