Drag multiple items from WPF listview

Question

I have a listview that displays files from a directory.
The user can drag each item in the listview to a folder/ the desktop and the associated file is copied there.
This works fine. The problem is- I want to do so for multiple items- so the user can select multiple listviewitems and drag and copy them together. The ListView is set to SelectedMode=Multiple- but it doesn't copy all of the selected items. Here's my code:

    private void FileView_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        this.start = e.GetPosition(null);
    }

    private void FileView_MouseMove(object sender, MouseEventArgs e)
    {
        Point mpos = e.GetPosition(null);
        Vector diff = this.start - mpos;

        if (e.LeftButton == MouseButtonState.Pressed &&
            Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance &&
            Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)
        {
            if (this.FileView.SelectedItems.Count == 0)
            {
                return;
            }

            // right about here you get the file urls of the selected items.  
            // should be quite easy, if not, ask.  
            string[] files = new String[1];
            files[0] = "C:\\Users\\MyName\\Music\\My playlist\\" + FileView.SelectedValue.ToString();
            string dataFormat = DataFormats.FileDrop;
            DataObject dataObject = new DataObject(dataFormat, files);
            DragDrop.DoDragDrop(this.FileView, dataObject, DragDropEffects.Copy);
        } 
    }

Thanks!

user2942457 · Accepted Answer · 2013-10-31 17:38:03Z

8

 private List<object> _selItems = new List<object>();
    private void FileView_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        this._start = e.GetPosition(null);
        _selItems.Clear();
        _selItems.AddRange(FileView.SelectedItems.Cast<object>());

    }

restore on MouseMove

foreach (object selItem in _selItems)
            {
                if (!FileView.SelectedItems.Contains(selItem))
                    FileView.SelectedItems.Add(selItem);
            }

answered Oct 31, 2013 at 17:38

user2942457

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1 Comment

user3557327 Over a year ago

Thanks for this, it's exactly what I was needing. The selection was changing to the one item under the cursor before I could grab all the selected items.

Ed Bayiates · Accepted Answer · 2018-03-26 19:14:07Z

The problem here is that you are using SelectedValue for a multiselect, so you get one file. What you want is something more like this:

private void FileView_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    this.start = e.GetPosition(null);
}

private void FileView_MouseMove(object sender, MouseEventArgs e)
{
    Point mpos = e.GetPosition(null);
    Vector diff = this.start - mpos;

    if (e.LeftButton == MouseButtonState.Pressed &&
        (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance ||
         Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)
    )
    {
        if (this.FileView.SelectedItems.Count == 0)
            return;

        // right about here you get the file urls of the selected items.  
        // should be quite easy, if not, ask.  
        string[] files = new String[FileView.SelectedItems.Count];
        int ix = 0;
        foreach (object nextSel in FileView.SelectedItems)
        {
            files[ix] = "C:\\Users\\MyName\\Music\\My playlist\\" + nextSel.ToString();
            ++ix;
        }
        string dataFormat = DataFormats.FileDrop;
        DataObject dataObject = new DataObject(dataFormat, files);
        DragDrop.DoDragDrop(this.FileView, dataObject, DragDropEffects.Copy);
    } 
}

shimpossible · Accepted Answer · 2013-04-24 00:35:15Z

3

I'd like to point out an small error in the code

    Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance &&
    Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)

should be

    Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance ||
    Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)

Otherwise a straight Horizontal or Vertical will do nothing. Chances of that happening are small, but still..

answered Apr 24, 2013 at 0:35

shimpossible

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1 Comment

Sten Petrov Over a year ago

... or use the Vector's Length property instead

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