在 Enter 键按下时绑定 TextBox [英] Bind TextBox on Enter-key press

问题描述

TextBox 上的默认数据绑定是 TwoWay，它仅在 TextBox 失去焦点时才将文本提交给属性.

The default databinding on TextBox is TwoWay and it commits the text to the property only when TextBox lost its focus.

当我按下 TextBox 上的 Enter 键时，是否有任何简单的 XAML 方法来进行数据绑定?我知道在后面的代码中很容易做到，但是想象一下这个 TextBox 是否在一些复杂的 DataTemplate 中.

Is there any easy XAML way to make the databinding happen when I press the Enter key on the TextBox?. I know it is pretty easy to do in the code behind, but imagine if this TextBox is inside some complex DataTemplate.

推荐答案

您可以通过创建一个 附加行为.

You can make yourself a pure XAML approach by creating an attached behaviour.

像这样:

public static class InputBindingsManager
{

    public static readonly DependencyProperty UpdatePropertySourceWhenEnterPressedProperty = DependencyProperty.RegisterAttached(
            "UpdatePropertySourceWhenEnterPressed", typeof(DependencyProperty), typeof(InputBindingsManager), new PropertyMetadata(null, OnUpdatePropertySourceWhenEnterPressedPropertyChanged));

    static InputBindingsManager()
    {

    }

    public static void SetUpdatePropertySourceWhenEnterPressed(DependencyObject dp, DependencyProperty value)
    {
        dp.SetValue(UpdatePropertySourceWhenEnterPressedProperty, value);
    }

    public static DependencyProperty GetUpdatePropertySourceWhenEnterPressed(DependencyObject dp)
    {
        return (DependencyProperty)dp.GetValue(UpdatePropertySourceWhenEnterPressedProperty);
    }

    private static void OnUpdatePropertySourceWhenEnterPressedPropertyChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
    {
        UIElement element = dp as UIElement;

        if (element == null)
        {
            return;
        }

        if (e.OldValue != null)
        {
            element.PreviewKeyDown -= HandlePreviewKeyDown;
        }

        if (e.NewValue != null)
        {
            element.PreviewKeyDown += new KeyEventHandler(HandlePreviewKeyDown);
        }
    }

    static void HandlePreviewKeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Enter)
        {
            DoUpdateSource(e.Source);
        }
    }

    static void DoUpdateSource(object source)
    {
        DependencyProperty property =
            GetUpdatePropertySourceWhenEnterPressed(source as DependencyObject);

        if (property == null)
        {
            return;
        }

        UIElement elt = source as UIElement;

        if (elt == null)
        {
            return;
        }

        BindingExpression binding = BindingOperations.GetBindingExpression(elt, property);

        if (binding != null)
        {
            binding.UpdateSource();
        }
    }
}

然后在您的 XAML 中，您将 InputBindingsManager.UpdatePropertySourceWhenEnterPressedProperty 属性设置为您想要在按下 Enter 键时更新的属性.像这样

Then in your XAML you set the InputBindingsManager.UpdatePropertySourceWhenEnterPressedProperty property to the one you want updating when the Enter key is pressed. Like this

<TextBox Name="itemNameTextBox"
         Text="{Binding Path=ItemName, UpdateSourceTrigger=PropertyChanged}"
         b:InputBindingsManager.UpdatePropertySourceWhenEnterPressed="TextBox.Text"/>

(您只需要确保在 XAML 文件的根元素中包含b"的 xmlns clr-namespace 引用，指向您将 InputBindingsManager 放入的命名空间.

(You just need to make sure to include an xmlns clr-namespace reference for "b" in the root element of your XAML file pointing to which ever namespace you put the InputBindingsManager in).

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