Wpf MVVM 如何处理TextBox“粘贴事件"在视图模型中 [英] Wpf MVVM How to handle TextBox "paste event" in the ViewModel

问题描述

我使用 MVVM 模式开发应用程序.我使用 MVVMLight 库来做到这一点.所以如果我需要处理 TextBox TextChange 事件，我用 XAML 编写:

I develop application with using MVVM pattern. I using MVVMLight library to do this. So if I need to handle TextBox TextChange event I write in XAML:

<I:EventTrigger EventName="TextChanged">
    <I:InvokeCommandAction Command="{Binding PropertyGridTextChange}"/>
</I:EventTrigger>

其中 PropertyGridTextChange 是 ViewModel 中的 Command.但是 TextBox 没有 Paste 事件！

where PropertyGridTextChange is Command in ViewModel. But TextBox has no Paste event!

此 解决方案仅适用于应用程序不使用 MVVM 模式的情况，因为您需要在 TextBox 上添加链接.

This solution only works if application don't use MVVM pattern, because you need to have link on TextBox.

<DataTemplate x:Key="StringTemplate">
    <TextBox Text="{Binding Value, ValidatesOnDataErrors=True, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
    </TextBox>
</DataTemplate>

重要细节 - TextBox 放置在 DataTemplate 中.我不知道如何处理粘贴事件".我希望在将文本粘贴到 TextBox 时调用 PasteCommand.我需要将 TextBox.Text 或 TextBox 本身作为参数传递给 PasteCommandMethod.

Important detail - TextBox placed within DataTemplate. I have no idea how can I handle "paste event". I want PasteCommand to be invoked when I paste text into TextBox. And I need that TextBox.Text or TextBox itself to be passed as parameter into PasteCommandMethod.

private RelayCommand<Object> _pasteCommand;
public RelayCommand<Object> PasteCommand
{
    get
    {
        return _pasteCommand ?? (_pasteCommand =
            new RelayCommand<Object>(PasteCommandMethod));
    }
}

private void PasteCommandMethod(Object obj)
{
} 

推荐答案

我可以建议我的问题的答案.

I can suggest answer on my question.

班级助手.

public class TextBoxPasteBehavior 
{
public static readonly DependencyProperty PasteCommandProperty =
    DependencyProperty.RegisterAttached(
        "PasteCommand",
        typeof(ICommand),
        typeof(TextBoxPasteBehavior),
        new FrameworkPropertyMetadata(PasteCommandChanged)
    );

public static ICommand GetPasteCommand(DependencyObject target)
{
    return (ICommand)target.GetValue(PasteCommandProperty);
}

public static void SetPasteCommand(DependencyObject target, ICommand value)
{
    target.SetValue(PasteCommandProperty, value);
}

static void PasteCommandChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
    var textBox = (TextBox)sender;
    var newValue = (ICommand)e.NewValue;

    if (newValue != null)
        textBox.AddHandler(CommandManager.ExecutedEvent, new RoutedEventHandler(CommandExecuted), true);
    else
        textBox.RemoveHandler(CommandManager.ExecutedEvent, new RoutedEventHandler(CommandExecuted));

}

static void CommandExecuted(object sender, RoutedEventArgs e)
{
    if (((ExecutedRoutedEventArgs)e).Command != ApplicationCommands.Paste) return;

    var textBox = (TextBox)sender;
    var command = GetPasteCommand(textBox);

    if (command.CanExecute(null))
        command.Execute(textBox);
}
}

在 XAML 中使用.在 TextBox 中作为属性.

TextBoxPasteBehavior.PasteCommand="{Binding PropertyGridTextPasted}"

PropertyGridTextPasted - ViewModel 中的命令.

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