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。
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:
PreviewKeyDown
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:
ICommand
KeyEventArgs
TextBox_PreviewKeyDown
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}" />