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Drag and drop, cut/copy and paste files with Windows Explorer

, 9 May 2006
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This article describes how to implement file interaction with Windows Explorer

Drag and drop files into explorer

Introduction

Recently, I needed to implement drag and drop with the Windows Explorer, but all of the examples I could find were not quite what I wanted. I wanted bi-directional, and in C#. So I wrote one.

This sample project lists a folder full of files, and lets you drag and drop them into Explorer. You can also drag from Explorer into the sample, and you can use the Shift and Ctrl keys to modify the action, just like in Explorer.

You can also use the right click options for cut and paste. I discovered that it is not possible to receive notifications when someone pastes your files into another folder (thereby cutting them out of the folder you are displaying) to allow you to update the view. So, I implemented a simple file watcher to watch the displayed folder and refresh it if it changes.

Background

I found a couple of examples on MSDN for drag and drop, but not using files, but they were still useful (Performing Drag-and-Drop Operations and Control.DoDragDrop Method).

Also, there was a snippet for doing cut & paste, which was useful: How to Cut Files to the Clipboard Programmatically in C#?

Using the code

The sample is fairly self explanatory, I’ve tried to cut out any code that wasn’t showing stuff that was relevant.

To start a drag operation into Explorer, we implement the ItemDrag event from the Listview, which gets called after you drag an item more than a few pixels. We simply call DoDragDrop passing the files to be dragged wrapped in a DataObject. You don't really need to understand DataObject - it implements the IDataObject interface used in the communication.

/// <summary>
/// Called when we start dragging an item out of our listview
/// </summary>
private void listView1_ItemDrag(object sender, 
        System.Windows.Forms.ItemDragEventArgs e)
{
    string[] files = GetSelection();
    if(files != null)
    {
        DoDragDrop(new DataObject(DataFormats.FileDrop, files), 
                   DragDropEffects.Copy | 
                   DragDropEffects.Move /* | 
                   DragDropEffects.Link */);
        RefreshView();
    }
}

Then, during the drag operation, if the drag happens over your window, your DragOver method gets called. You have to tell the caller what would happen if the user drops on this location. You do this by setting e.Effect to the correct values:

/// <summary>
/// Called when someone drags something over our listview
/// </summary>
private void listView1_DragOver(object sender, 
        System.Windows.Forms.DragEventArgs e)
{
    // Determine whether file data exists in the drop data. If not, then
    // the drop effect reflects that the drop cannot occur.
    if (!e.Data.GetDataPresent(DataFormats.FileDrop)) 
    {
        e.Effect = DragDropEffects.None;
        return;
    }

    // Set the effect based upon the KeyState.
    if ((e.KeyState & SHIFT) == SHIFT && 
        (e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move) 
    {
        e.Effect = DragDropEffects.Move;

    } 
    else if ((e.KeyState & CTRL) == CTRL && 
        (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy) 
    {
        e.Effect = DragDropEffects.Copy;
    } 
    else if ((e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)  
    {
        // By default, the drop action should be move, if allowed.
        e.Effect = DragDropEffects.Move;

        // Implement the rather strange behaviour of explorer that if the disk
        // is different, then default to a COPY operation
        string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
        if (files.Length > 0 && !files[0].ToUpper().StartsWith(homeDisk) && 
                                        // Probably better ways to do this
        (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy) 
            e.Effect = DragDropEffects.Copy;
    } 
    else
        e.Effect = DragDropEffects.None;

    // This is an example of how to get the item under the mouse
    Point pt = listView1.PointToClient(new Point(e.X, e.Y));
    ListViewItem itemUnder = listView1.GetItemAt(pt.X, pt.Y);
}

Then, when the user actually releases the mouse, the DragDrop method gets called. Here, we actually do the cut or copy operation:

/// <summary>
/// Somebody dropped something on our listview - perform the action
/// </summary>
private void listView1_DragDrop(object sender, 
        System.Windows.Forms.DragEventArgs e)
{
    // Can only drop files, so check
    if (!e.Data.GetDataPresent(DataFormats.FileDrop)) 
    {
        return;
    }

    string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
    foreach (string file in files)
    {
        string dest = homeFolder + "\\" + Path.GetFileName(file);
        bool isFolder = Directory.Exists(file);
        bool isFile = File.Exists(file);
        if (!isFolder && !isFile)
        // Ignore if it doesn't exist
            continue;

        try
        {
            switch(e.Effect)
            {
                case DragDropEffects.Copy:
                    if(isFile)
                    // TODO: Need to handle folders
                        File.Copy(file, dest, false);
                    break;
                case DragDropEffects.Move:
                    if (isFile)
                        File.Move(file, dest);
                    break;
                case DragDropEffects.Link:
                // TODO: Need to handle links
                    break;
            }
        }
        catch(IOException ex)
        {
            MessageBox.Show(this, "Failed to perform the" + 
              " specified operation:\n\n" + ex.Message, 
              "File operation failed", MessageBoxButtons.OK, 
              MessageBoxIcon.Stop);
        }
    }

    RefreshView();
}

That's all there is to it! Well, actually, there is a little more. If you want to use custom cursors, you can implement GiveFeedback, and if you want to know when the drag leaves your window, you can implement QueryContinueDrag, but I left these out to keep the code clean.

Cut and paste turned out to be quite simple as well. On the cut or copy operation, you just put the filenames on the clipboard using our trusty DataObject class:

/// <summary>
/// Write files to clipboard (from
/// http://blogs.wdevs.com/idecember/
///      archive/2005/10/27/10979.aspx)
/// </summary>
/// <param name="cut">True if cut, false if copy</param>
void CopyToClipboard(bool cut)
{
    string[] files = GetSelection();
    if(files != null)
    {
        IDataObject data = new DataObject(DataFormats.FileDrop, files);
        MemoryStream memo = new MemoryStream(4);
        byte[] bytes = new byte[]{(byte)(cut ? 2 : 5), 0, 0, 0};
        memo.Write(bytes, 0, bytes.Length);
        data.SetData("Preferred DropEffect", memo);
        Clipboard.SetDataObject(data);
    }
}

And then on the paste (if someone pastes onto us), we do the reverse:

/// <summary>
/// Paste context menu option
/// </summary>
private void pasteMenuItem_Click(object sender, System.EventArgs e)
{
    IDataObject data = Clipboard.GetDataObject();
    if (!data.GetDataPresent(DataFormats.FileDrop))
        return;

    string[] files = (string[])
      data.GetData(DataFormats.FileDrop);
    MemoryStream stream = (MemoryStream)
      data.GetData("Preferred DropEffect", true);
    int flag = stream.ReadByte();
    if (flag != 2 && flag != 5)
        return;
    bool cut = (flag == 2);
    foreach (string file in files)
    {
        string dest = homeFolder + "\\" + 
                      Path.GetFileName(file);
        try
        {
            if(cut)
                File.Move(file, dest);
            else
                File.Copy(file, dest, false);
        }
        catch(IOException ex)
        {
            MessageBox.Show(this, "Failed to perform the" + 
                " specified operation:\n\n" + ex.Message, 
                "File operation failed", 
                MessageBoxButtons.OK, MessageBoxIcon.Stop);
        }
    }

    RefreshView();
}

Points of interest

The most annoying thing was that if you cut from the sample and paste into Explorer, Explorer will move the files for you and take them out of your folder. However, there is no way to get a notification when this paste happens, so it is impossible to keep your view of the files up to date. I implemented a small file watcher which watches the sample folder, but I imagine this could get much more complicated if you need to watch many folders.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Paul Tallett
Web Developer
Europe Europe
I am a principal development consultant at Microsoft in the UK specialising in UI development. Recently I've been doing a lot of WPF work including the BBC iMP project shown at MIX06. I've been developing software for over 20 years - VAX, WIN16, MFC, ASP.NET, WinForms, WPF.
 
My main hobby is cars and my favourite day out is at Thruxton race track driving the Porsche 911 Turbo.

Comments and Discussions

 
QuestionOverwrite dialog goes behind PinmemberMember 104559409-Dec-13 19:35 
QuestionHow to change the behaviour of the drop event based on the target. Pinmemberextra_brain20-Apr-13 6:04 
Questiongreat article thanks Pinmemberdheerajv5-Jul-12 23:46 
GeneralMaking it work in Windows 7 PinmemberDanielRose198112-Jul-10 2:59 
GeneralRe: Making it work in Windows 7 PinmemberPandele Florin18-Apr-11 8:26 
QuestionHow to paste standard file to the disk from Clipboard Pinmembergihanatt15-Apr-10 14:39 
QuestionNeed help Pinmemberkayru31-Mar-10 1:18 
GeneralAwesome App Pinmembernoka0327-Nov-09 18:31 
GeneralWondering how to do this... Pinmembern13ldo15-Aug-09 4:09 
GeneralRe: Wondering how to do this... PinmemberXmen W.K.16-Mar-12 5:39 
QuestionHow to WPF? Pinmemberwetsnow12-Feb-09 9:21 
GeneralThanks for this PinmemberRick Hansen25-Aug-08 11:45 
Answerto refresh the list after cut Pinmemberasdfwefwef14-Jul-08 7:26 
GeneralDrag Drop PinmemberKaurGurpreet21-Nov-07 1:05 
GeneralVery useful Pinmembersrelu24-Oct-07 0:34 
GeneralRe: Very useful PinmemberJoachimBlaurock11-Feb-08 1:31 
Generaljust make control droppable area Pinmemberviki3d2-Jul-07 10:01 
GeneralSame folder problem PinmemberZeeshan Shigri26-May-07 6:16 
AnswerRe: Same folder problem PinmemberAurican31-Aug-07 13:46 
GeneralRe: Same folder problem Pinmembersrelu24-Oct-07 0:53 
GeneralRe: Same folder problem PinmemberZeeshan Shigri24-Oct-07 1:08 
GeneralCopy Paste in vb.net windows application Pinmemberbalamurugan8216-Apr-07 8:36 
GeneralRe: Copy Paste in vb.net windows application Pinmembersrelu24-Oct-07 1:27 
GeneralSource file location is uknown Pinmembervmo3d21-Feb-07 15:03 
AnswerRe: Source file location is uknown PinmemberAurican31-Aug-07 13:42 

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