c# - 不显示代码中依赖属性的更改

Question

我创建了一个按钮，它应该支持自动换行。我的按钮 XAML 代码如下所示:

<Button x:Class="POS.TouchScreen.UI.Elements.TouchButtonWPF"
             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" Height="23" HorizontalAlignment="Left" Name="buttonGrid" VerticalAlignment="Top" Width="75" BorderBrush="#FF8A97A9" Margin="4"
             DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <TextBlock Name="ButtonTextBlock" 
               HorizontalAlignment="Stretch" 
               VerticalAlignment="Stretch"
               Text="{Binding ButtonText, Mode=TwoWay}"
               TextWrapping="Wrap">
    </TextBlock> 
</Button>

我已经实现了如下所示的属性:

public static readonly DependencyProperty ButtonTextProperty = 
    DependencyProperty.Register("ButtonText", typeof(string), typeof(TouchButtonWPF), new UIPropertyMetadata("Button",new PropertyChangedCallback(OnButtonTextChanged), new CoerceValueCallback(OnCoerceButtonText)));

private static object OnCoerceButtonText(DependencyObject o, object value)
{
    TouchButtonWPF button = o as TouchButtonWPF;
    if (button != null)
        return button.OnCoerceButtonText((string)value);
    else 
        return value;
}

protected virtual string OnCoerceButtonText(string value)
{
    return value;
}

private static void OnButtonTextChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
    TouchButtonWPF button = o as TouchButtonWPF;
    if (button != null)
        button.OnButtonTextChanged((string)e.NewValue, (string) e.OldValue);
}

protected virtual void OnButtonTextChanged(string NewValue, string OldValue)
{
    this.ButtonTextBlock.Text = NewValue;
}        

public string ButtonText
{
    get { return (string)GetValue(ButtonTextProperty); }
    set { SetValue(ButtonTextProperty, value); }
}

插入 TouchButtonWPF 的实例如下所示

<tse:TouchButtonWPF ButtonText="OK" FontSize="16" Height="77" HorizontalAlignment="Left"x:Name="buttonOk" Width="85" />                

这非常有效，按钮文本显示正确。但是，当我从 C# 代码分配 ButtonText 时，文本不会更新。我正在分配变量，如下所示。

 touchButton.ButtonText = navButton.Caption;

谁能告诉我我做错了什么？请注意，事件处理程序在最初无法正常工作时已经实现，无法确定我尝试实现的功能是否需要这些事件处理程序？

期待阅读您的回复:)

Answer 1

您的问题是您直接设置了依赖属性 (this.ButtonTextBlock.Text = NewValue)。

在您执行此操作之前，this.ButtonTextBlock.Text 的值被设置为 Binding。用本地值替换绑定(bind)会删除绑定(bind)，文本将不再响应原始绑定(bind)表达式。

替换 - this.ButtonTextBlock.Text = Value;

与 - this.ButtonTextBlock.SetCurrentValue(TextProperty, value);

这将在不破坏绑定(bind)的情况下设置值