c# – On-The-Fly DependencyProperties

2023年2月1日 199次阅读

我有一个类,它可以即时计算它的属性,例如：

class CircleArea
{
    public double Radius { get; set; }
    public double Area
    {
        get
        {
            return Radius * Radius * Math.PI;
        }
    }
}

我通过执行以下操作使其成为DependencyObject：

class CircleArea:
    DependencyObject
{
    public static readonly DependencyProperty RadiusProperty =
        DependencyProperty.Register("Radius", typeof(double), typeof(CircleArea));
    public double Radius
    {
        get { return (double)GetValue(RadiusProperty); }
        set
        {
            SetValue(RadiusProperty, value);
            CoerceValue(AreaProperty);
        }
    }

    internal static readonly DependencyPropertyKey AreaPropertyKey =
        DependencyProperty.RegisterReadOnly("Area", typeof(double), typeof(CircleArea), new PropertyMetadata(double.NaN));
    public static readonly DependencyProperty AreaProperty = AreaPropertyKey.DependencyProperty;
    public double Area
    {
        get
        {
            return Radius * Radius * Math.PI;
        }
    }
}

然后我在XAML中有2个文本框,一个用TwoWay绑定到Radius,另一个用OneWay绑定到Area.

如何对Radius的文本框进行编辑更新区域的文本框？

最佳答案 有几种方法可以做到这一点.

>为简单起见,您可以实现INotifyPropertyChanged,为Area使用常规属性,然后在RadiusProperty的OnDependencyPropertyChanged中触发事件.
>为了更复杂,只要Radius发生变化,就可以私下使用密钥设置AreaProperty.你的财产看起来像这样.

public static readonly DependencyProperty RadiusProperty = 
    DependencyProperty.Register(
        "Radius",  
        typeof(double), 
        typeof(CircleArea), 
        new FrameworkPropertyMetadata(0.0, OnRadiusChanged))


private static void OnRadiusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
     Area = Radius * Radius * Math.PI;
}



private static readonly DependencyPropertyKey AreaKey=
    DependencyProperty.RegisterReadOnly("Area", typeof(double)...
public static readonly DependencyProperty AreaProperty = AreaKey.DependencyProperty;

public Double Area
{
    get
    {
        return (Double)GetValue(AreaProperty);
    }
    private set
    {
        SetValue(AreaKey, value);
    }
}

您仍然可以设置单向绑定到区域.

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