C#

[XmlRoot()]
public class TestObj
{
    private Object[] array = new Object[2];

    public TestObj()
    {
    }

    [XmlArray()]
    public Object[] Items
    {
        get { return array; }
        set { array = value; }
    }
}

class Program
{
    static void Main(string[] args)
    {
        TestObj t = new TestObj();

        LinkedList<String> list = new LinkedList<string>();
        list.AddLast("abcdef");

        t.Items[0] = list;
        t.Items[1] = 123;

        XmlTextWriter wr = new XmlTextWriter("test.xml",Encoding.UTF8);
        XmlSerializer s = new XmlSerializer(typeof(TestObj));

        s.Serialize(wr, t); //throws the exception

        wr.Close();
    }
}