Control.DoDragDrop(Object, DragDropEffects) Метод

Определение

Начинает операцию перетаскивания.

public:
 System::Windows::Forms::DragDropEffects DoDragDrop(System::Object ^ data, System::Windows::Forms::DragDropEffects allowedEffects);
public System.Windows.Forms.DragDropEffects DoDragDrop (object data, System.Windows.Forms.DragDropEffects allowedEffects);
member this.DoDragDrop : obj * System.Windows.Forms.DragDropEffects -> System.Windows.Forms.DragDropEffects
Public Function DoDragDrop (data As Object, allowedEffects As DragDropEffects) As DragDropEffects

Параметры

data
Object

Перетаскиваемые данные.

allowedEffects
DragDropEffects

Одно из значений перечисления DragDropEffects.

Возвращаемое значение

DragDropEffects

Значение перечисления DragDropEffects, представляющее конечный результат выполнения операции перетаскивания.

Примеры

В следующем примере кода демонстрируется операция перетаскивания между двумя ListBox элементами управления. В примере вызывается DoDragDrop метод при запуске действия перетаскивания. Действие перетаскивания начинается, если мышь переместилась больше, чем SystemInformation.DragSize из расположения мыши во время MouseDown события. Метод IndexFromPoint используется для определения индекса элемента для перетаскивания во время MouseDown события.

В этом примере также демонстрируется использование пользовательских курсоров для операции перетаскивания. В примере требуется, чтобы два файла курсора и 3dwarro.cur 3dwno.cur, существовали в каталоге приложения, для пользовательских курсоров перетаскивания и без перетаскивания соответственно. Пользовательские курсоры будут использоваться UseCustomCursorsCheck CheckBox при проверке. Пользовательские курсоры задаются в обработчике GiveFeedback событий.

Состояние клавиатуры вычисляется в DragOver обработчике событий справа ListBox, чтобы определить, какая операция перетаскивания будет зависеть от состояния клавиш SHIFT, CTRL, ALT или CTRL+ALT. Расположение в месте, где ListBox будет происходить удаление, также определяется во время DragOver события. Если удаляемые данные не Stringявляются, DragEventArgs.Effect то для нее задано значение None DragDropEffects. Наконец, в списке DropLocationLabel Labelотображается состояние удаления.

Данные, которые нужно удалить справаListBox, определяются в обработчике DragDrop событий, и String значение добавляется в соответствующее место в .ListBox Если операция перетаскивания перемещается за пределы формы, операция перетаскивания отменяется в обработчике QueryContinueDrag событий.

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 = CTRL + 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) )
         {
            // CTRL 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 );
}
using System;
using System.Drawing;
using System.Windows.Forms;

namespace Snip_DragNDrop
{
    public class Form1 : Form
    {
        private ListBox ListDragSource;
        private ListBox ListDragTarget;
        private CheckBox UseCustomCursorsCheck;
        private 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 ListBox();
            this.ListDragTarget = new ListBox();
            this.UseCustomCursorsCheck = new CheckBox();
            this.DropLocationLabel = new Label();

            this.SuspendLayout();

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

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

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

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

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

            this.ResumeLayout(false);
        }

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

        private void ListDragSource_MouseMove(object sender, 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, 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, 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 = CTRL + 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)
            {
                // CTRL 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, DragEventArgs e)
        {
            // Ensure that the list item index is contained in the data.
            if (e.Data.GetDataPresent(typeof(System.String)))
            {
                Object item = 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, 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, DragEventArgs e)
        {
            // Reset the label text.
            DropLocationLabel.Text = "None";
        }
        private void ListDragTarget_DragLeave(object sender, EventArgs e)
        {
            // Reset the label text.
            DropLocationLabel.Text = "None";
        }
    }
}
Imports System.Drawing
Imports System.Windows.Forms

Public NotInheritable Class Form1
    Inherits Form

    Friend WithEvents ListDragSource As ListBox
    Friend WithEvents ListDragTarget As ListBox
    Friend WithEvents UseCustomCursorsCheck As CheckBox
    Friend WithEvents DropLocationLabel As 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

    <STAThread()>
    Public Shared Sub Main()
        Application.Run(New Form1())
    End Sub

    Public Sub New()
        MyBase.New()

        Me.ListDragSource = New ListBox()
        Me.ListDragTarget = New ListBox()
        Me.UseCustomCursorsCheck = New CheckBox()
        Me.DropLocationLabel = New Label()

        Me.SuspendLayout()

        ' ListDragSource
        Me.ListDragSource.Items.AddRange(New Object() {"one", "two", "three", "four",
                                                       "five", "six", "seven", "eight",
                                                       "nine", "ten"})
        Me.ListDragSource.Location = New Point(10, 17)
        Me.ListDragSource.Size = New Size(120, 225)

        ' ListDragTarget
        Me.ListDragTarget.AllowDrop = True
        Me.ListDragTarget.Location = New Point(154, 17)
        Me.ListDragTarget.Size = New Size(120, 225)

        ' UseCustomCursorsCheck
        Me.UseCustomCursorsCheck.Location = New Point(10, 243)
        Me.UseCustomCursorsCheck.Size = New Size(137, 24)
        Me.UseCustomCursorsCheck.Text = "Use Custom Cursors"

        ' DropLocationLabel
        Me.DropLocationLabel.Location = New Point(154, 245)
        Me.DropLocationLabel.Size = New Size(137, 24)
        Me.DropLocationLabel.Text = "None"

        ' Form1
        Me.ClientSize = New Size(292, 270)
        Me.Controls.AddRange(New 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 = CTRL + 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

            ' CTRL 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, ListBox)

        If (lb IsNot 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 EventArgs) Handles ListDragTarget.DragLeave
        ' Reset the label text.
        DropLocationLabel.Text = "None"
    End Sub
End Class

В следующем примере кода показано, как использовать DragDropEffects перечисление для указания способа передачи данных между элементами управления, участвующими в операции перетаскивания. В этом примере требуется, чтобы форма содержит RichTextBox элемент управления и ListBox элемент управления, а ListBox элемент управления заполняется списком допустимых имен файлов. Когда пользователь перетаскивает имя файла в RichTextBox элемент управления, возникает событие элемента управления DragEnter . В обработчике событий свойство инициализируетсяDragEventArgs, чтобы DragDropEffects указать, что данные, Effect на которые ссылается путь к файлу, должны быть скопированы в RichTextBox элемент управления.

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 );
   }
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 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

Комментарии

Параметр allowedEffects определяет, какие операции перетаскивания могут выполняться. Если операция перетаскивания должна взаимодействовать с приложениями в другом процессе, данные должны быть либо базовым управляемым классом (Stringили), либо Metafileобъектом, реализующим ISerializable или IDataObjectBitmap.

Далее описывается, как и когда возникают события, связанные с операциями перетаскивания.

Метод DoDragDrop определяет элемент управления в текущем расположении курсора. Затем он проверяет, является ли элемент управления допустимым целевым объектом удаления.

Если элемент управления является допустимым целевым объектом перетаскивания, GiveFeedback событие вызывается с указанным эффектом перетаскивания. Список эффектов перетаскивания см. в перечислении DragDropEffects.

Отслеживаются изменения позиции указателя мыши, состояния клавиатуры и кнопки мыши.

  • Если пользователь перемещает указатель мыши за пределы окна, происходит событие DragLeave.

  • Если указатель мыши перемещается на другой элемент управления, для этого элемента вызывается событие DragEnter.

  • При перемещении мыши в пределах одного элемента управления возникает событие DragOver.

При изменении состояния QueryContinueDrag клавиатуры или кнопки мыши событие вызывается и определяет, следует ли продолжить перетаскивание, удалить данные или отменить операцию на основе значения Action свойства события QueryContinueDragEventArgs.

  • Если значение DragAction равно Continue, DragOver событие вызывается для продолжения операции, и GiveFeedback событие вызывается с новым эффектом, чтобы можно было задать соответствующую визуальную обратную связь. Список допустимых эффектов сброса см. в перечислении DragDropEffects.

    Примечание

    События DragOver GiveFeedback связаны таким образом, чтобы при перемещении мыши по целевому объекту перетаскивания пользователь получил самые актуальные отзывы о положении мыши.

  • Если значение DragAction равно Drop, значение эффекта перетаскивания возвращается источнику, чтобы исходное приложение смогла выполнить соответствующую операцию с исходными данными, например вырезать данные, если операция была перемещением.

  • Если значение DragAction равно Cancel, DragLeave вызывается событие.

Примечание

Метод DoDragDrop перехватывает все исключения и повторно выполняет только следующие исключения безопасности или критические исключения:

  • SecurityException

  • NullReferenceException

  • StackOverflowException

  • OutOfMemoryException

  • ThreadAbortException

  • ExecutionEngineException

  • IndexOutOfRangeException

  • AccessViolationException

Применяется к

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