为什么我的UserControl绑定不能工作?

I thought this would be pretty simple to do but seems I must be missing something blinding obvious.

我原以为这很简单，但似乎我漏掉了一些显而易见的东西。

The problem is that I am passing values to my UserControl (BoxPanel) but the values are not displayed. The blue box is displayed without text.

问题是，我正在将值传递给我的UserControl (BoxPanel)，但是没有显示值。蓝色框显示没有文本。

MainWindow.xaml

MainWindow.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:l="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <l:BoxPanel Number="1" Text="Hi" />
    </Grid>
</Window>

BoxPanel.xaml

BoxPanel.xaml

<UserControl x:Class="WpfApplication1.BoxPanel"
         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" 
         Height="50" Width="90">
<Border Background="Blue">
    <StackPanel>
        <TextBlock FontSize="20" HorizontalAlignment="Center" 
            Text="{Binding Number}" />
        <Label FontSize="10" HorizontalAlignment="Center" Foreground="White" 
            Content="{Binding Text}" />
    </StackPanel>
</Border>

BoxPanel.xaml.xs

BoxPanel.xaml.xs

public partial class BoxPanel : UserControl
{
    public static readonly DependencyProperty NumberProperty = 
        DependencyProperty.Register("Number", typeof(decimal), typeof(BoxPanel));
    public static readonly DependencyProperty TextProperty = 
        DependencyProperty.Register("Text", typeof(string), typeof(BoxPanel));

    public BoxPanel()
    {
        InitializeComponent();
    }

    public decimal Number
    {
        get { return (decimal)GetValue(NumberProperty); }
        set { SetValue(NumberProperty, value); }
    }

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

1 个解决方案

#1

Binding paths, by default, are rooted at the DataContext. But you wish to bind to properties defined on the UserControl. So you have to redirect them somehow. I usually just do it by ElementName.

默认情况下，绑定路径是基于DataContext的。但是您希望绑定到UserControl上定义的属性。所以你必须重新定向它们。我通常只使用元素名。

<UserControl x:Class="WpfApplication1.BoxPanel"
         x:Name="BoxPanelRoot"
         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" 
         Height="50" Width="90">
<Border Background="Blue">
    <StackPanel>
        <TextBlock Text="{Binding Number, ElementName=BoxPanelRoot}" />
        <Label Content="{Binding Text, ElementName=BoxPanelRoot}" />
    </StackPanel>
</Border>

It seems a little odd at first, and somewhat annoying to redirect bindings like this, but it is preferrable than other methods which utilize the DataContext within the UserControl. If you block the DataContext by, say, setting it to the root of the UserControl, you have effectively blocked the best method of passing data into the UserControl.

乍一看似乎有点奇怪，像这样重定向绑定有点烦人，但它比使用UserControl中DataContext的其他方法更可取。如果将DataContext设置为UserControl的根，那么您已经有效地阻止了将数据传递到UserControl的最佳方法。

Rule of thumb, when binding in a UserControl, leave the DataContext alone unless you are explicitly binding against data passed to the UserControl.

经验法则是，在UserControl中绑定时，不要使用DataContext，除非您显式地绑定传递给UserControl的数据。

#1