c# - Prism + MVVM + Access Keys + UpdateSourceTrigger="LostFocus" -- This doesn't let me save an updated textbox without first losing focus

Question

Not really sure how to tackle this issue:

I have a "Save" button that has access keys attached to it... but, if I type something into a textbox and press the access keys to save, the textbox doesn't update my viewmodel because it never lost focus. Any way to solve this outside of changing the UpdateSourceTrigger to PropertyChanged?

Answer 1

你的问题是UpdateSourceTrigger="LostFocus"

这是 TextBox 的默认设置，这意味着 TextBox 只会在失去焦点时更新其绑定值

强制它在不设置的情况下更新的一种方法UpdateSourceTrigger="PropertyChanged"是挂钩 KeyPress 事件，如果组合键会触发保存，UpdateSource()请先调用

这是我喜欢在 Enter 键更新源时使用的附加属性。

它是这样使用的：

<TextBox Text="{Binding Name}" 
         local:TextBoxProperties.EnterUpdatesTextSource="True" />

附加属性定义如下所示：

public class TextBoxProperties
{
    public static readonly DependencyProperty EnterUpdatesTextSourceProperty =
        DependencyProperty.RegisterAttached("EnterUpdatesTextSource", typeof(bool), typeof(TextBoxProperties), 
            new PropertyMetadata(false, EnterUpdatesTextSourcePropertyChanged));

    // Get
    public static bool GetEnterUpdatesTextSource(DependencyObject obj)
    {
        return (bool)obj.GetValue(EnterUpdatesTextSourceProperty);
    }

    // Set
    public static void SetEnterUpdatesTextSource(DependencyObject obj, bool value)
    {
        obj.SetValue(EnterUpdatesTextSourceProperty, value);
    }

    // Changed Event - Attach PreviewKeyDown handler
    private static void EnterUpdatesTextSourcePropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        var sender = obj as UIElement;
        if (obj != null)
        {
            if ((bool)e.NewValue)
            {
                sender.PreviewKeyDown += OnPreviewKeyDown_UpdateSourceIfEnter;
            }
            else
            {
                sender.PreviewKeyDown -= OnPreviewKeyDown_UpdateSourceIfEnter;
            }
        }
    }

    // If key being pressed is the Enter key, and EnterUpdatesTextSource is set to true, then update source for Text property
    private static void OnPreviewKeyDown_UpdateSourceIfEnter(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Enter)
        {
            if (GetEnterUpdatesTextSource((DependencyObject)sender))
            {
                var obj = sender as UIElement;
                BindingExpression textBinding = BindingOperations.GetBindingExpression(
                    obj, TextBox.TextProperty);

                if (textBinding != null)
                    textBinding.UpdateSource();
            }
        }
    }
}