DataContext与ContentProperty的传递

Question

我想创建一个自定义控件来简化以下代码：

<StackPanel>
    <DockPanel LastChildFill="True">
        <Label>First Name</Label>
        <TextBox Margin="2" Text="{Binding Path=FirstName}"></TextBox>
    </DockPanel>
    <DockPanel LastChildFill="True">
        <Label>Last Name</Label>
        <TextBox Margin="2" Text="{Binding Path=LastName}"></TextBox>
    </DockPanel>
</StackPanel>

我的想法是像下面这样制作一个UserControl (布局有点不同，但超出了范围)：

<UserControl x:Class="LabelControl"
             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">
    <DockPanel LastChildFill="True">
        <Label Content="{Binding Path=Text}" Margin="2" MinWidth="100" HorizontalContentAlignment="Right"></Label>
        <Grid Margin="2">
            <ContentControl Content="{Binding Path=Control}" ></ContentControl>
        </Grid>
    </DockPanel>
</UserControl>

后面的代码公开了两个依赖项属性：

• 文本:标签的内容
• 控件:要由内容承载的控件。该类使用ContentProperty属性将子级映射到ContentControl。

这样我就可以简化我的StackPanel

<StackPanel>
    <controls:LabelControl Text="First Name">
        <TextBox Text="{Binding Path=FirstName}"></TextBox>
    </controls:LabelControl>
    <controls:LabelControl Text="Last Name">
        <TextBox Text="{Binding Path=LastName}"></TextBox>
    </controls:LabelControl>
</StackPanel>

我正在运行的问题是控件中的绑定不是映射。有办法绕过这件事吗？标签控件DataContext正在覆盖父控件上下文。

下面是LabelControl的代码：

[ContentProperty("Control")]
public partial class LabelControl : UserControl
{
    public static readonly DependencyProperty TextProperty = DependencyProperty.Register(
        "Text", typeof(string), typeof(LabelControl), new PropertyMetadata(default(string)));

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

    public static readonly DependencyProperty ControlProperty =
        DependencyProperty.Register("Control", typeof(Control), typeof(LabelControl), new PropertyMetadata(default(Control)));

    public Control Control
    {
        get { return (Control)GetValue(ControlProperty); }
        set { SetValue(ControlProperty, value); }
    }

    public LabelControl()
    {
        InitializeComponent();
        this.DataContext = this;
    }
}

编辑:输出确认数据文本正在重写。

BindingExpression path error: 'FirstName' property not found on 'object' ''LabelControl' (Name='')'. BindingExpression:Path=FirstName; DataItem='LabelControl' (Name=''); target element is 'TextBox' (Name=''); target property is 'Text' (type 'String')

Answer 1

如果您的LabelControl包含在Window中，并且它的DataContext具有FirstName属性，请尝试像这样更改绑定。

<TextBox Text="{Binding Path=FirstName, 
                RelativeSource={RelativeSource AncestorType=Window}}">
</TextBox>

如果您不想每次指定RelativeSource，您可以像现在一样使用LabelControl .

<StackPanel>
    <controls:LabelControl Text="First Name">
        <TextBox Text="{Binding Path=FirstName}"></TextBox>
    </controls:LabelControl>
    <controls:LabelControl Text="Last Name">
        <TextBox Text="{Binding Path=LastName}"></TextBox>
    </controls:LabelControl>
</StackPanel>

...and将更改LabelControl的实现。

首先，从DataContext的代码背后释放LabelControl分配。

public LabelControl()
{
    InitializeComponent();
    //this.DataContext = this; // we don't want this
}

然后将XAML模板更改为

<DockPanel LastChildFill="True">
    <Label Content="{Binding Path=Text,
           RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}" 
           Margin="2" MinWidth="100" HorizontalContentAlignment="Right">
    </Label>
    <Grid Margin="2">
        <ContentControl 
            Content="{Binding Path=Control, 
            RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}">
        </ContentControl>
    </Grid>
</DockPanel>

现在您应该正确设置您的DataContext。

Answer 2

我发现使用UserControl不是最理想的解决方案。事实证明，模板化控件允许DataBinds在没有任何黑客(RelativeSource)的情况下通过。

[ContentProperty("Control")]
public class LabelControl : Control
{

    public static readonly DependencyProperty TextProperty = DependencyProperty.Register("Text", 
        typeof(string), typeof(LabelControl), new PropertyMetadata(default(string)));

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

    public static readonly DependencyProperty ControlProperty =
        DependencyProperty.Register("Control", typeof(Control), typeof(LabelControl), new PropertyMetadata(default(Control)));

    public Control Control
    {
        get { return (Control)GetValue(ControlProperty); }
        set { SetValue(ControlProperty, value); }
    }
}

在app.xaml中：

<Style TargetType="controls:LabelControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="controls:LabelControl">
                <DockPanel LastChildFill="True">
                    <Label Content="{TemplateBinding Text}"  MinWidth="100" FontSize="11"></Label>
                    <Grid Margin="2">
                        <ContentControl Content="{TemplateBinding Control}"></ContentControl>
                    </Grid>
                </DockPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>