Drag&Drop ListView

using System;
using System.Drawing;
using System.Windows.Forms;

namespace Snip_DragNDrop
{
	public class Form1 : System.Windows.Forms.Form
	{
		private System.Windows.Forms.ListBox ListDragSource;
		private System.Windows.Forms.ListBox ListDragTarget;
		private System.Windows.Forms.CheckBox UseCustomCursorsCheck;
		private System.Windows.Forms.Label DropLocationLabel;

		private int indexOfItemUnderMouseToDrag;
		private int indexOfItemUnderMouseToDrop;

		private Rectangle dragBoxFromMouseDown;
		private Point screenOffset;

		private Cursor MyNoDropCursor;
		private Cursor MyNormalCursor;

		/// The main entry point for the application.
		[STAThread]
		static void Main()
		{
			Application.Run(new Form1());
		}

		public Form1()
		{
			this.ListDragSource = new System.Windows.Forms.ListBox();
			this.ListDragTarget = new System.Windows.Forms.ListBox();
			this.UseCustomCursorsCheck = new System.Windows.Forms.CheckBox();
			this.DropLocationLabel = new System.Windows.Forms.Label();

			this.SuspendLayout();

			// ListDragSource
			this.ListDragSource.Items.AddRange(new object[] {"one", "two", "three", "four", 
                                                                "five", "six", "seven", "eight",
                                                                "nine", "ten"});
			this.ListDragSource.Location = new System.Drawing.Point(10, 17);
			this.ListDragSource.Size = new System.Drawing.Size(120, 225);
			this.ListDragSource.MouseDown += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseDown);
			this.ListDragSource.QueryContinueDrag += new System.Windows.Forms.QueryContinueDragEventHandler(this.ListDragSource_QueryContinueDrag);
			this.ListDragSource.MouseUp += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseUp);
			this.ListDragSource.MouseMove += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseMove);
			this.ListDragSource.GiveFeedback += new System.Windows.Forms.GiveFeedbackEventHandler(this.ListDragSource_GiveFeedback);

			// ListDragTarget
			this.ListDragTarget.AllowDrop = true;
			this.ListDragTarget.Location = new System.Drawing.Point(154, 17);
			this.ListDragTarget.Size = new System.Drawing.Size(120, 225);
			this.ListDragTarget.DragOver += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragOver);
			this.ListDragTarget.DragDrop += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragDrop);
			this.ListDragTarget.DragEnter += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragEnter);
			this.ListDragTarget.DragLeave += new System.EventHandler(this.ListDragTarget_DragLeave);

			// UseCustomCursorsCheck
			this.UseCustomCursorsCheck.Location = new System.Drawing.Point(10, 243);
			this.UseCustomCursorsCheck.Size = new System.Drawing.Size(137, 24);
			this.UseCustomCursorsCheck.Text = "Use Custom Cursors";

			// DropLocationLabel
			this.DropLocationLabel.Location = new System.Drawing.Point(154, 245);
			this.DropLocationLabel.Size = new System.Drawing.Size(137, 24);
			this.DropLocationLabel.Text = "None";

			// Form1
			this.ClientSize = new System.Drawing.Size(292, 270);
			this.Controls.AddRange(new System.Windows.Forms.Control[] {this.ListDragSource,
                                                        this.ListDragTarget, this.UseCustomCursorsCheck,
                                                        this.DropLocationLabel});
			this.Text = "drag-and-drop Example";

			this.ResumeLayout(false);

		}

		private void ListDragSource_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
		{
			// Get the index of the item the mouse is below.
			indexOfItemUnderMouseToDrag = ListDragSource.IndexFromPoint(e.X, e.Y);

			if (indexOfItemUnderMouseToDrag != ListBox.NoMatches)
			{

				// Remember the point where the mouse down occurred. The DragSize indicates
				// the size that the mouse can move before a drag event should be started.                
				Size dragSize = SystemInformation.DragSize;

				// Create a rectangle using the DragSize, with the mouse position being
				// at the center of the rectangle.
				dragBoxFromMouseDown = new Rectangle(new Point(e.X - (dragSize.Width / 2),
															   e.Y - (dragSize.Height / 2)), dragSize);
			}
			else
				// Reset the rectangle if the mouse is not over an item in the ListBox.
				dragBoxFromMouseDown = Rectangle.Empty;

		}

		private void ListDragSource_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
		{
			// Reset the drag rectangle when the mouse button is raised.
			dragBoxFromMouseDown = Rectangle.Empty;
		}

		private void ListDragSource_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
		{

			if ((e.Button & MouseButtons.Left) == MouseButtons.Left)
			{

				// If the mouse moves outside the rectangle, start the drag.
				if (dragBoxFromMouseDown != Rectangle.Empty &&
					!dragBoxFromMouseDown.Contains(e.X, e.Y))
				{

					// Create custom cursors for the drag-and-drop operation.
					try
					{
						MyNormalCursor = new Cursor("3dwarro.cur");
						MyNoDropCursor = new Cursor("3dwno.cur");

					}
					catch
					{
						// An error occurred while attempting to load the cursors, so use
						// standard cursors.
						UseCustomCursorsCheck.Checked = false;
					}
					finally
					{

						// The screenOffset is used to account for any desktop bands 
						// that may be at the top or left side of the screen when 
						// determining when to cancel the drag drop operation.
						screenOffset = SystemInformation.WorkingArea.Location;

						// Proceed with the drag-and-drop, passing in the list item.                    
						DragDropEffects dropEffect = ListDragSource.DoDragDrop(ListDragSource.Items[indexOfItemUnderMouseToDrag], DragDropEffects.All | DragDropEffects.Link);

						// If the drag operation was a move then remove the item.
						if (dropEffect == DragDropEffects.Move)
						{
							ListDragSource.Items.RemoveAt(indexOfItemUnderMouseToDrag);

							// Selects the previous item in the list as long as the list has an item.
							if (indexOfItemUnderMouseToDrag > 0)
								ListDragSource.SelectedIndex = indexOfItemUnderMouseToDrag - 1;

							else if (ListDragSource.Items.Count > 0)
								// Selects the first item.
								ListDragSource.SelectedIndex = 0;
						}

						// Dispose of the cursors since they are no longer needed.
						if (MyNormalCursor != null)
							MyNormalCursor.Dispose();

						if (MyNoDropCursor != null)
							MyNoDropCursor.Dispose();
					}
				}
			}
		}

		private void ListDragSource_GiveFeedback(object sender, System.Windows.Forms.GiveFeedbackEventArgs e)
		{
			// Use custom cursors if the check box is checked.
			if (UseCustomCursorsCheck.Checked)
			{

				// Sets the custom cursor based upon the effect.
				e.UseDefaultCursors = false;
				if ((e.Effect & DragDropEffects.Move) == DragDropEffects.Move)
					Cursor.Current = MyNormalCursor;
				else
					Cursor.Current = MyNoDropCursor;
			}

		}

		private void ListDragTarget_DragOver(object sender, System.Windows.Forms.DragEventArgs e)
		{

			// Determine whether string data exists in the drop data. If not, then
			// the drop effect reflects that the drop cannot occur.
			if (!e.Data.GetDataPresent(typeof(System.String)))
			{

				e.Effect = DragDropEffects.None;
				DropLocationLabel.Text = "None - no string data.";
				return;
			}

			// Set the effect based upon the KeyState.
			if ((e.KeyState & (8 + 32)) == (8 + 32) &&
				(e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link)
			{
				// KeyState 8 + 32 = CTL + ALT

				// Link drag-and-drop effect.
				e.Effect = DragDropEffects.Link;

			}
			else if ((e.KeyState & 32) == 32 &&
				(e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link)
			{

				// ALT KeyState for link.
				e.Effect = DragDropEffects.Link;

			}
			else if ((e.KeyState & 4) == 4 &&
			  (e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)
			{

				// SHIFT KeyState for move.
				e.Effect = DragDropEffects.Move;

			}
			else if ((e.KeyState & 8) == 8 &&
			  (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy)
			{

				// CTL KeyState for 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;

			}
			else
				e.Effect = DragDropEffects.None;

			// Get the index of the item the mouse is below. 

			// The mouse locations are relative to the screen, so they must be 
			// converted to client coordinates.

			indexOfItemUnderMouseToDrop =
				ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(new Point(e.X, e.Y)));

			// Updates the label text.
			if (indexOfItemUnderMouseToDrop != ListBox.NoMatches)
			{

				DropLocationLabel.Text = "Drops before item #" + (indexOfItemUnderMouseToDrop + 1);
			}
			else
				DropLocationLabel.Text = "Drops at the end.";

		}

		private void ListDragTarget_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
		{
			// Ensure that the list item index is contained in the data.
			if (e.Data.GetDataPresent(typeof(System.String)))
			{

				Object item = (object)e.Data.GetData(typeof(System.String));

				// Perform drag-and-drop, depending upon the effect.
				if (e.Effect == DragDropEffects.Copy ||
					e.Effect == DragDropEffects.Move)
				{

					// Insert the item.
					if (indexOfItemUnderMouseToDrop != ListBox.NoMatches)
						ListDragTarget.Items.Insert(indexOfItemUnderMouseToDrop, item);
					else
						ListDragTarget.Items.Add(item);

				}
			}
			// Reset the label text.
			DropLocationLabel.Text = "None";
		}

		private void ListDragSource_QueryContinueDrag(object sender, System.Windows.Forms.QueryContinueDragEventArgs e)
		{
			// Cancel the drag if the mouse moves off the form.
			ListBox lb = sender as ListBox;

			if (lb != null)
			{

				Form f = lb.FindForm();

				// Cancel the drag if the mouse moves off the form. The screenOffset
				// takes into account any desktop bands that may be at the top or left
				// side of the screen.
				if (((Control.MousePosition.X - screenOffset.X) < f.DesktopBounds.Left) ||
					((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) ||
					((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) ||
					((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom))
				{

					e.Action = DragAction.Cancel;
				}
			}
		}

		private void ListDragTarget_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
		{
			// Reset the label text.
			DropLocationLabel.Text = "None";
		}

		private void ListDragTarget_DragLeave(object sender, System.EventArgs e)
		{
			// Reset the label text.
			DropLocationLabel.Text = "None";
		}
	}
}