小编典典

将事件传递给ViewModel的最佳方法是什么?

c#

情况是:我有一个控件的事件,我想让我的ViewModel做出反应。目前,我正在通过执行不可见按钮的命令来执行此操作,如以下示例所示。

在View.xaml中:

<Control x:Name="SearchResultGrid" ... DataRefreshed="SearchResultRefreshed" />
<Button x:Name="SearchResultRefreshedButton" Visibility="Collapsed" Command="{Binding SearchResultRefreshedCommand}" />

在View.xaml.cs中:

private void SearchResultRefreshed(object sender, EventArgs e)
{
    if (SearchResultRefreshedButton.Command != null)
    {
        SearchResultRefreshedButton.Command.Execute(SearchResultGrid.ResultRowCount);
    }
}

这很好用,但对我来说似乎是hack。我想知道是否有更好的(标准)方法?我找不到任何示例,这就是我自己“发明”的。


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2020-05-19

共1个答案

小编典典

使用MVVM处理事件的一般方法是将它们简单地包装在Attached Properties中,或使用Attached
Events
。这是PreviewKeyDown在附加属性中使用事件的示例:

public static DependencyProperty PreviewKeyDownProperty = DependencyProperty.RegisterAttached("PreviewKeyDown", typeof(KeyEventHandler), typeof(TextBoxProperties), new UIPropertyMetadata(null, OnPreviewKeyDownChanged));

public static KeyEventHandler GetPreviewKeyDown(DependencyObject dependencyObject)
{
    return (KeyEventHandler)dependencyObject.GetValue(PreviewKeyDownProperty);
}

public static void SetPreviewKeyDown(DependencyObject dependencyObject, KeyEventHandler value)
{
    dependencyObject.SetValue(PreviewKeyDownProperty, value);
}

public static void OnPreviewKeyDownChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
{
    TextBox textBox = dependencyObject as TextBox;
    if (e.OldValue == null && e.NewValue != null) textBox.PreviewKeyDown += TextBox_PreviewKeyDown;
    else if (e.OldValue != null && e.NewValue == null) textBox.PreviewKeyDown -= TextBox_PreviewKeyDown;
}

private static void TextBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
    TextBox textBox = sender as TextBox;
    KeyEventHandler eventHandler = GetPreviewKeyDown(textBox);
    if (eventHandler != null) eventHandler(sender, e);
}

注意,使用a
ICommand代替实际KeyEventArgs对象(这实际上不是视图模型中的对象)同样容易(并且也更好)。只需创建类型的附加属性,ICommand然后从此TextBox_PreviewKeyDown处理程序中调用它即可:

private static void TextBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
    TextBox textBox = sender as TextBox;
    ICommand command = PreviewKeyDownCommand(textBox);
    if (command != null && command.CanExecute(textBox)) command.Execute(textBox);
}

无论哪种方式,都将使用如下所示的方式:

<TextBox TextBoxProperties.PreviewKeyDown="SomeKeyEventHandler" />

或者,如果您使用了首选ICommand方法:

<TextBox TextBoxProperties.PreviewKeyDownCommand="{Binding SomeCommand}" />
2020-05-19