ListBox WPF中的条件绑定

Question

I have a listbox in which drag and drop is implemented. I have bound SelectedItem and SelectedIndex properties. The SelectedItem and SelectedIndex properties gets set whenever there is a mouse down event. How do I prevent it from getting set when there only is a drag and drop operation? I tried overiding the previewleftbuttondown but found no success. Any ideas? I need some thing like:

       TimeSpan difference = DateTime.Now - mousePressedTime;

        if (difference.TotalSeconds >= 3)
        {
            // long press
            //SelectedIndex  and SelectedItem should not be set.
        }
        else
        {
            // short press
            //SelectedIndex  and SelectedItem should be set.
        }

Answer 1

I found a solution finally. But I couldn't do anything with the binding. What I did was I created my own Listbox and hooked the PreviewMouseLeftButtonDown and PreviewMouseLeftButtonUp events. What ever logic I was executing in the SelectedItem and SelectedIndex properties of the listbox, I had to move it some where else. The code is as follows, hope it gives a better idea:

 public class DragDropListBox : ListBox
 {
    private static DateTime mousePressedTime;

    public DragDropListBox()
    {
      this.PreviewMouseLeftButtonDown += PreviewMouseLeftButtonDownHandler;
      this.PreviewMouseLeftButtonUp   += PreviewMouseLeftButtonUpHandler;
    }

    private void PreviewMouseLeftButtonDownHandler(object sender, MouseButtonEventArgs e)
    {
      mousePressedTime    = DateTime.Now;
    }

    private void PreviewMouseLeftButtonUpHandler(object sender, MouseButtonEventArgs e)
    {
      TimeSpan difference = DateTime.Now - mousePressedTime;

      if (difference.TotalSeconds <= 1)
      {
        // short press
        if (SelectedItem != null)
        {
            // do what ever you have to
        }
      }
      UnselectAll();
    }
 }