在 WPF 中绑定两个依赖属性

Question

我声明了两个依赖属性： 首先，Color类型的FilterColor 第二个 FilterBrush 类型为 Brush。 当 FilterBrush.Color 属性更改时，我需要更新 FilterColor 的值；当 FilterColor 属性更改时，我需要更新 FilterBrush.Color 的值。 我怎样才能实现它？

Answer 1

使用 TwoWay 绑定绑定两个属性，如果您在 UI 中更改一个属性，则在属性设置器中更改另一个属性，反之亦然，并使用 INotifyPropertyChanged 通知您的 UI 该属性已更改。

Answer 2

您可以在 DependencyProperty 定义中执行此操作，也可以使用 DependencyPropertyDescriptor 在之后执行此操作

例如....

DependencyProperty Definition:

public static readonly DependencyProperty FilterColorProperty =
    DependencyProperty.Register("FilterColor", typeof(Color),
    typeof(MyUserControl),
    new PropertyMetadata(Colors.White, FilterColorChanged));

public static void FilterColorChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
    if (!(obj is MyUserControl))
        return;

    MyUserControl ctrl = (MyUserControl)obj;
    var brush = ctrl.GetBrushProperty();

    if (brush.Color != (Color)e.NewValue)
        brush.Color = (Color)e.NewValue;
}

DependencyProperty Descriptor:

DependencyPropertyDescriptor dpd = DependencyPropertyDescriptor.FromProperty(
    MyUserControl.FilterColorProperty, typeof(MyUserControl));

if (dpd != null) 
    dpd.AddValueChanged(this, delegate { FilterColor_Changed(); });

...

private void FilterColor_Changed()
{
    Color filterColor = GetFilterColor(this);
    var brush = GetBrush(this);
    if (filterColor != brush.Color)
        brush.Color = filterColor;
}

我可能有一些语法错误... 我没有编译器来执行此 操作检查代码

Answer 3

您在哪里定义这些属性：在视图模型中还是在控件中？

如果它在视图模型中，您应该使用 INotifyPropertyChanged 而不是像这样的依赖属性：

Color _filterColor;

public Color FilterColor
{
    get
    {
        return _filterColor;
    }
    {
        if (_filterColor != value)
        {
            _filterColor = value;
            RaisePropertyChanged(() => FilterColor);

            _OnFilterColorChanged();
        }
}

void _OnFilterColorChanged()
{
    _filterBrush= ...
    RaisePropertyChanged(() => FilterBrush);
}

Brush _filterBrush;

public Brush FilterBrush
{
    get
    {
        return _filterBrush;
    }
    {
        if (_filterBrush != value)
        {
            _filterBrush = value;
            RaisePropertyChanged(() => FilterBrush);

            _OnFilterBrushChanged();
        }
}

void _OnFilterBrushChanged()
{
    _filterColor= ...
    RaisePropertyChanged(() =. FilterColor);
}

如果它处于控制状态，请执行以下操作：

public Color FilterColor
{
    get { return (Color)GetValue(FilterColorProperty); }
    set { SetValue(FilterColorProperty, value); }
}
public static readonly DependencyProperty FilterColorProperty =
    DependencyProperty.Register("FilterColor", typeof(Color), typeof(MainWindow), new UIPropertyMetadata(Colors.Transparent, new PropertyChangedCallback(_OnFilterColorPropertyChanged)));

static void _OnFilterColorPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var mw = d as MainWindow;

    Color oldValue = (Color)e.OldValue;
    Color newValue = (Color)e.NewValue;

    if (null != mw && oldValue != newValue)
    {
        mw._OnFilterColorChanged(oldValue, newValue);
    }
}

bool _isFilterColorUpdating = false;

void _OnFilterColorChanged(Color oldValue, Color newValue)
{
    if (_isFilterBrushUpdating )
        return;

    _isFilterColorUpdating = true;
    Brush = ...
    _isFilterColorUpdating = false;
}

public Brush FilterBrush
{
    get { return (Brush)GetValue(FilterBrushProperty); }
    set { SetValue(FilterBrushProperty, value); }
}
public static readonly DependencyProperty FilterBrushProperty =
    DependencyProperty.Register("FilterBrush", typeof(Brush), typeof(MainWindow), new UIPropertyMetadata(Brushs.Transparent, new PropertyChangedCallback(_OnFilterBrushPropertyChanged)));

static void _OnFilterBrushPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var mw = d as MainWindow;

    Brush oldValue = (Brush)e.OldValue;
    Brush newValue = (Brush)e.NewValue;

    if (null != mw && oldValue != newValue)
    {
        mw._OnFilterBrushChanged(oldValue, newValue);
    }
}

bool _isFilterBrushUpdating = false;
void _OnFilterBrushChanged(Brush oldValue, Brush newValue)
{
    if (_isFilterColorUpdating )
        return;

    _isFilterBrushUpdating = true;
    Color = ...
    _isFilterBrushUpdating = false;
}

请注意，最后一种方法只是 hack，而且非常糟糕，我更喜欢第一种方法。