xaml – 绑定ListPicker.SelectedIndex问题

我正在尝试在 Windows Phone 7 UserControl中对ListPicker的Selectedindex属性进行双向绑定.

当我设置DataContext时,它引发以下异常：
Selectedindex必须始终设置为有效值.

这是XAML代码

<Grid x:Name="LayoutRoot">
    <Grid.RowDeFinitions>
        <RowDeFinition Height="Auto"/>
        <RowDeFinition Height="Auto"/>
    </Grid.RowDeFinitions>

    <toolkit:ListPicker
        Grid.Row="0"
        x:Name="List1"
        SelectionChanged="Picker_SelectionChanged"
        Selectedindex="{Binding PickerSelectedindex,Mode=TwoWay}"
        ItemTemplate="{StaticResource PickerTemplate}"
        ItemsSource="{Binding MyList}"/>
</Grid>

而DataContext背后的代码

private ObservableCollection<MyClass> myList = null;
    public ObservableCollection<MyClass> MyList
    {
        get { return this.myList; }
        set
        {
            if (value != this.myList)
            {
                this.myList= value;
                NotifyPropertyChanged("MyList");

                this.PickerSelectedindex = 0;
            }
        }
    }

    private int pickerSelectedindex = 0;
    public int PickerSelectedindex
    {
        get
        {
            return this.pickerSelectedindex;
        }
        set
        {
            this.pickerSelectedindex= value;
        }
    }

在PickerSelectedindex.get中放置一个断点我可以看到它正确返回(0).
我确信问题是Selectedindex =“{Binding PickerSelectedindex,Mode = TwoWay}”因为删除这一行解决了问题,我可以看到ListPicker正确加载了来自MyList的数据.

我看不出问题出在哪里……

在ItemsSource解决问题后移动Selectedindex.

这是工作片段

<toolkit:ListPicker
    Grid.Row="0"
    x:Name="List1"
    SelectionChanged="Picker_SelectionChanged"
    ItemTemplate="{StaticResource PickerTemplate}"
    ItemsSource="{Binding MyList}"
    Selectedindex="{Binding PickerSelectedindex,Mode=TwoWay}"/>

有人对此有解释吗？