在DataTemplate中使用自定义控件时，绑定不起作用 [英] Binding doesn't work when using custom control in DataTemplate

问题描述

我试图用自定义控件替换ListView DataTemplate中的标准控件，但是绑定似乎无法正常工作。这是ListView的定义：

I'm trying to replace a standard control inside ListView DataTemplate with a custom control, but binding doesn't seem to work properly. Here is the definition of the ListView:

<Grid>
    <ListView ItemsSource="{Binding DataItemsCollection}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <TextBlock Text="Static text" />
                    <TextBlock Text="{Binding DataItemText}" />
                    <BindingTest:CustomControl CustomText="{Binding DataItemText}" />
                </StackPanel>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</Grid>

其中DataItemsCollection是可观察类型的集合

Where DataItemsCollection is an observable collection of type

public class DataItemClass : INotifyPropertyChanged
{
    string _dataItemText;
    public string DataItemText
    {
        get { return _dataItemText; }
        set { _dataItemText = value; Notify("DataItemText");  }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void Notify(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

主窗口代码如下：

public partial class MainWindow : Window
{
    public ObservableCollection<DataItemClass> _dataItemsCollection = new ObservableCollection<DataItemClass>
        { 
            new DataItemClass { DataItemText = "Test one" },
            new DataItemClass { DataItemText = "Test two" },
            new DataItemClass { DataItemText = "Test three" }
        };

    public ObservableCollection<DataItemClass> DataItemsCollection
    {
        get { return _dataItemsCollection; }
    }

    public MainWindow()
    {
        InitializeComponent();

        DataContext = this;
    }
}

自定义控件很简单：

<StackPanel Orientation="Horizontal">
    <Label Content="Data Item:" />
    <TextBlock Text="{Binding CustomText, Mode=OneWay}" />
</StackPanel>

CustomText定义为

With CustomText defined as

    public static DependencyProperty CustomTextProperty = DependencyProperty.Register(
        "CustomText", typeof(string), typeof(CustomControl), new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));

    public string CustomText
    {
        get { return (string)GetValue(CustomTextProperty); }
        set { SetValue(CustomTextProperty, value); }
    }

运行此项目时，我在DataTemplate的第二个TextBlock中看到正确的文本，但不在自定义控件内。我在做什么错？

When I run this project I see correct text in second TextBlock in DataTemplate, but not inside of a custom control. What am I doing wrong?

推荐答案

默认情况下 Binding 是相对于 DataContext ，在您的情况下为 DataItemClass ，但 CustomText 属性在 CustomControl 中声明。您需要指定相对绑定源：

By default Binding is relative to DataContext, which is DataItemClass in your case, but CustomText property is declared in CustomControl. You need to specify relative binding source:

<TextBlock Text="{Binding Path=CustomText,
                          RelativeSource={RelativeSource Mode=FindAncestor,
                                    AncestorType=BindingTest:CustomControl}}" />

如果您的控件将保持如此简单，则可以完全删除 CustomText 属性，然后将< TextBlock Text = {Binding CustomText，Mode = OneWay} /> 更改为 ; TextBlock Text = {Binding DataItemText} /> 。

If your control is going to stay that simple, you can completely remove CustomText property and change <TextBlock Text="{Binding CustomText, Mode=OneWay}" /> to just <TextBlock Text="{Binding DataItemText} />.

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