綁定索引屬性 UserControl

Question

我創建了用戶控件。

public partial class Line : UserControl, INotifyPropertyChanged 
{
    ObservableCollection < Point > points = new ObservableCollection< Point >();

    public static readonly DependencyProperty SpeciesPropertyPoints = DependencyProperty.Register("Points", typeof(ObservableCollection<Point>),
                         typeof(Line), null);

    public ObservableCollection<PointPath> Points
    {
        get { return (ObservableCollection<Point>)GetValue(SpeciesPropertyPoints); }
        set
        {
            SetValue(SpeciesPropertyPoints, (ObservableCollection<Point>)value);
            NotifyPropertyChanged("Points");
        }
    }

    private void Button_Click(object sender, RoutedEventArgs e)

    {
        var point = new Point(100, 50);
        points.Add(point);
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(string propertyName)

    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}


public class Point: INotifyPropertyChanged
{

   private double _x;
    public double X
    {
        get { return _x; }
        set { _x = value; }
    }

    private double _y;
    public double Y
    {
        get { return _y; }
        set { _y = value; }
    }

    public Point()
    {
        X = 0;
        Y = 0;
    }

    public Point(double x, double y)
    {
        X = x;
        Y = y;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

XAML：

  Button Click="Button_Click" 
  TextBox x:Name="x" Width="20" Text="{Binding Points[0].X}" 
  TextBox x:Name="y" Width="20" Text="{Binding Points[0].Y}" 

我想在 TexBox 中單擊名稱為“x”的按鈕顯示 Points[0].X（即 100）並在 TexBox 中單擊名稱為“y”的按鈕顯示 Points[0].Y（即 50）。 請幫我理解。

Answer 1

您應該更改文本綁定：

TextBox x:Name="x" Width="20" Text="{Binding Path=Points[0].X}" 
TextBox x:Name="y" Width="20" Text="{Binding Path=Points[0].Y}"

而你的DP實現是錯誤的，應該是這樣的

public static readonly DependencyProperty PointsProperty = DependencyProperty.Register(
        "Points", typeof (ObservableCollection<Point>), typeof (Line), new PropertyMetadata(default(ObservableCollection<Point>)));

    public ObservableCollection<Point> Points
    {
        get { return (ObservableCollection<Point>) GetValue(PointsProperty); }
        set { SetValue(PointsProperty, value); }
    }

您不應該在 DP setter 中編寫邏輯，因為它只是 CLR 屬性包裝器，並且不能保證在某些情況下會調用 setter！

編輯：