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Microsoft Visual Studio 2005/.NET Framework 2.0

Hay además otras versiones disponibles para:
Control.AllowDrop (Propiedad)
Obtiene o establece un valor que indica si el control puede aceptar los datos que el usuario arrastra al mismo.

Espacio de nombres: System.Windows.Forms
Ensamblado: System.Windows.Forms (en system.windows.forms.dll)

Visual Basic (Declaración)
Public Overridable Property AllowDrop As Boolean
Visual Basic (Uso)
Dim instance As Control
Dim value As Boolean

value = instance.AllowDrop

instance.AllowDrop = value
C#
public virtual bool AllowDrop { get; set; }
C++
public:
virtual property bool AllowDrop {
    bool get ();
    void set (bool value);
}
J#
/** @property */
public boolean get_AllowDrop ()

/** @property */
public void set_AllowDrop (boolean value)
JScript
public function get AllowDrop () : boolean

public function set AllowDrop (value : boolean)
XAML
No aplicable.

Valor de propiedad

Es true si se permite realizar operaciones de arrastrar y colocar en el control; en caso contrario, es false. El valor predeterminado es false.

Notas para los herederos: Cuando se reemplaza la propiedad AllowDrop en una clase derivada, hay que utilizar la propiedad AllowDrop de la clase base para extender la implementación base. Si no, deberá proporcionarse toda la implementación. No es necesario reemplazar ambos descriptores de acceso get y set de la propiedad AllowDrop; se puede reemplazar sólo uno, si es necesario.

En el ejemplo siguiente de código se muestra cómo permitir al usuario arrastrar una imagen o un archivo de imagen al formulario, y mostrarlo en el lugar donde se coloque. El método OnPaint se reemplaza para volver a dibujar la imagen cada vez que se dibuje el formulario; en caso contrario, la imagen sólo se conserva hasta la siguiente operación de dibujo. El método de control de eventos DragEnter determina el tipo de datos que se arrastra al formulario y proporciona la información apropiada. El método de control de eventos DragDrop muestra la imagen en el formulario si se puede crear Image a partir de los datos. Como los valores de las propiedades DragEventArgs.X y DragEventArgs.Y son coordenadas de pantalla, se utiliza en el ejemplo el método PointToClient para convertirlas a coordenadas de cliente.

Visual Basic
Private picture As Image
Private pictureLocation As Point

Public Sub New()
   ' Enable drag-and-drop operations.
   Me.AllowDrop = True
End Sub

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
   MyBase.OnPaint(e)

   ' If there is an image and it has a location, 
   ' paint it when the Form is repainted.
   If (Me.picture IsNot Nothing) And _
     Not (Me.pictureLocation.Equals(Point.Empty)) Then
      e.Graphics.DrawImage(Me.picture, Me.pictureLocation)
   End If
End Sub

Private Sub Form1_DragDrop(ByVal sender As Object, _
  ByVal e As DragEventArgs) Handles MyBase.DragDrop
   ' Handle FileDrop data.
   If e.Data.GetDataPresent(DataFormats.FileDrop) Then
      ' Assign the file names to a string array, in 
      ' case the user has selected multiple files.
      Dim files As String() = CType(e.Data.GetData(DataFormats.FileDrop), String())
      Try
         ' Assign the first image to the 'picture' variable.
         Me.picture = Image.FromFile(files(0))
         ' Set the picture location equal to the drop point.
         Me.pictureLocation = Me.PointToClient(New Point(e.X, e.Y))
      Catch ex As Exception
         MessageBox.Show(ex.Message)
         Return
      End Try
   End If

   ' Handle Bitmap data.
   If e.Data.GetDataPresent(DataFormats.Bitmap) Then
      Try
         ' Create an Image and assign it to the picture variable.
         Me.picture = CType(e.Data.GetData(DataFormats.Bitmap), Image)
         ' Set the picture location equal to the drop point.
         Me.pictureLocation = Me.PointToClient(New Point(e.X, e.Y))
      Catch ex As Exception
         MessageBox.Show(ex.Message)
         Return
      End Try
   End If

   ' Force the form to be redrawn with the image.
   Me.Invalidate()
End Sub

Private Sub Form1_DragEnter(ByVal sender As Object, _
  ByVal e As DragEventArgs) Handles MyBase.DragEnter
   ' If the data is a file or a bitmap, display the copy cursor.
   If e.Data.GetDataPresent(DataFormats.Bitmap) _
      Or e.Data.GetDataPresent(DataFormats.FileDrop) Then
      e.Effect = DragDropEffects.Copy
   Else
      e.Effect = DragDropEffects.None
   End If
End Sub
C#
private Image picture;
private Point pictureLocation;

public Form1()
{
   // Enable drag-and-drop operations and 
   // add handlers for DragEnter and DragDrop.
   this.AllowDrop = true;
   this.DragDrop += new DragEventHandler(this.Form1_DragDrop);
   this.DragEnter += new DragEventHandler(this.Form1_DragEnter);
}

protected override void OnPaint(PaintEventArgs e)
{
   // If there is an image and it has a location, 
   // paint it when the Form is repainted.
   base.OnPaint(e);
   if(this.picture != null && this.pictureLocation != Point.Empty)
   {
      e.Graphics.DrawImage(this.picture, this.pictureLocation);
   }
}

private void Form1_DragDrop(object sender, DragEventArgs e)
{
   // Handle FileDrop data.
   if(e.Data.GetDataPresent(DataFormats.FileDrop) )
   {
      // Assign the file names to a string array, in 
      // case the user has selected multiple files.
      string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
      try
      {
         // Assign the first image to the picture variable.
         this.picture = Image.FromFile(files[0]);
         // Set the picture location equal to the drop point.
         this.pictureLocation = this.PointToClient(new Point(e.X, e.Y) );
      }
      catch(Exception ex)
      {
         MessageBox.Show(ex.Message);
         return;
      }
   }

   // Handle Bitmap data.
   if(e.Data.GetDataPresent(DataFormats.Bitmap) )
   {
      try
      {
         // Create an Image and assign it to the picture variable.
         this.picture = (Image)e.Data.GetData(DataFormats.Bitmap);
         // Set the picture location equal to the drop point.
         this.pictureLocation = this.PointToClient(new Point(e.X, e.Y) );
      }
      catch(Exception ex)
      {
         MessageBox.Show(ex.Message);
         return;
      }
   }
   // Force the form to be redrawn with the image.
   this.Invalidate();
}

private void Form1_DragEnter(object sender, DragEventArgs e)
{
   // If the data is a file or a bitmap, display the copy cursor.
   if (e.Data.GetDataPresent(DataFormats.Bitmap) || 
      e.Data.GetDataPresent(DataFormats.FileDrop) ) 
   {
      e.Effect = DragDropEffects.Copy;
   }
   else
   {
      e.Effect = DragDropEffects.None;
   }
}
C++
private:
   Image^ picture;
   Point pictureLocation;

public:
   Form1()
   {
      
      // Enable drag-and-drop operations and
      // add handlers for DragEnter and DragDrop.
      this->AllowDrop = true;
      this->DragDrop += gcnew DragEventHandler( this, &Form1::Form1_DragDrop );
      this->DragEnter += gcnew DragEventHandler( this, &Form1::Form1_DragEnter );
   }

protected:
   virtual void OnPaint( PaintEventArgs^ e ) override
   {
      
      // If there is an image and it has a location,
      // paint it when the Form is repainted.
      Form::OnPaint( e );
      if ( this->picture != nullptr && this->pictureLocation != Point::Empty )
      {
         e->Graphics->DrawImage( this->picture, this->pictureLocation );
      }
   }

private:
   void Form1_DragDrop( Object^ /*sender*/, DragEventArgs^ e )
   {
      
      // Handle FileDrop data.
      if ( e->Data->GetDataPresent( DataFormats::FileDrop ) )
      {
         // Assign the file names to a String* array, in
         // case the user has selected multiple files.
         array<String^>^files = (array<String^>^)e->Data->GetData( DataFormats::FileDrop );
         try
         {
            // Assign the first image to the picture variable.
            this->picture = Image::FromFile( files[ 0 ] );
            
            // Set the picture location equal to the drop point.
            this->pictureLocation = this->PointToClient( Point(e->X,e->Y) );
         }
         catch ( Exception^ ex ) 
         {
            MessageBox::Show( ex->Message );
            return;
         }

      }
      
      // Handle Bitmap data.
      if ( e->Data->GetDataPresent( DataFormats::Bitmap ) )
      {
         try
         {
            // Create an Image and assign it to the picture variable.
            this->picture = dynamic_cast<Image^>(e->Data->GetData( DataFormats::Bitmap ));

            // Set the picture location equal to the drop point.
            this->pictureLocation = this->PointToClient( Point(e->X,e->Y) );
         }
         catch ( Exception^ ex ) 
         {
            MessageBox::Show( ex->Message );
            return;
         }
      }
      
      // Force the form to be redrawn with the image.
      this->Invalidate();
   }

   void Form1_DragEnter( Object^ /*sender*/, DragEventArgs^ e )
   {
      // If the data is a file or a bitmap, display the copy cursor.
      if ( e->Data->GetDataPresent( DataFormats::Bitmap ) || e->Data->GetDataPresent( DataFormats::FileDrop ) )
      {
         e->Effect = DragDropEffects::Copy;
      }
      else
      {
         e->Effect = DragDropEffects::None;
      }
   }
J#
private Image picture;
private Point pictureLocation;

public Form1()
{
    // Enable drag-and-drop operations and 
    // add handlers for DragEnter and DragDrop.
    this.set_AllowDrop(true);
    this.add_DragDrop(new DragEventHandler(this.Form1_DragDrop));
    this.add_DragEnter(new DragEventHandler(this.Form1_DragEnter));
} //Form1

protected void OnPaint(PaintEventArgs e)
{
    // If there is an image and it has a location, 
    // paint it when the Form is repainted.
    super.OnPaint(e);
    if (this.picture != null && !this.pictureLocation.Equals(Point.Empty)) {
        e.get_Graphics().DrawImage(this.picture, this.pictureLocation);
    }
} //OnPaint

private void Form1_DragDrop(Object sender, DragEventArgs e)
{
    // Handle FileDrop data.
    if (e.get_Data().GetDataPresent(DataFormats.FileDrop)) {
        // Assign the file names to a string array, in 
        // case the user has selected multiple files.
        String files[] = (String[])(e.get_Data().GetData(
            DataFormats.FileDrop));
        try {
            // Assign the first image to the picture variable.
            this.picture = Image.FromFile(files.toString());
            // Set the picture location equal to the drop point.
            this.pictureLocation = this.PointToClient(new Point(e.get_X(), 
                e.get_Y()));
        }
        catch (System.Exception ex) {
            MessageBox.Show(ex.get_Message());
            return;
        }
    }
    // Handle Bitmap data.
    if (e.get_Data().GetDataPresent(DataFormats.Bitmap)) {
        try {
            // Create an Image and assign it to the picture variable.
            this.picture = (Image)e.get_Data().GetData(DataFormats.Bitmap);
            // Set the picture location equal to the drop point.
            this.pictureLocation = this.PointToClient(new Point(e.get_X(), 
                e.get_Y()));
        }
        catch (System.Exception ex) {
            MessageBox.Show(ex.get_Message());
            return;
        }
    }
    // Force the form to be redrawn with the image.
    this.Invalidate();
} //Form1_DragDrop

private void Form1_DragEnter(Object sender, DragEventArgs e)
{
    // If the data is a file or a bitmap, display the copy cursor.
    if (e.get_Data().GetDataPresent(DataFormats.Bitmap) || e.get_Data().
        GetDataPresent(DataFormats.FileDrop)) {
        e.set_Effect(DragDropEffects.Copy);
    }
    else {
        e.set_Effect(DragDropEffects.None);
    }
} //Form1_DragEnter

Windows 98, Windows 2000 Service Pack 4, Windows CE, Windows Millennium, Windows Mobile para Pocket PC, Windows Mobile para Smartphone, Windows Server 2003, Windows XP Media Center, Windows XP Professional x64, Windows XP SP2, Windows XP Starter

Microsoft .NET Framework 3.0 es compatible con Windows Vista, Microsoft Windows XP SP2 y Windows Server 2003 SP1.

.NET Framework

Compatible con: 3.0, 2.0, 1.1, 1.0
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