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在类库中的定义为:  。

复制代码代码如下

[UIPermissionAttribute(SecurityAction.Demand, Clipboard = UIPermissionClipboard.OwnClipboard)]  public DragDropEffects DoDragDrop(  Object data,  DragDropEffects allowedEffects  )  。

其中data参数为要拖放的数据，如果拖动操作需要于另一个进程的应用程序相互操作，data代表的数据应该是基本托管类(String,BitMap,或MetaFile),或者是实现 ISerializable 或IDataObject的对象。 allowedEffects参数表示拖放的效果，为一个枚举值（DragDropEffects）.返回值也为DragDropEffects枚举值。  　　当开始调用DoDragDrop方法拖动一个数据对象时，DoDragDrops在拖放过程中，检测当前光标位置下的控件是不是有效的放置目标。如果当前光标下的控件是有效的放置目标，则GiveFeedBack事件以指定的拖放效果引发。在检测当前位置光标是否为有效的拖放目标时，DoDragDrops方法同时跟踪光标位置，键盘状态和鼠标状态的更改。  　　 (1)如果用于移出了一个窗口，则引发DragLeave事件。  　 （2）如果移入了另外一个控件，则引发该控件的DragEnter事件。  　　（3）如果鼠标移动，但是停留在一个控件中，则引发DragOver事件。  如果检测到更改了键盘或者鼠标状态,则引发拖放源的QueryContinueDrag事件, 并根据事件的QueryContinueDragEventArgs的Action属性值确定继续拖动，放置数据或取消操作。  （1）如果Action属性指定为Continue，则将引发DragOver事件。  (2)如果Action属性指定为Drop，则将放置效果返回给源，以便应用程序对数据进行适当的操作；例如，如果是移动操作，则剪切数据。  (3)如果是DragAction的值为Cancel,则引发DragLeave事件  从csdn上摘抄一段示例代码:  　　下面的代码示例演示在两个 ListBox 控件之间的拖放操作。当拖动动作启动时，该示例调用 DoDragDrop 方法。在 MouseDown 事件期间，如果从鼠标位置起鼠标移动的距离大于 SystemInformation..::.DragSize，则启动拖动动作。IndexFromPoint 方法用于确定在 MouseDown 事件期间要拖动的项的索引。  　　该示例还演示如何对拖放操作使用自定义光标。该示例要求应用程序目录中存在两个光标文件：3dwarro.cur 和 3dwno.cur，分别用于自定义拖动光标和禁止停放光标。如果选中 UseCustomCursorsCheckCheckBox，则使用自定义光标。自定义光标在 GiveFeedback 事件处理程序中设置。  　　键盘状态在右 ListBox 的 DragOver 事件处理程序中计算，以确定基于 Shift、Ctrl、Alt 或 Ctrl+Alt 键的状态将发生哪种拖动操作。放置动作在 ListBox 中发生的位置也在 DragOver 事件期间确定。如果要放置的数据不是 String，则 DragDropEffects 中将把 DragEventArgs.sEffect 设置为 None。最后，停放状态在 DropLocationLabelLabel 中显示。  　　要放置的用于右 ListBox 的数据在 DragDrop 事件处理程序中确定，并且在 ListBox 中的适当位置添加该 String 值。如果拖动操作移动到窗体边框的外面，则 QueryContinueDrag 事件处理程序中将取消拖放操作  。

复制代码代码如下

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";  }  }  }  。

对用这种拖放操作和微软的服务，容器模式的关系，留在以后再学习.

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