WPF 自定义用户控件 - 数据绑定不更新 DataContext 的属性

Question

我正在封装一个我编写的快速且肮脏的水印文本框，以便我可以在我的应用程序中重用它：BetterTextBox。除了使用新文本值更新底层 DataContext 之外，一切都在其中进行。我想我在这里错过了一些简单的东西......

没有用户文本的 BetterTextBox：

带有用户文本的BetterTextBox：

BetterTextBox.xaml：

<UserControl
 x:Class="Murray.Base.Controls.BetterTextBox"
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 <Grid>
  <TextBox Text="{Binding Text, RelativeSource={RelativeSource AncestorType=UserControl}, UpdateSourceTrigger=PropertyChanged}" />
  <TextBlock
   Margin="3,0,0,1"
   HorizontalAlignment="Left"
   VerticalAlignment="Center"
   Foreground="DarkGray"
   IsHitTestVisible="False"
   Text="{Binding Watermark, RelativeSource={RelativeSource AncestorType=UserControl}}">
   <TextBlock.Style>
    <Style TargetType="{x:Type TextBlock}">
     <Setter Property="Visibility" Value="Collapsed" />
     <Style.Triggers>
      <DataTrigger Binding="{Binding Text, RelativeSource={RelativeSource AncestorType=UserControl}}" Value="">
       <Setter Property="Visibility" Value="Visible" />
      </DataTrigger>
      <DataTrigger Binding="{Binding Text, RelativeSource={RelativeSource AncestorType=UserControl}}" Value="{x:Null}">
       <Setter Property="Visibility" Value="Visible" />
      </DataTrigger>
     </Style.Triggers>
    </Style>
   </TextBlock.Style>
  </TextBlock>
 </Grid>
</UserControl>

BetterTextBox.xaml.cs：

using System.Windows;
using System.Windows.Controls;

namespace Murray.Base.Controls
{
 /// <summary>
 /// Interaction logic for BetterTextBox.xaml
 /// </summary>
 public partial class BetterTextBox : UserControl
 {
  public BetterTextBox() { InitializeComponent(); }

  public string Text { get { return (string)GetValue(TextProperty); } set { SetValue(TextProperty, value); } }

  public static readonly DependencyProperty TextProperty = DependencyProperty.Register(nameof(Text), typeof(string), typeof(BetterTextBox));

  public string Watermark { get { return (string)GetValue(WatermarkProperty); } set { SetValue(WatermarkProperty, value); } }

  public static readonly DependencyProperty WatermarkProperty = DependencyProperty.Register(nameof(Watermark), typeof(string), typeof(BetterTextBox));
 }
}

在另一个用户控件中使用 BetterTextBox：

     <baseControls:BetterTextBox
      Width="300"
      Margin="5,0,0,0"
      Text="{Binding OverrideDistributionEmail}"
      Watermark="Enter any override distribution email address(s) here..." />

数据上下文对象上的目标属性：

public string OverrideDistributionEmail { get; set; } = "[email protected]";

我可以在 setter 上放置一个断点，但它永远不会被击中。

Answer 1

试试这个：

RelativeSource Mode=FindAncestor

<TextBox Text="{Binding Text, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}, UpdateSourceTrigger=PropertyChanged}" />

代替

<TextBox Text="{Binding Text, RelativeSource={RelativeSource AncestorType=UserControl}, UpdateSourceTrigger=PropertyChanged}" />