值不在ObservableCollection <TabItems>的预期范围内

我有tabcontrol控件的问题 .

我正在使用绑定和转换器动态添加项目到tabcontrol .

添加第二个tabitem时会出现以下异常（请参阅下面的代码）：值不在预期范围内

它的堆栈跟踪：

MS.Internal.XcpImports.CheckHResult（UInt32 hr）•MS.Internal.XcpImports.SetValue（IManagedPeerBase obj，DependencyProperty属性，DependencyObject doh）•MS.Internal.XcpImports.SetValue（IManagedPeerBase doh，DependencyProperty属性，Object obj） - 系统.Windows.DependencyObject.SetObjectValueToCore（DependencyProperty dp，Object value） - System.Windows.DependencyObject.SetEffectiveValue（DependencyProperty属性，EffectiveValueEntry＆newEntry，Object newValue） - System.Windows.DependencyObject.UpdateEffectiveValue（DependencyProperty属性，EffectiveValueEntry oldEntry，EffectiveValueEntry＆newEntry，ValueOperation操作）вSystem.Windows.DependencyObject.SetValueInternal（DependencyProperty dp，Object value，Boolean allowReadOnlySet）вSystem.Windows.Controls.ContentControl.set_Content（Object value）в> SilverlightApplication1.Services.TabConverter.Convert（Object value，Type targetType，Object参数，CultureInfo文化）

MainPage xaml：

<UserControl x:Class="SilverlightApplication1.MainPage"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         mc:Ignorable="d"
         d:DesignHeight="1024"
         d:DesignWidth="1280"
         xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
         xmlns:local="clr-namespace:SilverlightApplication1.Services">

<UserControl.Resources>
    <local:TabConverter x:Key="tabConverter" />
</UserControl.Resources>

<Grid x:Name="LayoutRoot"
      Background="White">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="1*" />
        <ColumnDefinition Width="4*" />
    </Grid.ColumnDefinitions>
    <ListBox SelectionChanged="ListBox_SelectionChanged">
        <ListBoxItem Content="ViewA"></ListBoxItem>
        <ListBoxItem Content="ViewB"></ListBoxItem>
    </ListBox>
    <sdk:TabControl Grid.Column="1"
                    ItemsSource="{Binding Tabs, Converter={StaticResource tabConverter}}" />
</Grid>

MainPage代码隐藏：

public partial class MainPage : UserControl {
    ViewModel viewModel = new ViewModel();

    public MainPage() {
        InitializeComponent();
        this.DataContext = viewModel;
    }

    private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e) {
        try {
            viewModel.Tabs.Add(new TabItemModel() {
                Header = "New Tab",
                Content = new Grid()
            });

            // sdk:tabcontrol does not listen CollectionChanged of viewModel.Tabs.
            // thats why:
            viewModel.Tabs = viewModel.Tabs;
        } catch (Exception) { }
    }
}

数据模型：

public class TabItemModel {
    public string Header { get; set; }
    public UIElement Content { get; set; }
}

查看型号：

public class ViewModel:INotifyPropertyChanged {
    ObservableCollection<TabItemModel> tabs = new ObservableCollection<TabItemModel>();
    public ObservableCollection<TabItemModel> Tabs {
        get { return tabs; }
        set { tabs = value; OnPropertyChanged(PropertyNames.Tabs); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    void OnPropertyChanged(string property) {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(property));
    }

    class PropertyNames {
        public const string Tabs = "Tabs";
    }
}

标签转换器：

public class TabConverter : IValueConverter {

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        try {
            var object_data = value as ObservableCollection<TabItemModel>;
            var result = new List<TabItem>();
            foreach (var item in object_data) {
                result.Add(new TabItem() { 
                    Header = item.Header,
                    Content = item.Content // if comment this, everything works
                });
            }
            return result;
        } catch (Exception e) {
            MessageBox.Show(e.StackTrace, e.Message, MessageBoxButton.OK);
            return null;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        throw new NotImplementedException();
    }
}