小编典典

在Enter键上绑定文本框

c#

默认的数据绑定TextBoxTwoWay,仅当TextBox失去焦点时才将文本提交给属性。

当我按?Enter键时,是否有任何简单的XAML方法使数据绑定发生TextBox。我知道在后面的代码中很容易做到,但是请想象这TextBox是否在某种复杂的内部DataTemplate


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2020-05-19

共1个答案

小编典典

通过创建附加行为,可以使自己成为纯XAML方法。

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XAML中,将InputBindingsManager.UpdatePropertySourceWhenEnterPressedProperty属性设置为要在Enter按下键时更新的属性。像这样

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

(您只需要确保在XAML文件的根元素中包括对“ b”的xmlns clr-
namespace引用,指向您将InputBindingsManager放入的任何名称空间)。

2020-05-19