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？
