依赖属性重入(或者:为什么这样做?
本文关键字:为什么 这样做 或者 属性 依赖 | 更新日期: 2023-09-27 18:34:01
简而言之,我可以在 WPF 控件中创建 2 个依赖项属性,并将代码放入每个属性更改通知中以更改其他属性(即PropA
更改集PropB
和PropB
更改集PropA
)。
我希望这会消失在自己的背面,但 WPF 似乎处理得很好。这实际上对我的目的非常方便,但我在任何地方都找不到这种行为记录。
这到底是怎么回事呢?WPF 依赖项属性更改通知系统是否防止重新进入?
代表代码如下:
XAML:
<Window x:Class="WPFReentrancy1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<TextBox Text="{Binding PropB, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</Window>
代码隐藏:
public partial class MainWindow : Window
{
public string PropA
{
get { return (string)GetValue(PropAProperty); }
set { SetValue(PropAProperty, value); }
}
public static readonly DependencyProperty PropAProperty =
DependencyProperty.Register("PropA", typeof (string), typeof (MainWindow),new UIPropertyMetadata("0", PropAChanged));
public string PropB
{
get { return (string)GetValue(PropBProperty); }
set { SetValue(PropBProperty, value); }
}
public static readonly DependencyProperty PropBProperty =
DependencyProperty.Register("PropB", typeof (string), typeof (MainWindow), new UIPropertyMetadata("", PropBChanged));
private static void PropBChanged(DependencyObject lDependencyObject, DependencyPropertyChangedEventArgs lDependencyPropertyChangedEventArgs)
{
((MainWindow) lDependencyObject).PropA = (string) lDependencyPropertyChangedEventArgs.NewValue;
}
private static void PropAChanged(DependencyObject lDependencyObject, DependencyPropertyChangedEventArgs lDependencyPropertyChangedEventArgs)
{
((MainWindow) lDependencyObject).PropB =
double.Parse((string) lDependencyPropertyChangedEventArgs.NewValue).ToString("0.000");
}
public MainWindow()
{
InitializeComponent();
DataContext = this;
PropA = "1.123";
}
}
这些回调仅在属性更改时触发,您的代码不会创建不同值的无限循环。
试试这个,你会得到一个SO异常:
private static readonly Random _random = new Random();
private static void PropBChanged(DependencyObject lDependencyObject, DependencyPropertyChangedEventArgs lDependencyPropertyChangedEventArgs)
{
((MainWindow)lDependencyObject).PropA = _random.Next().ToString();
}
private static void PropAChanged(DependencyObject lDependencyObject, DependencyPropertyChangedEventArgs lDependencyPropertyChangedEventArgs)
{
((MainWindow)lDependencyObject).PropB = _random.Next().ToString();
}