数据绑定到 WPF 中的 UserControl - 无法取回值

Question

我有一个 UserControl，我想在其中实现数据绑定。我只是无法将输入返回到绑定。

用户控件：

<UserControl x:Class="WPFLibrary.UserControls.LabeledTextBox"
             x:Name="root" ... >
    <StackPanel  Orientation="Horizontal" Width="270" Height="30">
        <Label Content="LabelNotDef" Width="100" Name="BaseLabel" 
               HorizontalAlignment="Left" HorizontalContentAlignment="Left" VerticalContentAlignment="Top" />
        <TextBox Margin="0,0,20,0" Name="BaseTextBox" Width="150" Height="25" VerticalContentAlignment="Center" 
                 Text="{Binding ElementName=root, Path=Text2, UpdateSourceTrigger=PropertyChanged}" />
    </StackPanel>
</UserControl>

用户控件的隐藏代码：

public partial class LabeledTextBox : UserControl, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public static DependencyProperty TextProperty = DependencyProperty.Register("Text2", typeof(string), typeof(EffLabeledTextBox),
                                                                                 new PropertyMetadata(string.Empty, OnTextPropertyChanged));

    [Browsable(true)]
    public string Text2
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    private static void OnTextPropertyChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
    {
        EffLabeledTextBox myUserControl = dependencyObject as EffLabeledTextBox;
        myUserControl.OnPropertyChanged("Text2");
        myUserControl.OnTextPropertyChanged(e);
    }
    private void OnTextPropertyChanged(DependencyPropertyChangedEventArgs e)
    {
        BaseTextBox.Text = Text2;
    }

    public LabeledTextBox()
    {
        InitializeComponent();
    }
}

在另一个 UserControl 中实现：

<uCon:LabeledTextBox x:Name="Toastbread" Tabelle="artikel" Feld="nr" Text2="{Binding _strNR, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

代码隐藏：

public partial class ArtikelSearch : UserControl
{
    ArtikelSearchVM objVM;

    public ArtikelSearch()
    {
        InitializeComponent();
        objVM = new ArtikelSearchVM();
        this.DataContext = objVM;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        string a23 = Toastbread.Text2;
        string a24 = Toastbread.BaseTextBox.Text;
        System.Diagnostics.Debugger.Break();
        objVM.Suche();
    }
}

当我在文本字段中输入内容时触发 PropertyChanged。如果我检查 Toastbread.Text2，我会得到值。如果我检查 Toastbread.BaseTextBox.Text 我得到值。但是如果我检查 objVM._strNR 我只会得到 null。

当我在 ArtikelSearchVM 构造函数的 objVM._strNR 上手动设置一个值时，它在框中，但我也没有从文本框中取回修改后的值。

Answer 1

您无需在 UserControl 中实现 INotifyPropertyChanged。这就是您所需要的：

public partial class LabelTextBox : UserControl
{
    public LabelTextBox()
    {
        InitializeComponent();
    }

    public static DependencyProperty TextProperty = DependencyProperty.Register(
        nameof(Text), typeof(string), typeof(LabelTextBox));

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

像这样 XAML：

<UserControl ...>
    ...
    <TextBox Text="{Binding RelativeSource={RelativeSource AncestorType=UserControl},
                    Path=Text, UpdateSourceTrigger=PropertyChanged}" .../>
    ...
</UserControl>

您也可以考虑使 Text 属性默认双向绑定：

public static DependencyProperty TextProperty = DependencyProperty.Register(
    nameof(Text), typeof(string), typeof(LabelTextBox),
    new FrameworkPropertyMetadata(string.Empty,
        FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));

数据绑定到 WPF 中的 UserControl - 无法取回值

Data binding to a UserControl in WPF - cant get Value back

c#

wpf

user-controls

dependency-properties

inotifypropertychanged