自定义复合集合不工作

我已经尝试过多次编写自定义CompositeCollection和CollectionContainer，我正要放弃。这是我有的。这看起来很简单。

MainPage.xaml

<phone:PhoneApplicationPage.Resources>
    <vm:MainViewModel x:Key="ViewModel"/>
</phone:PhoneApplicationPage.Resources>
<phone:Panorama DataContext="{StaticResource ViewModel}">        
    <phone:Panorama.ItemsSource>
        <app:CompositeCollection>
            <app:CompositeContainer Collection="{Binding People}"/>
            <models:PersonModel FirstName="John" LastName="Doe"/>
        </app:CompositeCollection>
    </phone:Panorama.ItemsSource>
    <phone:Panorama.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBlock Text="{Binding FirstName}"/>
                <TextBlock Text="{Binding LastName}"/>
            </StackPanel>
        </DataTemplate>
    </phone:Panorama.ItemTemplate>
</phone:Panorama>

CompositeCollection.cs

namespace PanoramaApp1
{
    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Collections.ObjectModel;
    public class CompositeCollection : ObservableCollection<object>
    {
        Collection<IEnumerable> _collections;
        public CompositeCollection()
            : base()
        {
            _collections = new Collection<IEnumerable>();
        }
        public CompositeCollection(IEnumerable<object> collection)
            : this()
        {
            if (null == collection)
            {
                throw new ArgumentNullException("collection");
            }
            foreach (object obj in collection)
            {
                base.Add(obj);
            }
        }
        public CompositeCollection(List<object> list)
            : this()
        {
            if (null == list)
            {
                throw new ArgumentNullException("list");
            }
            foreach (object obj in list)
            {
                base.Add(obj);
            }
        }
        protected override void ClearItems()
        {
            base.Clear();
            _collections.Clear();
        }
        protected override void InsertItem(int index, object item)
        {
            CompositeContainer container = item as CompositeContainer;
            if (null != container && null != container.Collection)
            {
                InsertContainer(index, container);
            }
            else
            {
                base.InsertItem(index, item);
            }
        }
        private void InsertContainer(int index, CompositeContainer container)
        {
            IEnumerable collection = _collections[index] = container.Collection;
            foreach (object obj in collection)
            {
                base.InsertItem(index++, obj);
            }
        }
        protected override void RemoveItem(int index)
        {
            IEnumerable collection = _collections[index];
            if (null != collection)
            {
                RemoveContainer(index, collection);
            }
            else
            {
                base.RemoveItem(index);
            }
        }
        private void RemoveContainer(int index, IEnumerable collection)
        {
            foreach (object obj in collection)
            {
                base.RemoveItem(index++);
            }
            _collections.RemoveAt(index);
        }
        protected override void SetItem(int index, object item)
        {
            RemoveItem(index);
            InsertItem(index, item);
        }
    }
}

CompositeContainer.cs

namespace PanoramaApp1
{
    using System.Collections;
    using System.Windows;
    public class CompositeContainer : DependencyObject
    {
        public IEnumerable Collection
        {
            get { return (IEnumerable)GetValue(CollectionProperty); }
            set { SetValue(CollectionProperty, value); }
        }
        public static readonly DependencyProperty CollectionProperty =
            DependencyProperty.Register(
            "Collection",
            typeof(IEnumerable),
            typeof(CompositeContainer),
            new PropertyMetadata(null));
    }
}

MainViewModel.cs

using Models;
using System.Collections.ObjectModel;
namespace ViewModels
{
    public class MainViewModel
    {
        public MainViewModel()
        {
            this.People = new ObservableCollection<object>();
            People.Add(new PersonModel("Jane", "Doe"));
            People.Add(new PersonModel("Joe", "Doe"));
            People.Add(new PersonModel("James", "Doe"));
        }
        public ObservableCollection<object> People { get; private set; }
    }
}

PersonModel.cs

using System.ComponentModel;
namespace Models
{
    public class PersonModel : INotifyPropertyChanging, INotifyPropertyChanged
    {
        public event PropertyChangingEventHandler PropertyChanging;
        public event PropertyChangedEventHandler PropertyChanged;
        private string _firstName;
        private string _lastName;
        public PersonModel(string firstName)
        {
            this.FirstName = firstName;
        }
        public PersonModel(string firstName, string lastName)
            : this(firstName)
        {
            this.LastName = lastName;
        }
        public string FirstName
        {
            get { return _firstName; }
            set
            {
                RaisePropertyChanging("FirstName");
                _firstName = value;
                RaisePropertyChanged("FirstName");
            }
        }
        public string LastName
        {
            get { return _lastName; }
            set
            {
                RaisePropertyChanging("LastName");
                _lastName = value;
                RaisePropertyChanged("LastName");
            }
        }
        private void RaisePropertyChanging(string propertyName)
        {
            if (null != PropertyChanging)
            {
                PropertyChanging(this, new PropertyChangingEventArgs(propertyName));
            }
        }
        private void RaisePropertyChanged(string propertyName)
        {
            if (null != PropertyChanged)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

如果我注释掉xaml中的PersonModel对象，应用程序会启动，但不会填充全景图。如果我不加注释，我得到一个非常无用的异常，说PersonModel对象"无法实例化"。ItemsControl的ItemsSource属性的类型是IEnumerable，似乎我枚举容器的权利。帮助吗?好吗?lol

---

编辑:谢谢，无参数构造函数修复了第一个问题。第二个问题仍然存在:它现在确实用PersonModel对象填充第二个全景项，但第一个全景项仍然是空的。似乎它将整个第一个panoramaitem绑定到IEnumerable，而不是插入单个元素。

设计器显示如下:i.imgur.com/4fAPe0N.jpg仿真器显示如下:i.imgur.com/UzdyMqk.png i.imgur.com/SWJZ28H.png

new PersonModel() { FirstName="John", LastName="Doe" };