The following code will enable dragging ListView items and dropping in Explorer to generate files. Temporary files will be generated and deferred rendering will be used...
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.IO;
namespace WinFormDragNDropExplorer
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.ListView listView1;
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
System.Windows.Forms.ListViewItem listViewItem1 = new System.Windows.Forms.ListViewItem("Item 1");
System.Windows.Forms.ListViewItem listViewItem2 = new System.Windows.Forms.ListViewItem("Item 2");
System.Windows.Forms.ListViewItem listViewItem3 = new System.Windows.Forms.ListViewItem("Item 3");
this.listView1 = new System.Windows.Forms.ListView();
this.SuspendLayout();
//
// listView1
//
this.listView1.Items.AddRange(new System.Windows.Forms.ListViewItem[] {
listViewItem1,
listViewItem2,
listViewItem3});
this.listView1.Location = new System.Drawing.Point(40, 24);
this.listView1.Name = "listView1";
this.listView1.Size = new System.Drawing.Size(384, 280);
this.listView1.TabIndex = 0;
this.listView1.QueryContinueDrag += new System.Windows.Forms.QueryContinueDragEventHandler(this.listView1_QueryContinueDrag);
this.listView1.ItemDrag += new System.Windows.Forms.ItemDragEventHandler(this.listView1_ItemDrag);
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(472, 333);
this.Controls.Add(this.listView1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
#endregion
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
private ShellDataObject dataObj = null;
private void listView1_QueryContinueDrag(object sender, System.Windows.Forms.QueryContinueDragEventArgs e)
{
//ESC pressed
if (e.EscapePressed)
{
e.Action = DragAction.Cancel;
return;
}
//Drop!
if (e.KeyState == 0)
{
dataObj.SetData(ShellClipboardFormats.CFSTR_INDRAGLOOP, 0);
e.Action = DragAction.Drop;
return;
}
e.Action = DragAction.Continue;
}
private void listView1_ItemDrag(object sender, System.Windows.Forms.ItemDragEventArgs e)
{
String[] fileNames;
//Create the data object used for the drag drop operation
dataObj = new ShellDataObject();
//Create an array of strings to hold the filename(s)
fileNames = new String[listView1.SelectedItems.Count];
//Create temporary files that the user can drag.
for (int i = 0; i < listView1.SelectedItems.Count; i++)
{
fileNames[i] = CreateTemporaryFileName(listView1.SelectedItems[i].Text + ".txt");
}
//Add the list of files to the data object
dataObj.SetData(DataFormats.FileDrop, fileNames);
//Set the preferred drop effect
dataObj.SetData(ShellClipboardFormats.CFSTR_PREFERREDDROPEFFECT, DragDropEffects.Move);
//Indicate that we are in a drag loop
dataObj.SetData(ShellClipboardFormats.CFSTR_INDRAGLOOP, 1);
//Initiate the drag operation
listView1.DoDragDrop(dataObj, DragDropEffects.Move | DragDropEffects.Copy);
//Free the data object
dataObj = null;
}
private String CreateTemporaryFileName(String name)
{
String path;
String fileName;
System.IO.StreamWriter file;
//Build a path for the temporary file
path = System.IO.Path.GetTempPath();
fileName = System.IO.Path.Combine(path, name);
//Create the temporary file to make sure it exists
file = new System.IO.StreamWriter(fileName);
file.Close();
return fileName;
}
}
//Constant declarations. Please refer to "shlobj.h"
public class ShellClipboardFormats
{
public const string CFSTR_SHELLIDLIST = "Shell IDList Array";
public const string CFSTR_SHELLIDLISTOFFSET = "Shell Object Offsets";
public const string CFSTR_NETRESOURCES = "Net Resource";
public const string CFSTR_FILEDESCRIPTORA = "FileGroupDescriptor";
public const string CFSTR_FILEDESCRIPTORW = "FileGroupDescriptorW";
public const string CFSTR_FILECONTENTS = "FileContents";
public const string CFSTR_FILENAMEA = "FileName";
public const string CFSTR_FILENAMEW = "FileNameW";
public const string CFSTR_PRINTERGROUP = "PrinterFreindlyName";
public const string CFSTR_FILENAMEMAPA = "FileNameMap";
public const string CFSTR_FILENAMEMAPW = "FileNameMapW";
public const string CFSTR_SHELLURL = "UniformResourceLocator";
public const string CFSTR_INETURLA = CFSTR_SHELLURL;
public const string CFSTR_INETURLW = "UniformResourceLocatorW";
public const string CFSTR_PREFERREDDROPEFFECT = "Preferred DropEffect";
public const string CFSTR_PERFORMEDDROPEFFECT = "Performed DropEffect";
public const string CFSTR_PASTESUCCEEDED = "Paste Succeeded";
public const string CFSTR_INDRAGLOOP = "InShellDragLoop";
public const string CFSTR_DRAGCONTEXT = "DragContext";
public const string CFSTR_MOUNTEDVOLUME = "MountedVolume";
public const string CFSTR_PERSISTEDDATAOBJECT = "PersistedDataObject";
public const string CFSTR_TARGETCLSID = "TargetCLSID";
public const string CFSTR_LOGICALPERFORMEDDROPEFFECT = "Logical Performed DropEffect";
public const string CFSTR_AUTOPLAY_SHELLIDLISTS = "Autoplay Enumerated IDList Array";
}
public class ShellDataObject: DataObject
{
//This flag is used to prevent multiple callings to "GetData" when dropping in Explorer.
private bool downloaded = false;
public override object GetData(String format)
{
Object obj = base.GetData(format);
if (System.Windows.Forms.DataFormats.FileDrop == format &&
!InDragLoop() && !downloaded)
{
int i;
String[] files = (String[])obj;
for (i = 0; i < files.Length; i++)
{
DownloadFile(files[i]);
}
downloaded = true;
}
return obj;
}
private void DownloadFile(String filename)
{
StreamWriter file;
// Create the temporary file and its data
file = new StreamWriter(filename);
file.WriteLine(filename);
file.Close();
}
private bool InDragLoop()
{
return (0 != (int)GetData(ShellClipboardFormats.CFSTR_INDRAGLOOP));
}
}
}
