Question

我需要将此事件从用户控件移动到viewModel，我已阅读以下链接但不确定我得到它，因为命令是真还是假，我的问题是假设我有以下事件我应该如何将其更改为viewModel。

请协助，我真的卡住!!!!

http://blog.magnusmontin.net/2013/06/30/handling-events-in-an-mvvm-wpf-application/

     private void DropText_PreviewMouseDown(object sender, MouseButtonEventArgs e)
     {
         var textBox = (TextBox) sender;
         if (textBox == null) return;
         textBox.Focus();
         var dataObject = new DataObject((textBox).Text);
         dataObject.SetData(DragSource, sender);
         DragDrop.DoDragDrop(textBox, dataObject, DragDropEffects.Copy | DragDropEffects.Move);
     }



  <TextBox x:Name="Job"  
                    AcceptsReturn="True"
                    AllowDrop="True" 
                    PreviewMouseDown="DropText_PreviewMouseDown"
                    SelectionChanged="listbox_SelectionChanged"
                    HorizontalAlignment="Left" 





internal class RelayCommand : ICommand
{
    readonly Action _execute;
    readonly Func<bool> _canExecute;

    public RelayCommand(Action execute)
        : this(execute, null)
    {
    }

    public RelayCommand(Action execute, Func<bool> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");
        _execute = execute;
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute();
    }

    public event EventHandler CanExecuteChanged
    {
        add
        {
            if (_canExecute != null)
                CommandManager.RequerySuggested += value;
        }
        remove
        {
            if (_canExecute != null)
                CommandManager.RequerySuggested -= value;
        }
    }

    public void Execute(object parameter)
    {
        _execute();
    }

    public event EventHandler CanExecuteChange;
    public void RaiseCanExecuteChange()
        {
        if (CanExecuteChange != null)
            CanExecuteChange(this, new EventArgs());
        }

Answer 1

以下是您在xaml中定义事件触发器的示例。 PreviewMouseDownCommand和SelectionChangedCommand是需要在viewmodel中声明的RelayCommands。

<TextBox  x:Name="Job"  
          AcceptsReturn="True"
          AllowDrop="True" 
          HorizontalAlignment="Left"> 
          <i:Interaction.Triggers>
              <i:EventTrigger EventName="PreviewMouseDown" >
                  <i:InvokeCommandAction Command="{Binding PreviewMouseDownCommand}" />
              </i:EventTrigger>
              <i:EventTrigger EventName="SelectionChanged" >
                  <i:InvokeCommandAction Command="{Binding SelectionChangedCommand}" />
              </i:EventTrigger>
          </i:Interaction.Triggers>
</TextBox>

您需要对System.Windows.Interactivity的引用才能使用事件触发器。将其添加到窗口中的命名空间声明中：

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

将以下事件从用户控件更改为viewModel

1 个答案: