Control.DoDragDrop メソッドとは何？わかりやすく解説 Weblio辞書

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.NET Framework クラスライブラリリファレンス

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Control.DoDragDrop メソッド

ドラッグアンドドロップ操作を開始します。

名前空間: System.Windows.Forms
アセンブリ: System.Windows.Forms (system.windows.forms.dll 内)
構文

Visual Basic (宣言)

Public Function DoDragDrop ( _
    data As Object, _
    allowedEffects As DragDropEffects _
) As DragDropEffects

Visual Basic (使用法)

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
)

C++

public:
DragDropEffects DoDragDrop (
    Object^ data, 
    DragDropEffects allowedEffects
)

public DragDropEffects DoDragDrop (
    Object data, 
    DragDropEffects allowedEffects
)

JScript

public function DoDragDrop (
    data : Object, 
    allowedEffects : DragDropEffects
) : DragDropEffects

パラメータ

data: ドラッグするデータ。

allowedEffects: DragDropEffects 値の 1 つ。

戻り値
ドラッグアンドドロップ操作中に実行された最終的な効果を表す、DragDropEffects 列挙体からの値。

解説

allowedEffects パラメータは、どのドラッグ操作が発生できるかを決定します。ドラッグ操作が別のプロセスのアプリケーションと相互運用する必要がある場合、データは、基本マネージクラス (String、Bitmap、または Metafile)、あるいは ISerializable または IDataObject を実装するオブジェクトのいずれかである必要があります。

DoDragDrop メソッドは、現在のカーソル位置に従ってコントロールを判別します。次に、コントロールが有効なドロップターゲットかどうかを確認します。

コントロールが有効なドロップターゲットの場合、指定したドラッグアンドドロップの効果が付いた状態で GiveFeedback イベントが発生します。ドラッグアンドドロップ効果の一覧については、DragDropEffects 列挙体を参照してください。

マウスカーソルの位置、キーボードの状態、およびマウスボタンの状態の変更が監視されます。

ユーザーがウィンドウの外に移動した場合、DragLeave イベントが生成されます。
マウスが別のコントロールに移動した場合は、そのコントロールの DragEnter が生成されます。
マウスが移動しても同じコントロール内の場合は、DragOver イベントが生成されます。

キーボードまたはマウスボタンの状態に変更があった場合、QueryContinueDrag イベントが生成され、このイベントの QueryContinueDragEventArgs の Action プロパティの値に応じて、ドラッグを継続するか、データをドロップするか、操作をキャンセルするかが判断されます。

DragAction の値が Continue の場合、操作を継続するための DragOver イベントが生成され、適切な視覚的フィードバックを設定できるように新しい効果による GiveFeedback イベントが生成されます。有効なドロップ効果の一覧については、DragDropEffects 列挙体を参照してください。

メモ
DragOver イベントおよび GiveFeedback イベントはペアになっています。したがって、マウスがドロップターゲットをまたがって移動した場合、マウスの位置に関する最新のフィードバックがユーザーに提示されます。

DragAction の値が Drop の場合、ドロップ効果の値がソースに返されます。ソースアプリケーションでは、ソースデータに対して適切な操作を実行できます。たとえば、移動操作だった場合は、データの切り取りなどを実行できます。
DragAction の値が Cancel の場合、DragLeave イベントが生成されます。

使用例

2 つの ListBox コントロールの間でドラッグアンドドロップ操作を実行するコード例を次に示します。この例では、ドラッグアクションが開始したときに DoDragDrop メソッドが呼び出されます。ドラッグ操作は、MouseDown イベント実行中のマウス位置から SystemInformation.DragSize を超えてマウスが移動したときに開始されます。IndexFromPoint メソッドは、MouseDown イベントで、ドラッグする項目のインデックスを判別するために使用します。

この例では、ドラッグアンドドロップ操作でカスタムカーソルを使用する方法についても示します。この例では、2 つのカーソルファイル (3dwarro.cur と 3dwno.cur) がアプリケーションディレクトリ内に存在している必要があります。なお、それぞれのファイルはドラッグ用のカスタムカーソルとドロップなしのカスタムカーソルを表します。カスタムカーソルは、UseCustomCursorsCheckCheckBox がオンになっている場合に使用されます。カスタムカーソルは、GiveFeedback イベントハンドラで設定されます。

キーボードの状態は、右側の ListBox の DragOver イベントハンドラで評価されます。ドラッグ操作の内容は、Shift キー、Ctrl キー、Alt キー、または Ctrl + Alt キーの状態によって決まります。ドロップが発生する ListBox 内の位置は、DragOver イベント時にも判定されます。ドロップするデータが String でない場合は、DragEventArgs.Effect が DragDropEffects で None に設定されます。最後に、ドロップのステータスが DropLocationLabelLabel に表示されます。

右側の ListBox にドロップするデータは、DragDrop イベントハンドラで判定されます。また、String 値が ListBox の該当する場所に追加されます。ドラッグ操作がフォームの範囲を超えて移動した場合、ドラッグアンドドロップ操作は QueryContinueDrag イベントハンドラでキャンセルされます。

Visual Basic

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";
        }
    }
}

C++

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

DragDropEffects 列挙体を使用して、ドラッグアンドドロップ操作に関与しているコントロール間でデータをどのように渡すかを指定する方法を、次のコード例に示します。この例では、RichTextBox コントロールおよび Label コントロールを含むフォームを使用しており、Label コントロールに有効なファイル名の一覧が設定されている必要があります。ユーザーが RichTextBox コントロールにファイル名をドラッグすると、このコントロールの DragEnter イベントが発生します。イベントハンドラ内では、DragEventArgs の Effect プロパティが DragDropEffects に初期化され、ファイルパスによって参照されているデータを RichTextBox コントロールにコピーすることを示します。

Visual Basic

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);
}

C++

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 );
   }

プラットフォーム

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

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0

参照

関連項目
Control クラス
Control メンバ
System.Windows.Forms 名前空間
AllowDrop
DragDrop

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