什么是事件传递给视图模型的最佳方式？ [英] What's the best way to pass event to ViewModel?

问题描述

目前，此案：我有我想要我的ViewModel反应对控件的事件。目前我通过执行隐形按钮的命令，就像下面的例子这样做。

The case is: I have a control's event that I want my ViewModel to react on. Currently I'm doing this by executing a command of invisible button like in the example below.

在View.xaml：

In View.xaml:

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

在View.xaml.cs：

In View.xaml.cs:

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

这个作品很好，但它看起来像一个黑客给我。我不知道是否有这样做的更好（标准）的方式？我找不到任何的例子，这就是我发明自己。

This works good, but it looks like a hack to me. I'm wondering if there is better (standard) way of doing this? I could not find any examples and this is what I "invented" myself.

推荐答案

使用MVVM，处理事件的一般方式是简单地将它们包装中的附加属性，或使用的附活动的。这里是附加属性使用 previewKeyDown 事件的例子：

Using MVVM, the general way to handle events is to simply wrap them in Attached Properties, or use Attached Events. Here is an example using the PreviewKeyDown event in an Attached Property:

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);
}

请注意，这也很容易（和更好了），以使用的ICommand ，而不是实际的 KeyEventArgs 对象不应该真正在视图模型。只要创建类型的附加属性的ICommand ，并呼吁从这个 TextBox_ previewKeyDown 处理程序来代替：

Note that it is just as easy (and better too) to use an ICommand instead of the actual KeyEventArgs object which shouldn't really be in the view model. Just create an Attached Property of type ICommand and call that from this TextBox_PreviewKeyDown handler instead:

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，它会使用这样的：

Either way, it would be used something like this:

<TextBox TextBoxProperties.PreviewKeyDown="SomeKeyEventHandler" />

或者，如果你使用的pferred $ P $ 的ICommand 方法：

<TextBox TextBoxProperties.PreviewKeyDownCommand="{Binding SomeCommand}" />

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