Control.DoDragDrop 方法
开始拖放操作。
**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms（在 system.windows.forms.dll 中）
语法
声明
Public Function DoDragDrop ( _
data As Object, _
allowedEffects As DragDropEffects _
) As DragDropEffects
用法
Dim instance As Control
Dim data As Object
Dim allowedEffects As DragDropEffects
Dim returnValue As DragDropEffects
returnValue = instance.DoDragDrop(data, allowedEffects)
public DragDropEffects DoDragDrop (
Object data,
DragDropEffects allowedEffects
)
public:
DragDropEffects DoDragDrop (
Object^ data,
DragDropEffects allowedEffects
)
public DragDropEffects DoDragDrop (
Object data,
DragDropEffects allowedEffects
)
public function DoDragDrop (
data : Object,
allowedEffects : DragDropEffects
) : DragDropEffects
参数
- data
要拖动的数据。
- allowedEffects
DragDropEffects 值之一。
返回值
DragDropEffects 枚举的值，它表示在拖放操作期间执行的最终效果。
备注
allowedEffects 参数确定哪些拖动操作可以发生。如果拖动操作需要与另一个进程中的应用程序交互操作，数据应是基本托管类（String、Bitmap 或 Metafile），或实现 ISerializable 或 IDataObject 的对象。
下面描述与拖放操作相关的事件的引发方式以及引发时间。
DoDragDrop 方法确定当前光标位置下的控件。然后它将检查该控件是否是有效的放置目标。
如果该控件是有效的放置目标，则 GiveFeedback 事件以指定的拖放效果引发。有关拖放效果的列表，请参阅 DragDropEffects 枚举。
跟踪鼠标光标位置、键盘状态和鼠标按钮状态的更改。
如果更改了键盘或鼠标按钮状态，则引发 QueryContinueDrag 事件并根据事件的 QueryContinueDragEventArgs 的 Action 属性值确定是否继续拖动、放置数据或取消操作。
如果 DragAction 的值为 Continue，将引发 DragOver 事件以继续该操作，并引发 GiveFeedback 事件，同时产生新效果，以便能够设置适当的可视反馈。有关有效放置效果的列表，请参见 DragDropEffects 枚举。
提示
DragOver 和 GiveFeedback 事件成对出现，从而当鼠标从放置目标上移动时，就能够为用户提供有关鼠标位置的最新反馈。
如果 DragAction 的值为 Drop，放置效果值将恢复成源值，以便源应用程序可以对源数据执行适当的操作；例如，如果是移动操作，则剪切数据。
如果 DragAction 的值为 Cancel，将引发 DragLeave 事件。
示例
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 方法用于在 MouseDown 事件期间确定要拖动的项的索引。
该示例同时演示了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.Effect 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。
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Public NotInheritable Class Form1
Inherits System.Windows.Forms.Form
Friend WithEvents ListDragSource As System.Windows.Forms.ListBox
Friend WithEvents ListDragTarget As System.Windows.Forms.ListBox
Friend WithEvents UseCustomCursorsCheck As System.Windows.Forms.CheckBox
Friend WithEvents DropLocationLabel As System.Windows.Forms.Label
Private indexOfItemUnderMouseToDrag As Integer
Private indexOfItemUnderMouseToDrop As Integer
Private dragBoxFromMouseDown As Rectangle
Private screenOffset as Point
Private MyNoDropCursor As Cursor
Private MyNormalCursor As Cursor
<System.STAThread()> _
Public Shared Sub Main()
System.Windows.Forms.Application.Run(New Form1())
End Sub 'Main
Public Sub New()
MyBase.New()
Me.ListDragSource = New System.Windows.Forms.ListBox()
Me.ListDragTarget = New System.Windows.Forms.ListBox()
Me.UseCustomCursorsCheck = New System.Windows.Forms.CheckBox()
Me.DropLocationLabel = New System.Windows.Forms.Label()
Me.SuspendLayout()
' ListDragSource
Me.ListDragSource.Items.AddRange(New Object() {"one", "two", "three", "four", _
"five", "six", "seven", "eight", _
"nine", "ten"})
Me.ListDragSource.Location = New System.Drawing.Point(10, 17)
Me.ListDragSource.Size = New System.Drawing.Size(120, 225)
' ListDragTarget
Me.ListDragTarget.AllowDrop = True
Me.ListDragTarget.Location = New System.Drawing.Point(154, 17)
Me.ListDragTarget.Size = New System.Drawing.Size(120, 225)
' UseCustomCursorsCheck
Me.UseCustomCursorsCheck.Location = New System.Drawing.Point(10, 243)
Me.UseCustomCursorsCheck.Size = New System.Drawing.Size(137, 24)
Me.UseCustomCursorsCheck.Text = "Use Custom Cursors"
' DropLocationLabel
Me.DropLocationLabel.Location = New System.Drawing.Point(154, 245)
Me.DropLocationLabel.Size = New System.Drawing.Size(137, 24)
Me.DropLocationLabel.Text = "None"
' Form1
Me.ClientSize = New System.Drawing.Size(292, 270)
Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.ListDragSource, _
Me.ListDragTarget, Me.UseCustomCursorsCheck, _
Me.DropLocationLabel})
Me.Text = "drag-and-drop Example"
Me.ResumeLayout(False)
End Sub
Private Sub ListDragSource_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ListDragSource.MouseDown
' Get the index of the item the mouse is below.
indexOfItemUnderMouseToDrag = ListDragSource.IndexFromPoint(e.X, e.Y)
If (indexOfItemUnderMouseToDrag <> ListBox.NoMatches) Then
' 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.
Dim dragSize As Size = 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
End If
End Sub
Private Sub ListDragSource_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ListDragSource.MouseUp
' Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle.Empty
End Sub
Private Sub ListDragSource_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ListDragSource.MouseMove
If ((e.Button And MouseButtons.Left) = MouseButtons.Left) Then
' If the mouse moves outside the rectangle, start the drag.
If (Rectangle.op_Inequality(dragBoxFromMouseDown, Rectangle.Empty) And _
Not dragBoxFromMouseDown.Contains(e.X, e.Y)) Then
' Creates 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.
Dim dropEffect As DragDropEffects = ListDragSource.DoDragDrop(ListDragSource.Items(indexOfItemUnderMouseToDrag), _
DragDropEffects.All Or DragDropEffects.Link)
' If the drag operation was a move then remove the item.
If (dropEffect = DragDropEffects.Move) Then
ListDragSource.Items.RemoveAt(indexOfItemUnderMouseToDrag)
' Select the previous item in the list as long as the list has an item.
If (indexOfItemUnderMouseToDrag > 0) Then
ListDragSource.SelectedIndex = indexOfItemUnderMouseToDrag - 1
ElseIf (ListDragSource.Items.Count > 0) Then
' Selects the first item.
ListDragSource.SelectedIndex = 0
End If
End If
' Dispose the cursors since they are no longer needed.
If (Not MyNormalCursor Is Nothing) Then _
MyNormalCursor.Dispose()
If (Not MyNoDropCursor Is Nothing) Then _
MyNoDropCursor.Dispose()
End Try
End If
End If
End Sub
Private Sub ListDragSource_GiveFeedback(ByVal sender As Object, ByVal e As GiveFeedbackEventArgs) Handles ListDragSource.GiveFeedback
' Use custom cursors if the check box is checked.
If (UseCustomCursorsCheck.Checked) Then
' Set the custom cursor based upon the effect.
e.UseDefaultCursors = False
If ((e.Effect And DragDropEffects.Move) = DragDropEffects.Move) Then
Cursor.Current = MyNormalCursor
Else
Cursor.Current = MyNoDropCursor
End If
End If
End Sub
Private Sub ListDragTarget_DragOver(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragOver
' Determine whether string data exists in the drop data. If not, then
' the drop effect reflects that the drop cannot occur.
If Not (e.Data.GetDataPresent(GetType(System.String))) Then
e.Effect = DragDropEffects.None
DropLocationLabel.Text = "None - no string data."
Return
End If
' Set the effect based upon the KeyState.
If ((e.KeyState And (8 + 32)) = (8 + 32) And _
(e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then
' KeyState 8 + 32 = CTL + ALT
' Link drag-and-drop effect.
e.Effect = DragDropEffects.Link
ElseIf ((e.KeyState And 32) = 32 And _
(e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then
' ALT KeyState for link.
e.Effect = DragDropEffects.Link
ElseIf ((e.KeyState And 4) = 4 And _
(e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then
' SHIFT KeyState for move.
e.Effect = DragDropEffects.Move
ElseIf ((e.KeyState And 8) = 8 And _
(e.AllowedEffect And DragDropEffects.Copy) = DragDropEffects.Copy) Then
' CTL KeyState for copy.
e.Effect = DragDropEffects.Copy
ElseIf ((e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then
' By default, the drop action should be move, if allowed.
e.Effect = DragDropEffects.Move
Else
e.Effect = DragDropEffects.None
End If
' Gets 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) Then
DropLocationLabel.Text = "Drops before item #" & (indexOfItemUnderMouseToDrop + 1)
Else
DropLocationLabel.Text = "Drops at the end."
End If
End Sub
Private Sub ListDragTarget_DragDrop(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragDrop
' Ensures that the list item index is contained in the data.
If (e.Data.GetDataPresent(GetType(System.String))) Then
Dim item As Object = CType(e.Data.GetData(GetType(System.String)), System.Object)
' Perform drag-and-drop, depending upon the effect.
If (e.Effect = DragDropEffects.Copy Or _
e.Effect = DragDropEffects.Move) Then
' Insert the item.
If (indexOfItemUnderMouseToDrop <> ListBox.NoMatches) Then
ListDragTarget.Items.Insert(indexOfItemUnderMouseToDrop, item)
Else
ListDragTarget.Items.Add(item)
End If
End If
' Reset the label text.
DropLocationLabel.Text = "None"
End If
End Sub
Private Sub ListDragSource_QueryContinueDrag(ByVal sender As Object, ByVal e As QueryContinueDragEventArgs) Handles ListDragSource.QueryContinueDrag
' Cancel the drag if the mouse moves off the form.
Dim lb as ListBox = CType(sender, System.Windows.Forms.ListBox)
If Not (lb is nothing) Then
Dim f as Form = 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) Or _
((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) Or _
((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) Or _
((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) Then
e.Action = DragAction.Cancel
End If
End if
End Sub
Private Sub ListDragTarget_DragEnter(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragEnter
' Reset the label text.
DropLocationLabel.Text = "None"
End Sub
Private Sub ListDragTarget_DragLeave(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListDragTarget.DragLeave
' Reset the label text.
DropLocationLabel.Text = "None"
End Sub
End Class
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";
}
}
}
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
namespace Snip_DragNDrop
{
public ref class Form1: public System::Windows::Forms::Form
{
private:
System::Windows::Forms::ListBox^ ListDragSource;
System::Windows::Forms::ListBox^ ListDragTarget;
System::Windows::Forms::CheckBox^ UseCustomCursorsCheck;
System::Windows::Forms::Label ^ DropLocationLabel;
Int32 indexOfItemUnderMouseToDrag;
Int32 indexOfItemUnderMouseToDrop;
Rectangle dragBoxFromMouseDown;
Point screenOffset;
System::Windows::Forms::Cursor^ MyNoDropCursor;
System::Windows::Forms::Cursor^ MyNormalCursor;
public:
Form1()
{
this->ListDragSource = gcnew System::Windows::Forms::ListBox;
this->ListDragTarget = gcnew System::Windows::Forms::ListBox;
this->UseCustomCursorsCheck = gcnew System::Windows::Forms::CheckBox;
this->DropLocationLabel = gcnew System::Windows::Forms::Label;
this->SuspendLayout();
// ListDragSource
array<Object^>^temp0 = {"five","six","seven","eight","nine","ten"};
this->ListDragSource->Items->AddRange( temp0 );
this->ListDragSource->Location = System::Drawing::Point( 10, 17 );
this->ListDragSource->Size = System::Drawing::Size( 120, 225 );
this->ListDragSource->MouseDown += gcnew System::Windows::Forms::MouseEventHandler( this, &Form1::ListDragSource_MouseDown );
this->ListDragSource->QueryContinueDrag += gcnew System::Windows::Forms::QueryContinueDragEventHandler( this, &Form1::ListDragSource_QueryContinueDrag );
this->ListDragSource->MouseUp += gcnew System::Windows::Forms::MouseEventHandler( this, &Form1::ListDragSource_MouseUp );
this->ListDragSource->MouseMove += gcnew System::Windows::Forms::MouseEventHandler( this, &Form1::ListDragSource_MouseMove );
this->ListDragSource->GiveFeedback += gcnew System::Windows::Forms::GiveFeedbackEventHandler( this, &Form1::ListDragSource_GiveFeedback );
// ListDragTarget
this->ListDragTarget->AllowDrop = true;
this->ListDragTarget->Location = System::Drawing::Point( 154, 17 );
this->ListDragTarget->Size = System::Drawing::Size( 120, 225 );
this->ListDragTarget->DragOver += gcnew System::Windows::Forms::DragEventHandler( this, &Form1::ListDragTarget_DragOver );
this->ListDragTarget->DragDrop += gcnew System::Windows::Forms::DragEventHandler( this, &Form1::ListDragTarget_DragDrop );
this->ListDragTarget->DragEnter += gcnew System::Windows::Forms::DragEventHandler( this, &Form1::ListDragTarget_DragEnter );
this->ListDragTarget->DragLeave += gcnew System::EventHandler( this, &Form1::ListDragTarget_DragLeave );
// UseCustomCursorsCheck
this->UseCustomCursorsCheck->Location = System::Drawing::Point( 10, 243 );
this->UseCustomCursorsCheck->Size = System::Drawing::Size( 137, 24 );
this->UseCustomCursorsCheck->Text = "Use Custom Cursors";
// DropLocationLabel
this->DropLocationLabel->Location = System::Drawing::Point( 154, 245 );
this->DropLocationLabel->Size = System::Drawing::Size( 137, 24 );
this->DropLocationLabel->Text = "None";
// Form1
this->ClientSize = System::Drawing::Size( 292, 270 );
array<System::Windows::Forms::Control^>^formControls = {this->ListDragSource,this->ListDragTarget,this->UseCustomCursorsCheck,this->DropLocationLabel};
this->Controls->AddRange( formControls );
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 = this->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.
System::Drawing::Size dragSize = SystemInformation::DragSize;
// Create a rectangle using the DragSize, with the mouse position being
// at the center of the rectangle.
dragBoxFromMouseDown = Rectangle(Point(e->X - (dragSize.Width / 2),e->Y - (dragSize.Height / 2)),dragSize);
}
else
dragBoxFromMouseDown = Rectangle::Empty;
// Reset the rectangle if the mouse is not over an item in the ListBox.
}
void ListDragSource_MouseUp( Object^ /*sender*/, System::Windows::Forms::MouseEventArgs^ /*e*/ )
{
// Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle::Empty;
}
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 = gcnew System::Windows::Forms::Cursor( "3dwarro.cur" );
MyNoDropCursor = gcnew System::Windows::Forms::Cursor( "3dwno.cur" );
}
catch ( Exception^ )
{
// An error occurred while attempting to load the cursors, so use
// the standard cursors.
this->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 = this->ListDragSource->DoDragDrop( ListDragSource->Items[ indexOfItemUnderMouseToDrag ], static_cast<DragDropEffects>(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 != nullptr )
delete MyNormalCursor;
if ( MyNoDropCursor != nullptr )
delete MyNoDropCursor;
}
}
}
}
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;
}
}
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( System::String::typeid ) )
{
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( Point(e->X,e->Y) ) );
// Updates the label text.
if ( indexOfItemUnderMouseToDrop != ListBox::NoMatches )
{
DropLocationLabel->Text = String::Concat( "Drops before item # ", (indexOfItemUnderMouseToDrop + 1) );
}
else
DropLocationLabel->Text = "Drops at the end.";
}
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( System::String::typeid ) )
{
Object^ item = dynamic_cast<Object^>(e->Data->GetData( System::String::typeid ));
// 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";
}
void ListDragSource_QueryContinueDrag( Object^ sender, System::Windows::Forms::QueryContinueDragEventArgs^ e )
{
// Cancel the drag if the mouse moves off the form.
ListBox^ lb = dynamic_cast<ListBox^>(sender);
if ( lb != nullptr )
{
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;
}
}
}
void ListDragTarget_DragEnter( Object^ /*sender*/, System::Windows::Forms::DragEventArgs^ /*e*/ )
{
// Reset the label text.
DropLocationLabel->Text = "None";
}
void ListDragTarget_DragLeave( Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
// Reset the label text.
DropLocationLabel->Text = "None";
}
};
}
/// The main entry point for the application.
[STAThread]
int main()
{
Application::Run( gcnew Snip_DragNDrop::Form1 );
}
package SnipDragNDrop;
import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;
public class Form1 extends 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.
/** @attribute STAThread()
*/
public static void main(String[] args)
{
Application.Run(new Form1());
} //main
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.get_Items().AddRange(new Object[] { "one", "two",
"three", "four", "five", "six", "seven", "eight", "nine", "ten" });
this.listDragSource.set_Location(new System.Drawing.Point(10, 17));
this.listDragSource.set_Size(new System.Drawing.Size(120, 225));
this.listDragSource.add_MouseDown(
new System.Windows.Forms.MouseEventHandler(
this.listDragSource_MouseDown));
this.listDragSource.add_QueryContinueDrag(
new System.Windows.Forms.QueryContinueDragEventHandler(
this.listDragSource_QueryContinueDrag));
this.listDragSource.add_MouseUp(
new System.Windows.Forms.MouseEventHandler(
this.listDragSource_MouseUp));
this.listDragSource.add_MouseMove(
new System.Windows.Forms.MouseEventHandler(
this.listDragSource_MouseMove));
this.listDragSource.add_GiveFeedback(
new System.Windows.Forms.GiveFeedbackEventHandler(
this.listDragSource_GiveFeedback));
// listDragTarget
this.listDragTarget.set_AllowDrop(true);
this.listDragTarget.set_Location(new System.Drawing.Point(154, 17));
this.listDragTarget.set_Size(new System.Drawing.Size(120, 225));
this.listDragTarget.add_DragOver(
new System.Windows.Forms.DragEventHandler(
this.listDragTarget_DragOver));
this.listDragTarget.add_DragDrop(
new System.Windows.Forms.DragEventHandler(
this.listDragTarget_DragDrop));
this.listDragTarget.add_DragEnter(
new System.Windows.Forms.DragEventHandler(
this.listDragTarget_DragEnter));
this.listDragTarget.add_DragLeave(
new System.EventHandler(this.listDragTarget_DragLeave));
// useCustomCursorsCheck
this.useCustomCursorsCheck.set_Location(
new System.Drawing.Point(10, 243));
this.useCustomCursorsCheck.set_Size(new System.Drawing.Size(137, 24));
this.useCustomCursorsCheck.set_Text("Use Custom Cursors");
// dropLocationLabel
this.dropLocationLabel.set_Location(
new System.Drawing.Point(154, 245));
this.dropLocationLabel.set_Size(new System.Drawing.Size(137, 24));
this.dropLocationLabel.set_Text("None");
// Form1
this.set_ClientSize(new System.Drawing.Size(292, 270));
this.get_Controls().AddRange(new System.Windows.Forms.Control[] {
this.listDragSource, this.listDragTarget,
this.useCustomCursorsCheck, this.dropLocationLabel });
this.set_Text("drag-and-drop Example");
this.ResumeLayout(false);
} //Form1
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.get_X(),
e.get_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.get_DragSize();
// Create a rectangle using the DragSize, with the mouse position
// being at the center of the rectangle.
dragBoxFromMouseDown = new Rectangle(new Point(e.get_X()
- dragSize.get_Width() / 2, e.get_Y()
- dragSize.get_Height() / 2), dragSize);
}
// Reset the rectangle if the mouse is not over an item in the ListBox.
else {
dragBoxFromMouseDown = Rectangle.Empty;
}
} //listDragSource_MouseDown
private void listDragSource_MouseUp(Object sender,
System.Windows.Forms.MouseEventArgs e)
{
// Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle.Empty;
} //listDragSource_MouseUp
private void listDragSource_MouseMove(Object sender,
System.Windows.Forms.MouseEventArgs e)
{
if ((e.get_Button() & get_MouseButtons().Left)
== get_MouseButtons().Left) {
// If the mouse moves outside the rectangle, start the drag.
if (!(dragBoxFromMouseDown.Equals(Rectangle.Empty))
&& !(dragBoxFromMouseDown.Contains(e.get_X(), e.get_Y()))) {
// Create custom cursors for the drag-and-drop operation.
try {
myNormalCursor = new Cursor("3dwarro.cur");
myNoDropCursor = new Cursor("3dwno.cur");
}
catch (System.Exception exp) {
// An error occurred while attempting to load the cursors,
// so use standard cursors.
useCustomCursorsCheck.set_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.get_WorkingArea().get_Location();
// Proceed with the drag-and-drop, passing in the list item.
DragDropEffects dropEffect = listDragSource.DoDragDrop(
listDragSource.get_Items().get_Item(
indexOfItemUnderMouseToDrag),
DragDropEffects.All | DragDropEffects.Link);
// If the drag operation was a move then remove the item.
if (dropEffect.Equals(DragDropEffects.Move)) {
listDragSource.get_Items().RemoveAt(
indexOfItemUnderMouseToDrag);
// Selects the previous item in the list as long as the
// list has an item.
if (indexOfItemUnderMouseToDrag > 0) {
listDragSource.set_SelectedIndex(
indexOfItemUnderMouseToDrag - 1);
}
else {
if (listDragSource.get_Items().get_Count() > 0) {
// Selects the first item.
listDragSource.set_SelectedIndex(0);
}
}
}
// Dispose of the cursors since they are no longer needed.
if (myNormalCursor != null) {
myNormalCursor.Dispose();
}
if (myNoDropCursor != null) {
myNoDropCursor.Dispose();
}
}
}
}
} //listDragSource_MouseMove
private void listDragSource_GiveFeedback(Object sender,
System.Windows.Forms.GiveFeedbackEventArgs e)
{
// Use custom cursors if the check box is checked.
if (useCustomCursorsCheck.get_Checked()) {
// Sets the custom cursor based upon the effect.
e.set_UseDefaultCursors(false);
if ((e.get_Effect() & DragDropEffects.Move)
== DragDropEffects.Move) {
get_Cursor().set_Current(myNormalCursor);
}
else {
get_Cursor().set_Current(myNoDropCursor);
}
}
} //listDragSource_GiveFeedback
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.get_Data().GetDataPresent(String.class.ToType()))) {
e.set_Effect(DragDropEffects.None);
dropLocationLabel.set_Text("None - no string data.");
return;
}
// Set the effect based upon the KeyState.
if ((e.get_KeyState() & 8 + 32) == 8 + 32 && (e.get_AllowedEffect()
& DragDropEffects.Link) == DragDropEffects.Link) {
// KeyState 8 + 32 = CTL + ALT
// Link drag-and-drop effect.
e.set_Effect(DragDropEffects.Link);
}
else {
if ((e.get_KeyState() & 32) == 32 && (e.get_AllowedEffect()
& DragDropEffects.Link) == DragDropEffects.Link) {
// ALT KeyState for link.
e.set_Effect(DragDropEffects.Link);
}
else {
if ((e.get_KeyState() & 4) == 4 && (e.get_AllowedEffect()
& DragDropEffects.Move) == DragDropEffects.Move) {
// SHIFT KeyState for move.
e.set_Effect(DragDropEffects.Move);
}
else {
if ((e.get_KeyState() & 8) == 8 && (e.get_AllowedEffect()
& DragDropEffects.Copy) == DragDropEffects.Copy) {
// CTL KeyState for copy.
e.set_Effect(DragDropEffects.Copy);
}
else {
if ((e.get_AllowedEffect() & DragDropEffects.Move)
== DragDropEffects.Move) {
// By default, the drop action should be move,
//if allowed.
e.set_Effect(DragDropEffects.Move);
}
else {
e.set_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.get_X(), e.get_Y())));
// Updates the label text.
if (indexOfItemUnderMouseToDrop != ListBox.NoMatches) {
dropLocationLabel.set_Text("Drops before item #"
+ (indexOfItemUnderMouseToDrop + 1));
}
else {
dropLocationLabel.set_Text("Drops at the end.");
}
} //listDragTarget_DragOver
private void listDragTarget_DragDrop(Object sender,
System.Windows.Forms.DragEventArgs e)
{
// Ensure that the list item index is contained in the data.
if (e.get_Data().GetDataPresent(String.class.ToType())) {
Object item = (Object)(e.get_Data().GetData(
String.class.ToType()));
// Perform drag-and-drop, depending upon the effect.
if (e.get_Effect().Equals(DragDropEffects.Copy) ||
e.get_Effect().Equals(DragDropEffects.Move)) {
// Insert the item.
if (indexOfItemUnderMouseToDrop != ListBox.NoMatches) {
listDragTarget.get_Items().Insert(
indexOfItemUnderMouseToDrop, item);
}
else {
listDragTarget.get_Items().Add(item);
}
}
}
// Reset the label text.
dropLocationLabel.set_Text("None");
} //listDragTarget_DragDrop
private void listDragSource_QueryContinueDrag(Object sender,
System.Windows.Forms.QueryContinueDragEventArgs e)
{
// Cancel the drag if the mouse moves off the form.
ListBox lb = (ListBox)sender;
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.get_MousePosition().get_X() - screenOffset.get_X()
< f.get_DesktopBounds().get_Left()
|| Control.get_MousePosition().get_X()
- screenOffset.get_X() > f.get_DesktopBounds().get_Right()
|| Control.get_MousePosition().get_Y() - screenOffset.get_Y()
< f.get_DesktopBounds().get_Top()
|| Control.get_MousePosition().get_Y() - screenOffset.get_Y()
> f.get_DesktopBounds().get_Bottom()) {
e.set_Action(DragAction.Cancel);
}
}
} //listDragSource_QueryContinueDrag
private void listDragTarget_DragEnter(Object sender,
System.Windows.Forms.DragEventArgs e)
{
// Reset the label text.
dropLocationLabel.set_Text("None");
} //listDragTarget_DragEnter
private void listDragTarget_DragLeave(Object sender, System.EventArgs e)
{
// Reset the label text.
dropLocationLabel.set_Text("None");
} //listDragTarget_DragLeave
} //Form1
下面的代码示例演示如何使用 DragDropEffects 枚举指定数据应如何在拖放操作中涉及到的控件之间进行传送。此示例要求您的窗体中包括一个 RichTextBox 控件和一个 Label 控件，并且 Label 控件用有效文件名列表进行填充。当用户将文件名拖到 RichTextBox 控件上时，该控件的 DragEnter 事件被引发。在事件处理程序中，DragEventArgs 的 Effect 属性被初始化为 DragDropEffects，以便指示该文件路径所引用的数据应复制到 RichTextBox 控件中。
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
' Sets the AllowDrop property so that data can be dragged onto the control.
RichTextBox1.AllowDrop = True
' Add code here to populate the ListBox1 with paths to text files.
End Sub
Private Sub RichTextBox1_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles RichTextBox1.DragEnter
' If the data is text, copy the data to the RichTextBox control.
If (e.Data.GetDataPresent("Text")) Then
e.Effect = DragDropEffects.Copy
End If
End Sub
Private Overloads Sub RichTextBox1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles RichTextBox1.DragDrop
' Loads the file into the control.
RichTextBox1.LoadFile(e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText)
End Sub
Private Sub ListBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListBox1.MouseDown
Dim Lb As ListBox
Dim Pt As New Point(e.X, e.Y)
Dim Index As Integer
' Determines which item was selected.
Lb = sender
Index = Lb.IndexFromPoint(Pt)
' Starts a drag-and-drop operation with that item.
If Index >= 0 Then
Lb.DoDragDrop(Lb.Items(Index), DragDropEffects.Link)
End If
End Sub
private void Form1_Load(object sender, EventArgs e)
{
// Sets the AllowDrop property so that data can be dragged onto the control.
richTextBox1.AllowDrop = true;
// Add code here to populate the ListBox1 with paths to text files.
}
private void listBox1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
// Determines which item was selected.
ListBox lb =( (ListBox)sender);
Point pt = new Point(e.X,e.Y);
int index = lb.IndexFromPoint(pt);
// Starts a drag-and-drop operation with that item.
if(index>=0)
{
lb.DoDragDrop(lb.Items[index].ToString(), DragDropEffects.Link);
}
}
private void richTextBox1_DragEnter(object sender, DragEventArgs e)
{
// If the data is text, copy the data to the RichTextBox control.
if(e.Data.GetDataPresent("Text"))
e.Effect = DragDropEffects.Copy;
}
private void richTextBox1_DragDrop(object sender, DragEventArgs e)
{
// Loads the file into the control.
richTextBox1.LoadFile((String)e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText);
}
private:
void Form1_Load( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// Sets the AllowDrop property so that data can be dragged onto the control.
richTextBox1->AllowDrop = true;
// Add code here to populate the ListBox1 with paths to text files.
}
void listBox1_MouseDown( Object^ sender, System::Windows::Forms::MouseEventArgs^ e )
{
// Determines which item was selected.
ListBox^ lb = (dynamic_cast<ListBox^>(sender));
Point pt = Point(e->X,e->Y);
int index = lb->IndexFromPoint( pt );
// Starts a drag-and-drop operation with that item.
if ( index >= 0 )
{
lb->DoDragDrop( lb->Items[ index ], DragDropEffects::Link );
}
}
void richTextBox1_DragEnter( Object^ /*sender*/, DragEventArgs^ e )
{
// If the data is text, copy the data to the RichTextBox control.
if ( e->Data->GetDataPresent( "Text" ) )
e->Effect = DragDropEffects::Copy;
}
void richTextBox1_DragDrop( Object^ /*sender*/, DragEventArgs^ e )
{
// Loads the file into the control.
richTextBox1->LoadFile( dynamic_cast<String^>(e->Data->GetData( "Text" )), System::Windows::Forms::RichTextBoxStreamType::RichText );
}
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
请参见
参考
Control 类
Control 成员
System.Windows.Forms 命名空间
AllowDrop
DragDrop