Wpf 从两个不同的UserControl绑定两个依赖项属性

我创建了两个单独的用户控件，它们可以一起工作

第一个是一个简单的用户控件，它附加了一个拇指，拇指通过拖动使控件移动，这很简单而且有效

XAML：

第二个用户控件称为直线，它由一个直线控件组成

XAML：

在这里，我尝试在mainwindow.xaml上将它们绑定在一起：

<Canvas>
    <local:ThumbPoint x:Name="ThumbPoint"/>
    <local:StraightLine StartPosition="{Binding Position, ElementName=ThumbPoint}"/>
</Canvas>

理想效果：应更新直线的从属属性起始位置

---

发生了什么：它没有被更新，所以只有拇指点在移动。

绑定没有为DP使用公共属性包装（

public Point StartPosition

），它直接使用

SetValue（）

，因此不会调用setter中的代码

需要的是propertyChangedCallback：

public Point StartPosition
{
    get { return (Point)GetValue(StartPositionProperty); }
    set { SetValue(StartPositionProperty, value); }
}

public static readonly DependencyProperty StartPositionProperty =
    DependencyProperty.Register("StartPosition", typeof(Point), typeof(StraightLine), new PropertyMetadata(new Point(), OnStartPositionChanged));

private static void OnStartPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) 
{
   StraightLine c = (StraightLine) d;
   c.Line.X1 = c.StartPosition.X; 
   c.Line.Y1 = c.StartPosition.Y; 
}

在ThumbPoint

public Point Position

中，属性也有相同的问题，但它在那里工作，因为您直接使用setter:

Position=new Point（）

或者以xaml形式绑定X1和Y1值：

<Canvas>
    <Line x:Name="Line" Stroke="Gray" StrokeThickness="1"
          X1="{Binding StartPosition.X, RelativeSource={RelativeSource AncestorType=StraightLine}}"
          Y1="{Binding StartPosition.Y, RelativeSource={RelativeSource AncestorType=StraightLine}}"/>
</Canvas>

（或使用ElementName而不是RelativeSource）

public partial class StraightLine : UserControl
{
    public Point StartPosition
    {
        get { return (Point)GetValue(StartPositionProperty); }
        set { SetValue(StartPositionProperty, value); Line.X1 = value.X; Line.Y1 = value.Y; }
    }

    // Using a DependencyProperty as the backing store for StartPosition.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty StartPositionProperty =
        DependencyProperty.Register("StartPosition", typeof(Point), typeof(StraightLine), new PropertyMetadata(new Point()));

    public StraightLine()
    {
        InitializeComponent();

        Line.X1 = 0;
        Line.Y1 = 0;

        Line.X2 = 300;
        Line.Y2 = 200;
    }
}

<Canvas>
    <local:ThumbPoint x:Name="ThumbPoint"/>
    <local:StraightLine StartPosition="{Binding Position, ElementName=ThumbPoint}"/>
</Canvas>

public Point StartPosition
{
    get { return (Point)GetValue(StartPositionProperty); }
    set { SetValue(StartPositionProperty, value); }
}

public static readonly DependencyProperty StartPositionProperty =
    DependencyProperty.Register("StartPosition", typeof(Point), typeof(StraightLine), new PropertyMetadata(new Point(), OnStartPositionChanged));

private static void OnStartPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) 
{
   StraightLine c = (StraightLine) d;
   c.Line.X1 = c.StartPosition.X; 
   c.Line.Y1 = c.StartPosition.Y; 
}

<Canvas>
    <Line x:Name="Line" Stroke="Gray" StrokeThickness="1"
          X1="{Binding StartPosition.X, RelativeSource={RelativeSource AncestorType=StraightLine}}"
          Y1="{Binding StartPosition.Y, RelativeSource={RelativeSource AncestorType=StraightLine}}"/>
</Canvas>