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();// ListDragSourcethis.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);// ListDragTargetthis.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);// UseCustomCursorsCheckthis.UseCustomCursorsCheck.Location = new System.Drawing.Point(10, 243);this.UseCustomCursorsCheck.Size = new System.Drawing.Size(137, 24);this.UseCustomCursorsCheck.Text = "Use Custom Cursors";// DropLocationLabelthis.DropLocationLabel.Location = new System.Drawing.Point(154, 245);this.DropLocationLabel.Size = new System.Drawing.Size(137, 24);this.DropLocationLabel.Text = "None";// Form1this.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;elseCursor.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;}elsee.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);}elseDropLocationLabel.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);elseListDragTarget.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";}}}
