WPF - 如何綁定到UserControl中的UserControl屬性，以便子更新父級？

Question

我正在嘗試使用我的自定義滑塊控件LabelSlider創建一個基本的顏色更改UserControl。 我可以通過代碼獲取顏色，但是如果我移動滑塊或在TextBox中輸入文本，它不會更新顏色。

LabelSlider XAML：

<Slider x:Name="ucSlider" x:FieldModifier="private" Margin="{Binding SliderSpacing, FallbackValue=5, Converter={StaticResource DoubleToMargin}}" VerticalAlignment="Center" Grid.Column="1" Width="{Binding SliderWidth}" MaxWidth="{Binding SliderWidth}" FontFamily="Segoe UI" Value="{Binding Value, Mode=TwoWay}" SmallChange="1" Maximum="255"/>
<TextBox x:Name="ucTextBox" x:FieldModifier="private" Text="{Binding Value, TargetNullValue=0, Mode=TwoWay}" Margin="{Binding TextBoxSpacing, FallbackValue=5, Converter={StaticResource DoubleToMargin}}" Grid.Column="2" PreviewKeyDown="LabelSlider_PreviewKeyDown" PreviewTextInput="LabelSlider_PreviewTextInput" MaxLength="3" Width="30" MaxWidth="30" FontFamily="Segoe UI" TextChanged="LabelSlider_TextChanged"/>

LabelSlider代碼背后：

public int Value
{
  get { return (int)GetValue(ValueProperty); }
  set { SetValue(ValueProperty, value); }
}

public static readonly DependencyProperty ValueProperty = DependencyProperty.Register
(
  "Value",
  typeof(int),
  typeof(LabelSlider),
  new PropertyMetadata(null)
);

ColourSelection XAML：

<UserControl x:Class="Homuli.UserControls.ColourSelection"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:Homuli.UserControls"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300" x:Name="colourSelection">
<StackPanel Margin="5,0,0,0" DataContext="{Binding ElementName=colourSelection}">
    <local:LabelSlider Label="R" SliderSpacing="6" SliderWidth="100" Value="{Binding R, FallbackValue=255, TargetNullValue=0}" Foreground="White" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="0,-4"/>
    <local:LabelSlider Label="G" SliderSpacing="5" SliderWidth="100" Value="{Binding G, FallbackValue=0, TargetNullValue=0}" Foreground="White" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="0,-4"/>
    <local:LabelSlider Label="B" SliderSpacing="6" SliderWidth="100" Value="{Binding B, FallbackValue=0, TargetNullValue=0}" Foreground="White" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="0,-4"/>
        <StackPanel Orientation="Horizontal">
            <local:LabelTextBox Label="Hex" Spacing="15" TextBoxWidth="50" Text="{Binding Hex}" MaxLength="6" Foreground="White" HorizontalAlignment="Left" VerticalAlignment="Center"/>
            <Rectangle Fill="{Binding Colour}" Height="26" Width="26" Margin="26,0,0,0" Stroke="Black" />
        </StackPanel>
    </StackPanel>

ColourSelection Code背后：

public partial class ColourSelection : UserControl
{
  public ColourSelection()
  {
    InitializeComponent();
  }

  public SolidColorBrush Colour
  {
    get { return (SolidColorBrush)GetValue(ColourProperty); }
    set { SetValue(ColourProperty, value); }
  }

  public static readonly DependencyProperty ColourProperty = DependencyProperty.Register
  (
    "Colour",
    typeof(SolidColorBrush),
    typeof(ColourSelection),
    new PropertyMetadata(null)
  );

  public int R
  {
    get { return (int)GetValue(RProperty); }
    set
    {
      if (value <= 255 && value >= 0)
      {
        SetValue(RProperty, value);
        UpdateColour();
      }
    }
  }

  public static readonly DependencyProperty RProperty = DependencyProperty.Register
  (
    "R",
    typeof(int),
    typeof(ColourSelection),
    new PropertyMetadata()
  );

  public int G
  {
    get { return (int)GetValue(GProperty); }
    set
    {
      if (value <= 255 && value >= 0)
      {
        SetValue(GProperty, value);
        UpdateColour();
      }
    }
  }

  public static readonly DependencyProperty GProperty = DependencyProperty.Register
  (
    "G",
    typeof(int),
    typeof(ColourSelection),
    new PropertyMetadata(null)
  );

  public int B
  {
    get { return (int)GetValue(BProperty); }
    set
    {
      if (value <= 255 && value >= 0)
      {
        SetValue(BProperty, value);
        UpdateColour();
      }
    }
  }
  public static readonly DependencyProperty BProperty = DependencyProperty.Register
  (
    "B",
    typeof(int),
    typeof(ColourSelection),
    new PropertyMetadata(null)
  );

  void UpdateColour()
  {
    Colour = new SolidColorBrush(Color.FromRgb((byte)R, (byte)G, (byte)B));
  }
}

任何幫助將不勝感激。

Answer 1

當DP正在改變時，它通過靜態對象BProperty發生。 設置器中的代碼

if (value <= 255 && value >= 0)
{
   SetValue(RProperty, value);
   UpdateColour();
}

沒有執行。

你需要添加屬性更改回調（對於R ， G ， B屬性）：

public int B
{
    get { return (int)GetValue(BProperty); }
    set { SetValue(BProperty, value); }
}

public static readonly DependencyProperty BProperty = DependencyProperty.Register
(
  "B",
  typeof(int),
  typeof(ColourSelection),
  new PropertyMetadata(0, PropertyChangedCallback)
);

private static void PropertyChangedCallback(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
    if ((int) e.NewValue <= 255 && (int) e.NewValue >= 0)
        ((ColourSelection) obj).UpdateColour();
}

---

我也不建議在userControl中替換dataContext，就像這個DataContext="{Binding ElementName=colourSelection}" 。 而是在綁定中使用ElementName ：

<local:LabelSlider Label="R" SliderSpacing="6" SliderWidth="100" 
                   Value="{Binding R, ElementName=colourSelection, FallbackValue=255, TargetNullValue=0}"