.NET XML序列化错误:选择标识符的值无效或丢失

以下说明来自：

.NET XML序列化错误（存在反映类型的错误）

基于XmlChoiceIdentifier 创建对象

http://msdn.microsoft.com/en-us/library/system.xml.serialization.xmlchoiceidentifierattribute（v=vs.110）.aspx

我尝试使用XmlChoiceIdentifier属性序列化对象数组。但显然序列化程序需要一个数组，而ObservableCollection将导致序列化程序抛出并出错（第一个链接）。我真的需要一个ObservableCollection来保持UI的更新。因此，我试图让序列化引擎访问数组，而UI则以浪费资源的方式访问Observable集合albiet。

这是我的"解决方案"

 [XmlType(IncludeInSchema = false)]
public enum ItemChoiceType
{
    [XmlEnumAttribute("Item")]
    Item,
    [XmlEnumAttribute("Macro")]
    Macro
}
[Serializable()]
public class GroupAndItemsCollection
{
    [XmlElementAttribute(IsNullable = false)]
    [XmlIgnore]
    public ItemChoiceType[] ItemTypeArray;
    [XmlAttribute(AttributeName = "name")]
    public string Group
    {
        get { return m_Group; }
        set
        {
            if (m_Group == value)
                return;
            m_Group = value;
            //OnPropertyChanged("Group");
        }
    }
    private ObservableCollection<ListItemName> m_items;
    private ListItemName[] m_itemsArray;
    [XmlIgnore]
    public ObservableCollection<ListItemName> Items
    {
        get
        {
            if (m_items != null && ItemsArray != null && m_items.Except(ItemsArray).Any())
            {
            m_items = new ObservableCollection<ListItemName>(ItemsArray);
            }
            return m_items;
        }
        set
        {
            m_items = value;
            ItemsArray = new ListItemName[m_items.Count];
            for (int i = 0; i < m_items.Count; i++)
            {
                ItemsArray[i] = m_items[i];
            }
        }
    }
[XmlChoiceIdentifier("ItemTypeArray")]
    [XmlElement(ElementName = "Item", Type = typeof(ObservableCollection<ListItemName>))]
    [XmlElement(ElementName = "Macro", Type = typeof(ObservableCollection<ListItemName>))]
    public ListItemName[] ItemsArray
    {
        get { return m_itemsArray; }
        set { m_itemsArray = value; }
    }

    public GroupAndItemsCollection()
    {
        //to expand nodes in XamDataTree
        IsExpanded = true;
        Items = new ObservableCollection<ListItemName>();
        Items.CollectionChanged += Items_CollectionChanged;
    }
    void Items_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        ItemsArray = new ListItemName[m_items.Count];
        for (int i = 0; i < m_items.Count; i++)
        {
            ItemsArray[i] = m_items[i];
        }
    }
}

然后在我的主要方法中，我尝试通过以下操作进行序列化：

using (StreamWriter writer = new StreamWriter(dlg.FileName))
                    {
                        ItemChoiceType[] ic = new ItemChoiceType[]
                        {
                            ItemChoiceType.Item, 
                            ItemChoiceType.Macro
                        };
                        XmlSerializer xml = null;
                                group.ItemTypeArray = ic;
                            xml = new XmlSerializer(typeof(GroupAndItemsCollection));
                            xml.Serialize(writer, group);

                        writer.Close();
                    }

使用此解决方案，我得到以下错误：

System.InvalidOperationException occurred

HResult=-2146233079
  Message=There was an error generating the XML document.
  Source=System.Xml
  StackTrace:
       at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id)
       at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o, XmlSerializerNamespaces namespaces)
       at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o)
       at Otometrics.ICSSuite.Reports.ViewModel.EditReportVM.<InitializeCommands>b__38(Object o) in 
  InnerException: System.InvalidOperationException
       HResult=-2146233079
       Message=Invalid or missing value of the choice identifier 'ItemTypeArray' of type 'ItemChoiceType[]'.
       Source=Microsoft.GeneratedCode
       StackTrace:
            at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterCustomReportList.Write4_GroupAndItemsCollection(String n, String ns, GroupAndItemsCollection o, Boolean isNullable, Boolean needType)

现在，如果我选择忽略尝试同步数组和可观察的集合，序列化就可以了。。。下面的代码序列化得很好。

[XmlType(IncludeInSchema = false)]
public enum ItemChoiceType
{
    [XmlEnumAttribute("Item")]
    Item,
    [XmlEnumAttribute("Macro")]
    Macro
}
[Serializable()]
public class GroupAndItemsCollection
{
    [XmlElementAttribute(IsNullable = false)]
    [XmlIgnore]
    public ItemChoiceType[] ItemTypeArray;
    [XmlAttribute(AttributeName = "name")]
    public string Group
    {
        get { return m_Group; }
        set
        {
            if (m_Group == value)
                return;
            m_Group = value;
            //OnPropertyChanged("Group");
        }
    }
    private ListItemName[] m_itemsArray;
[XmlChoiceIdentifier("ItemTypeArray")]
    [XmlElement(ElementName = "Item", Type = typeof(ObservableCollection<ListItemName>))]
    [XmlElement(ElementName = "Macro", Type = typeof(ObservableCollection<ListItemName>))]
    public ListItemName[] ItemsArray
    {
        get { return m_itemsArray; }
        set { m_itemsArray = value; }
    }

    public GroupAndItemsCollection()
    {
        IsExpanded = true;
    }
}

那么，我前面的例子是什么让XmlSerializer像这样失败的呢：

Message=Invalid or missing value of the choice identifier 'ItemTypeArray' of type 'ItemChoiceType[]'.