附加属性绑定在我的用户控件中失败

Question

我有一个UsersControl.xaml

<UserControl x:Name="userControl" x:Class="Lloyd.Shared.Controls.UsersControl"
         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" 
         xmlns:Interactivity="http://schemas.microsoft.com/expression/2010/interactivity"
         xmlns:Behaviors="clr-namespace:Lloyd.Shared.Controls.Behaviors"
         xmlns:local="clr-namespace:Lloyd.Shared.Controls"
         mc:Ignorable="d" DataContext="{Binding Mode=OneWay, RelativeSource={RelativeSource Self}}"
         d:DesignHeight="300" d:DesignWidth="300">

<Interactivity:Interaction.Behaviors>
    <Behaviors:ImportUsersOnLoadedBehavior />
</Interactivity:Interaction.Behaviors>
<DockPanel LastChildFill="True">
    <Label Content="账号" DockPanel.Dock="Top" FontSize="18.667" />

    <StackPanel Orientation="Horizontal" DockPanel.Dock="Bottom" HorizontalAlignment="Right">
        <Button x:Name="AddAccountButton" Height="26" Width="80" Content="添加" Margin="5" Command="{Binding AddUserCommand}" />
        <Button x:Name="ImportAccountsButton" Height="26" Width="80" Content="导入" Margin="5" Command="{Binding ImportUsersCommand}"/>
        <Button x:Name="DeleteAccountButton" Height="26" Width="80" Content="删除" Margin="5" Command="{Binding RemoveUsersCommand}"/>
    </StackPanel>

    <ListView x:Name="accountListbox" Margin="5" BorderThickness="1" BorderBrush="{DynamicResource AccentColorBrush}" ItemsSource="{Binding UsersCollection}"/>
</DockPanel>

代码隐藏

public partial class UsersControl : UserControl
{
    public static ObservableCollection<User> GetUsersCollection(DependencyObject obj)
    {
        return (ObservableCollection<User>)obj.GetValue(UsersCollectionProperty);
    }

    public static void SetUsersCollection(DependencyObject obj, ObservableCollection<User> value)
    {
        obj.SetValue(UsersCollectionProperty, value);
    }

    // Using a DependencyProperty as the backing store for UsersCollection.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty UsersCollectionProperty =
        DependencyProperty.RegisterAttached("UsersCollection", typeof(ObservableCollection<User>), typeof(UsersControl), new FrameworkPropertyMetadata(null,FrameworkPropertyMetadataOptions.AffectsRender));


}

我在 MainWindow.xaml 中使用了这个 UsersControl，并将 UsersCollection 绑定到主 windows 的 DataContext。

<Controls:MetroWindow x:Class="ZggwwDocuments.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:c="clr-namespace:Lloyd.Shared.Controls;assembly=Lloyd.Shared.Controls"
    xmlns:vm="clr-namespace:ZggwwDocuments.ViewModels"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:ZggwwDocuments"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="697.514">
<Controls:MetroWindow.DataContext>
    <vm:MainWindowViewModel/>
</Controls:MetroWindow.DataContext>
<Grid Margin="5">
    <c:UsersControl UsersCollection="{Binding Users}"  />
</Grid>

我在 MainWindow 上设置了断点，它的 DataContext 和 Users 属性不为空。但是 MainWindow.DataContext.Users 和 UsersControl.UsersCollection 之间的绑定失败了。以下是输出window

System.Windows.Data Error: 40 : BindingExpression path error: 'Users' property not found on 'object' ''UsersControl' (Name='userControl')'. BindingExpression:Path=Users; DataItem='UsersControl' (Name='userControl'); target element is 'UsersControl' (Name='userControl'); target property is 'UsersCollection' (type 'ObservableCollection`1')

UsersControl.xaml.cs 中的 GetUsersCollection(DependencyObject obj) 总是 return null

Answer 1

试着像下面这样给你的附件属性打电话：

<c:UsersControl UsersControl.UsersCollection="{Binding Users}"  />

Answer 2

尝试

ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type c:UsersControl}}, Path=UsersCollection}"

或者，你可以机灵点；

<DockPanel LastChildFill="True">
    <Label Content="账号" DockPanel.Dock="Top" FontSize="18.667" />

    <StackPanel Orientation="Horizontal" DockPanel.Dock="Bottom" HorizontalAlignment="Right">
        <Button x:Name="AddAccountButton" Height="26" Width="80" Content="添加" Margin="5" Command="{Binding AddUserCommand}" />
        <Button x:Name="ImportAccountsButton" Height="26" Width="80" Content="导入" Margin="5" Command="{Binding ImportUsersCommand}"/>
        <Button x:Name="DeleteAccountButton" Height="26" Width="80" Content="删除" Margin="5" Command="{Binding RemoveUsersCommand}"/>
    </StackPanel>

    <ListView x:Name="accountListbox" Margin="5" BorderThickness="1" BorderBrush="{DynamicResource AccentColorBrush}" ItemsSource="{Binding UsersCollection}"/>
</DockPanel>

...然后把它塞进去；

<UserControl.Template>
   <ControlTemplate TargetType="{x:Type UserControl}">
      (paste it here)
   </ControlTemplate>
</UserControl.Template>

然后将绑定更改为；

{Binding RelativeSource={RelativeSource TemplatedParent}, Path=UsersCollection}

我个人推荐这种方法而不是第一种方法，因为绑定更快，更不容易... 'issues'...而且这也意味着您要覆盖用户的模板控制成为您真正想要的样子，而不是仅仅在其现有模板中倾倒一些 XAML。

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附加属性绑定在我的用户控件中失败