我有一个用户控件“CtrlComments”,该控件具有以下 XAML(非常基本)。
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:wpftoolkit="http://schemas.microsoft.com/wpf/2008/toolkit"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
x:Name="ucRoot">
<Grid>
<StackPanel Orientation="Horizontal">
<TextBlock Text="ID: " />
<TextBlock Text="{Binding Path=Deployment.Id}" />
</StackPanel>
</Grid>
背后的代码如下,这是使控件发挥作用的基础知识。关键是 DependencyObject typeof(DeploymentDto),它有一个 int
属性名为 Id
我们有兴趣根据上面的 XAML 绑定(bind)在窗口上显示。
public partial class CtrlComments : UserControl, INotifyPropertyChanged
{
public static readonly DependencyProperty DeploymentProperty =
DependencyProperty.Register("Deployment", typeof(DeploymentDto),
typeof(CtrlComments), new PropertyMetadata(new DeploymentDto()));
public DeploymentDto Deployment
{
get
{
return (DeploymentDto)GetValue(DeploymentProperty);
}
set
{
SetValue(DeploymentProperty, value);
OnPropertyChanged(new PropertyChangedEventArgs("Deployment"));
}
}
public CtrlComments()
{
InitializeComponent();
this.DataContext = this;
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (PropertyChanged != null)
PropertyChanged(this, e);
}
}
我们的问题是,尽管父控件和我的用户控件之间通过依赖属性的绑定(bind)正在工作(已验证)并且 OnPropertyChanged
方法触发,TextBlock
我的 XAML 中的内容没有更新。
我注意到当 OnPropertyChanged
方法运行后,事件处理程序为null
这意味着没有人会收到有关属性发生更改的通知。
我不明白为什么会这样。如果您能帮助解释我们哪里出了问题,我们将不胜感激。
谢谢!
最佳答案
我尝试复制您的问题,在这样做时,我发现我的问题出在 CtrlComments
中的以下行:
this.DataContext = this;
放弃这条线让它对我有用。另请注意(正如 @Aron 在评论中所写),在 DependencyProperty
的 setter 中不应调用 INotifyPropertyChanged
的 OnPropertyChanged
。至少对我来说根本没有必要实现 INPC。
在使用 UserControl 的 XAML 文件中,您很可能会设置另一个 DataContext
(在更高级别上,可能在 Window
中),并且因此,我想如果已经在那里设置(或覆盖),它就不会继承到用户控件。下面是我的工作代码,但也许我完全误解了你在做什么。如果是这种情况,请扩展您的问题以包括您如何使用 UserControl,因为如果这不起作用,这是回答问题的关键:)
CtrlComments.xaml:
<UserControl x:Class="WpfApplication1.CtrlComments"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<Grid>
<StackPanel Orientation="Horizontal">
<TextBlock Text="ID: "/>
<TextBlock Text="{Binding Path=Deployment.Id}"/>
</StackPanel>
</Grid>
</UserControl>
CtrlComments.xaml.cs:
namespace WpfApplication1
{
public partial class CtrlComments : UserControl
{
public static readonly DependencyProperty DeploymentProperty =
DependencyProperty.Register("Deployment", typeof(DeploymentDto), typeof(CtrlComments), new PropertyMetadata(new DeploymentDto { Id = 5 }));
public DeploymentDto Deployment
{
get { return (DeploymentDto)GetValue(DeploymentProperty); }
set
{
SetValue(DeploymentProperty, value);
}
}
public CtrlComments()
{
InitializeComponent();
}
}
}
MainWindow.xaml:
<Window x:Class="WpfApplication1.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"
xmlns:local="clr-namespace:WpfApplication1"
DataContext="{Binding RelativeSource={RelativeSource Self}}">
<StackPanel>
<local:CtrlComments x:Name="testUC" Height="100" Deployment="{Binding Deployment}"/>
<Button Click="Button_Click" Height="50" Width="100"/>
</StackPanel>
</Window>
MainWindow.xaml.cs:
namespace WpfApplication1
{
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
}
private DeploymentDto deployment = new DeploymentDto { Id = 2 };
public DeploymentDto Deployment
{
get { return deployment; }
set { deployment = value; OnPropertyChanged("Deployment"); }
}
private void Button_Click(object sender, RoutedEventArgs e)
{
Deployment = new DeploymentDto { Id = new Random().Next(100) };
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}
}
}
部署Dto:
public class DeploymentDto
{
public int Id { get; set; }
}
将 MainWindow.DataContext
绑定(bind)到它的代码隐藏是相当难看的,但由于它只是用于示例目的,我希望它没问题:)
关于c# - 无法获取内部 XAML 绑定(bind)以针对依赖项属性工作,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28871217/