PropertyChangedEventHandler是空

Question

我有以下的類，這將是綁定源：

public class Timeline : Canvas, INotifyPropertyChanged 
{ 

    public static readonly DependencyProperty TimeTextBindingPropProperty; 
    public event PropertyChangedEventHandler PropertyChanged; 

    private void OnPropertyChanged(string name) 
    { 
    if (PropertyChanged != null) 
     PropertyChanged(this, new PropertyChangedEventArgs(name)); 
    } 

    public double TimeTextBindingProp 
    { 
    get { return (double)GetValue(TimeTextBindingPropProperty); } 
    set 
    { 
     SetValue(TimeTextBindingPropProperty, value); 
     OnPropertyChanged("TimeTextBindingProp"); 
    } 
    } 

    static Timeline() 
    { 
    TimeTextBindingPropProperty = DependencyProperty.Register("TimeTextBindingProp", typeof(double), typeof(Timeline)); 
    } 
} 

然後我設置一個文本框的Text財產和timeline's TimeTextBindingProp財產之間的結合在我的主窗口：

private void InitTextBinding() 
{ 
    timeTextBinding = new Binding(); 
    timeTextBinding.Mode = BindingMode.OneWay; 
    timeTextBinding.Source = timeline; 
    timeTextBinding.Path = new PropertyPath("TimeTextBindingProp"); 
    timeTextBinding.Converter = new TimeTextConverter(); 

    BindingOperations.SetBinding(this.timeTextBox, TextBox.TextProperty, timeTextBinding); 
} 

PropertyChangedtimeline的處理程序仍然爲空，即使已設置綁定並且已呈現timeline。我究竟做錯了什麼？

編輯：

我宣佈和文字框時間軸XAML如下：

<StackPanel Orientation="Horizontal" Margin="0,10,0,5" HorizontalAlignment="Center" VerticalAlignment="Center"> 
    <TextBox Name="timeTextBox" Margin="0,0,20,0" VerticalAlignment="Center" HorizontalContentAlignment="Center" Height="20" 
          FontFamily="Tahoma" FontSize="14" BorderBrush="White" Background="White"/> 

    <Button Name="playButton" Style="{StaticResource buttonStyle}" Click="PlayButton_Click" Margin="0,0,5,0" HorizontalAlignment="Center" 
         VerticalAlignment="Center"> 
        Play 
    </Button> 

    <Button Name="stopButton" Style="{StaticResource buttonStyle}" Click="StopButton_Click" Margin="0,0,20,0" HorizontalAlignment="Center" 
         VerticalAlignment="Center"> 
        Stop 
    </Button> 

    <Slider Name="controlSlider" Height="Auto" Width="200" HorizontalAlignment="Center" VerticalAlignment="Center" IsEnabled="False"> 
     <Slider.ToolTip> 
     <TextBlock Style="{StaticResource textStyleTextBlock}">Time Slider</TextBlock> 
     </Slider.ToolTip> 
    </Slider> 
</StackPanel> 

<ScrollViewer Name="scrollViewer" Margin="0,0,10,20" Height="500" HorizontalAlignment="Stretch" VerticalAlignment="Center" Focusable="False" 
         HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto"> 
    <StackPanel> 
    <UI:FittingCanvas x:Name="containerCanvas"> 
     <timelinePanel:Timeline x:Name="timeline" TimeCursorEnabled="True" TimeMode="Minutes" Canvas.Left="0" Canvas.Top="0" Canvas.ZIndex="0" Visibility="Hidden" 
               CursorAnimBoundaryChanged="Timeline_CursorAnimBoundaryChanged" AnimationCompleted="Timeline_AnimationCompleted"/> 
    </UI:FittingCanvas> 

    <Canvas x:Name="waveFormCanvas" Height="80" Margin="0,10,0,0"/> 
    </StackPanel> 
</ScrollViewer> 

Answer 1

除了設置timeTextBinding之外，您的代碼是否更新timeTextBox.Text？也許你直接在代碼隱藏的時候將timeTextBox.Text設置爲某個值，或者你有其他一些綁定連接到它？

因爲timeTextBinding僅單向，這種改變不能被寫回到TimeTextBindingProp，並結合將簡單地被覆蓋並刪除（無任何警告），並timeline.PropertyChanged將被重置爲null。

Answer 2

你TimeTextBindingProp是一個依賴屬性，有一個NotificationChange機制，構築成的基類。你自己的OnPropertyChanged是多餘的，顯然它不被使用。

綁定仍然應該工作，雖然。