以下程序在运行进名为“txtbl”的TextBlock控件无法显示

Silverlight项目：DataBindingDemo 文件：ElementNameDemo.xaml

....xmlns:local="clr-namespace:DataBindingDemo"...

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">             <TextBlock Height="30" HorizontalAlignment="Left" Margin="118,54,0,0" Name="txtblk" VerticalAlignment="Top" Width="210">                 <TextBlock.Text>                     <Binding ElementName="slider1" Path="Value">                         <Binding.Converter>                             <local:TruncationConverter/>                         </Binding.Converter>                     </Binding>                 </TextBlock.Text>             </TextBlock>             <Rectangle Height="200" HorizontalAlignment="Left" Margin="333,224,0,0" Name="rectangle1" Stroke="Yellow" StrokeThickness="1" VerticalAlignment="Top">                 <Rectangle.Width>                     <Binding ElementName="slider1" Path="Value"></Binding>                 </Rectangle.Width>                 <Rectangle.RenderTransform>                     <RotateTransform x:Name="rotate" Angle="90"/>                 </Rectangle.RenderTransform>             </Rectangle>             <Slider Height="256" HorizontalAlignment="Left" Margin="2,345,0,0" Name="slider1" VerticalAlignment="Top" Width="448"  Maximum="360"  />         </Grid>

隐藏文件：

 public ElementNameDemo()         {            

            InitializeComponent();             Binding binding = new Binding();             binding.ElementName = "rotate";             binding.Path = new PropertyPath("Angle");             binding.Mode = BindingMode.TwoWay;

BindingOperations.SetBinding(slider1, Slider.ValueProperty, binding);         }

TruncationConverter类： 

public class TruncationConverter:IValueConverter     {         public object Convert(object value, Type targetType, object parameter, CultureInfo culture)         {             if (value is double)                 //将双精度浮点舍入为最接近的整数值                 return Math.Round((double)value);             return value;         }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)         {             return value;         }