场景: 一个用户控件包含一个只读的文本框和一个按钮。每当按钮按下时,TextBox.Text会被修改和更新。
问题: TextControl.Text属性绑定到了UserControl.Message依赖属性,但是当UserControl.Message从UserControl内部修改时,它不会更新。然而,当实现INotifyPropertyChanged时,目标会更新。
我真的不需要在依赖属性上实现INotifyPropertyChanged吗?我错过了什么?请参见演示代码这里。
谢谢。
Message属性声明
public static readonly DependencyProperty MessageProperty =
DependencyProperty.Register("Message", typeof (string),
typeof (TextControl), new FrameworkPropertyMetadata("[WPFApp]" +
Environment.NewLine, OnMessageChanged, OnMessageCoerce));
public string Message
{
get { return (string) GetValue(MessageProperty); }
set { SetValue(MessageProperty, value); }
}
private static object OnMessageCoerce(DependencyObject obj,
object baseValue)
{
return (string) obj.GetValue(MessageProperty) + (string) baseValue;
}
private static void OnMessageChanged(DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
// do i need to do this?
((TextControl) d).NotifyPropertyChanged("Message");
}
使用XAML缩写的UserControl
<UserControl x:Class="WPFApp.TextControl"
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="64" d:DesignWidth="355"
DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Grid>
<TextBox Text="{Binding Message, Mode=OneWay}" ... />
<Button ... />
</Grid>
</UserControl>