我正在尝试创建一个带有可绑定属性的WPF用户控件（也许更好地说是"开发人员控件"）。我的代码包括以下文件：
----- MainWindow.xaml -----
<Window x:Class="Test_Binding.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:testBinding="clr-namespace:Test_Binding"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<testBinding:MyLabelledTextBox x:Name="MLTB" LabelText="My custom control: MyLabelledTextBox" Text="{Binding StringData, Mode=OneWay}" />
</StackPanel>
</Window>
----- MainWindow.xaml.cs -----
using System.Windows;
namespace Test_Binding
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
this.DataContext = new MyDataObject();
this.InitializeComponent();
}
}
}
----- MyDataObject.cs -----
using System.Runtime.CompilerServices; // CallerMemberName
using System.ComponentModel; // INotifyPropertyChanged
namespace Test_Binding
{
public class MyDataObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string stringData;
public string StringData
{
get { return this.stringData; }
set
{
if (value != this.stringData)
{
this.stringData = value;
this.OnPropertyChanged();
}
}
}
private void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public MyDataObject()
{
System.Timers.Timer t = new System.Timers.Timer();
t.Interval = 10000;
t.Elapsed += t_Elapsed;
t.Start();
}
private void t_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
this.StringData = ((this.StringData ?? string.Empty).Length >= 4 ? string.Empty : this.StringData + "*");
}
}
}
----- MyLabelledTextBox.xaml -----
<UserControl x:Class="Test_Binding.MyLabelledTextBox"
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">
<StackPanel Background="Yellow">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*" />
<ColumnDefinition Width="0.5*" />
</Grid.ColumnDefinitions>
<Label x:Name="MLTBLabel" Grid.Row="0" Grid.Column="0" />
<TextBox x:Name="MLTBTextBox" Grid.Row="0" Grid.Column="1" Background="Yellow" Text="{Binding Text, Mode=TwoWay}" />
</Grid>
</StackPanel>
</UserControl>
----- MyLabelledTextBox.xaml.cs -----
using System.Windows;
using System.Windows.Controls;
namespace Test_Binding
{
/// <summary>
/// Interaction logic for MyLabelledTextBox.xaml
/// </summary>
public partial class MyLabelledTextBox : UserControl
{
public static readonly DependencyProperty LabelTextProperty =
DependencyProperty.Register("LabelText", typeof(string), typeof(MyLabelledTextBox),
new PropertyMetadata(string.Empty, MyLabelledTextBox.LabelTextPropertyChanged));
public string LabelText
{
get { return (string)this.GetValue(MyLabelledTextBox.LabelTextProperty); }
set { this.SetValue(MyLabelledTextBox.LabelTextProperty, value); }
}
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(string), typeof(MyLabelledTextBox),
new PropertyMetadata(string.Empty, MyLabelledTextBox.TextPropertyChanged));
public string Text
{
get { return (string)this.GetValue(MyLabelledTextBox.TextProperty); }
set { this.SetValue(MyLabelledTextBox.TextProperty, value); }
}
public MyLabelledTextBox()
{
this.InitializeComponent();
this.MLTBLabel.DataContext = this;
this.MLTBTextBox.DataContext = this;
this.MLTBTextBox.TextChanged += new TextChangedEventHandler(this.MLTBTextBox_TextChanged);
}
private void MLTBTextBox_TextChanged(object sender, TextChangedEventArgs e)
{
this.Text = this.MLTBTextBox.Text; // transfer changes from TextBox to bindable property (bindable property change notification will be fired)
}
private static void LabelTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((MyLabelledTextBox)d).MLTBLabel.Content = (string)e.NewValue; // transfer changes from bindable property to Label
}
private static void TextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((MyLabelledTextBox)d).MLTBTextBox.Text = (string)e.NewValue; // transfer changes from bindable property to TextBox
}
}
}
有一个“MyDataObject”类的实例，它有一个“StringData”属性，该属性定期使用计时器进行修改。我的用户控件绑定到它的属性“StringData”。如果在“MainWindow.xaml”文件中的绑定设置为“TwoWay”，则用户控件将不断更新，但如果我使用“OneWay”绑定，则用户控件仅更新一次，然后“MyDataObject”类的实例的“PropertyChanged”事件不再触发，因为突然间它没有订阅者。
为什么“OneWay”绑定在被调用一次后就停止工作了？ 哪些代码更改可以使“TwoWay”和“OneWay”绑定都继续工作？
Binding问题时，您应查看Visual Studio的输出窗口中显示的错误，它们会告诉您问题所在。 - Sheridan