Silverlight 3 中的依赖属性和数据上下文
我正在使用 Silverlight 3 beta,但遇到了问题。 我有一个页面,其中有一个我在上面写的用户控件。 用户控件具有依赖属性。 如果用户控件未定义数据上下文(因此使用父级的数据上下文),则一切正常。 但是,如果用户控件有自己的数据上下文,则永远不会调用依赖项属性的 OnPropertyChanged 方法。
下面是一个示例:
我的主页:
<UserControl x:Class="TestDepProp.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:app="clr-namespace:TestDepProp"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Width="400" Height="100">
<Grid x:Name="LayoutRoot" Background="White">
<Border BorderBrush="Blue" BorderThickness="3" CornerRadius="3">
<StackPanel Orientation="Horizontal">
<StackPanel Orientation="Vertical">
<TextBlock Text="Enter text here:" />
<TextBox x:Name="entryBlock" Text="{Binding Data, Mode=TwoWay}"/>
<Button Content="Go!" Click="Button_Click" />
<TextBlock Text="{Binding Data}" />
</StackPanel>
<Border BorderBrush="Blue" BorderThickness="3" CornerRadius="3" Margin="5">
<app:TestControl PropOnControl="{Binding Data}" />
</Border>
</StackPanel>
</Border>
</Grid>
</UserControl>
主页代码:
using System.Windows;
using System.Windows.Controls;
namespace TestDepProp
{
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
MainPageData data = new MainPageData();
this.DataContext = data;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
int i = 1;
i++;
}
}
}
主页的数据上下文:
using System.ComponentModel;
namespace TestDepProp
{
public class MainPageData:INotifyPropertyChanged
{
string _data;
public string Data
{
get
{
return _data;
}
set
{
_data = value;
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Data"));
}
}
public MainPageData()
{
Data = "Initial Value";
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
}
控件 XAML:
<UserControl x:Class="TestDepProp.TestControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:app="clr-namespace:TestDepProp"
>
<Grid x:Name="LayoutRoot" Background="White">
<StackPanel Orientation="Vertical" Margin="10" >
<TextBlock Text="This should change:" />
<TextBlock x:Name="ControlValue" Text="Not Set" />
</StackPanel>
</Grid>
</UserControl>
控件代码:
using System.Windows;
using System.Windows.Controls;
namespace TestDepProp
{
public partial class TestControl : UserControl
{
public TestControl()
{
InitializeComponent();
// Comment out next line for DP to work
DataContext = new MyDataContext();
}
#region PropOnControl Dependency Property
public string PropOnControl
{
get { return (string)GetValue(PropOnControlProperty); }
set { SetValue(PropOnControlProperty, value); }
}
public static readonly DependencyProperty PropOnControlProperty =
DependencyProperty.Register("PropOnControl", typeof(string), typeof(TestControl), new PropertyMetadata(OnPropOnControlPropertyChanged));
private static void OnPropOnControlPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TestControl _TestControl = d as TestControl;
if (_TestControl != null)
{
_TestControl.ControlValue.Text = e.NewValue.ToString();
}
}
#endregion PropOnControl Dependency Property
}
}
控件的数据上下文:
using System.ComponentModel;
namespace TestDepProp
{
public class MyDataContext : INotifyPropertyChanged
{
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
}
要尝试一下,请在文本框中键入一些内容,然后单击“执行”按钮。 注释掉控件代码中的数据上下文以查看它是否开始工作。
希望有人知道发生了什么。
I am working with Silverlight 3 beta, and am having an issue. I have a page that has a user control that I worte on it. The user control has a dependency property on it. If the user control does not define a data context (hence using the parent's data context), all works well. But if the user control has its own data context, the dependency property's OnPropertyChanged method never gets called.
Here is a sample:
My Main Page:
<UserControl x:Class="TestDepProp.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:app="clr-namespace:TestDepProp"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Width="400" Height="100">
<Grid x:Name="LayoutRoot" Background="White">
<Border BorderBrush="Blue" BorderThickness="3" CornerRadius="3">
<StackPanel Orientation="Horizontal">
<StackPanel Orientation="Vertical">
<TextBlock Text="Enter text here:" />
<TextBox x:Name="entryBlock" Text="{Binding Data, Mode=TwoWay}"/>
<Button Content="Go!" Click="Button_Click" />
<TextBlock Text="{Binding Data}" />
</StackPanel>
<Border BorderBrush="Blue" BorderThickness="3" CornerRadius="3" Margin="5">
<app:TestControl PropOnControl="{Binding Data}" />
</Border>
</StackPanel>
</Border>
</Grid>
</UserControl>
Main Page code:
using System.Windows;
using System.Windows.Controls;
namespace TestDepProp
{
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
MainPageData data = new MainPageData();
this.DataContext = data;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
int i = 1;
i++;
}
}
}
Main Page's data context:
using System.ComponentModel;
namespace TestDepProp
{
public class MainPageData:INotifyPropertyChanged
{
string _data;
public string Data
{
get
{
return _data;
}
set
{
_data = value;
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Data"));
}
}
public MainPageData()
{
Data = "Initial Value";
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
}
Control XAML:
<UserControl x:Class="TestDepProp.TestControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:app="clr-namespace:TestDepProp"
>
<Grid x:Name="LayoutRoot" Background="White">
<StackPanel Orientation="Vertical" Margin="10" >
<TextBlock Text="This should change:" />
<TextBlock x:Name="ControlValue" Text="Not Set" />
</StackPanel>
</Grid>
</UserControl>
Contol code:
using System.Windows;
using System.Windows.Controls;
namespace TestDepProp
{
public partial class TestControl : UserControl
{
public TestControl()
{
InitializeComponent();
// Comment out next line for DP to work
DataContext = new MyDataContext();
}
#region PropOnControl Dependency Property
public string PropOnControl
{
get { return (string)GetValue(PropOnControlProperty); }
set { SetValue(PropOnControlProperty, value); }
}
public static readonly DependencyProperty PropOnControlProperty =
DependencyProperty.Register("PropOnControl", typeof(string), typeof(TestControl), new PropertyMetadata(OnPropOnControlPropertyChanged));
private static void OnPropOnControlPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TestControl _TestControl = d as TestControl;
if (_TestControl != null)
{
_TestControl.ControlValue.Text = e.NewValue.ToString();
}
}
#endregion PropOnControl Dependency Property
}
}
Control's data context:
using System.ComponentModel;
namespace TestDepProp
{
public class MyDataContext : INotifyPropertyChanged
{
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
}
To try it out, type something in the text box, and hit the Go button. Comment out the data context in the controls code to see that it starts to work.
Hope someone has an idea as to what is going on.
如果你对这篇内容有疑问,欢迎到本站社区发帖提问 参与讨论,获取更多帮助,或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱,如果其他用户或者作者回复了您的评论,将不能在第一时间通知您!
发布评论
评论(1)
用户控件的数据上下文没有 Data 属性。
因为它没有数据属性,所以数据绑定返回 null,这已经是默认值,因此属性更改永远不会触发。
The user control's datacontext does not have a Data property.
Because it doesn't have a data property the databinding returns null which is already the default value so the property change never fires.