drag and drop between list boxes

drag and drop between list boxes

• clarkiwrc

  the zipped files for the drag drop operations in C# are located here:

  http://blogs.msdn.com/llobo/archive/2006/04/11/573560.aspx

  
  

• daat99

  Both VB.NET and C# Most Nifty. Thanks, Darius!
  

• thomasn

  freeflyr, I have a series of posts about drag-drop over at http://blogs.msdn.com/marcelolr/.

  The first post is http://blogs.msdn.com/marcelolr/archive/2006/03/02/542641.aspx, and the preview adorner gets introduced in http://blogs.msdn.com/marcelolr/archive/2006/03/03/543301.aspx.

  I'll post the complete code in a couple of posts - there are still a couple of things I'd like to touch upon to build the sample out a bit more.

  
  

• GMichaels

  In case anyone wants to just build the final result of the Drag & Drop series to date, here is the complete result of Marcelo's walkthroughs on drag and drop in VB.NET & C#.

  XAML - Window1.xaml
  ______________________________

  <Window x:Class="Window1"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="SampleDragDrop" Height="300" Width="300"
  >
  <Window.Resources>
  <XmlDataProvider x:Key="MyData">
  <x:XData>
  <Sections xmlns="" Title="Library Favorites">
  <Section Name=".NET Development">
  <Article Name="Articles and Overview" />
  <Article Name=".NET Performance" />
  <Article Name="Windows Vista" />
  <Article Name="XML and the .NET Framework" />
  </Section>
  </Sections>
  </x:XData>
  </XmlDataProvider>
  <DataTemplate x:Key="ArticleTemplate">
  <TextBlock FontSize="10pt" Text="{Binding XPath=@Name}" />
  </DataTemplate>
  </Window.Resources>

  
  <DockPanel>

  <Border DockPanel.Dock="Top" BorderBrush="DarkGray" BorderThickness="2" Padding="4">
  <TextBlock FontSize="8pt" FontFamily="Tahoma" TextWrapping="Wrap">
  <Bold>
  Drag Sample
  </Bold>
  <LineBreak />
  <Run>
  This sample demonstrates using a DataObject for dragging "pure" data.
  </Run>
  </TextBlock>
  </Border>

  <ListBox Name="myListBox" AllowDrop="True"
  ItemsSource="{Binding Source={StaticResource MyData}, XPath=/Sections/Section/Article}"
  ItemTemplate="{StaticResource ArticleTemplate}">
  <ListBox.Background>
  <LinearGradientBrush>
  <LinearGradientBrush.GradientStops>
  <GradientStop Color="White" Offset="0" />
  <GradientStop Color="DarkBlue" Offset="1" />
  </LinearGradientBrush.GradientStops>
  </LinearGradientBrush>
  </ListBox.Background>
  </ListBox>

  </DockPanel>
  </Window>

  Code-Behind in C# - Window1.xaml.cs
  ____________________________________________

  public partial class Window1 : Window
  {
  private Point m_StartPoint;
  private bool m_IsDown;
  private System.Xml.XmlElement m_OriginalElement;
  private DropPreviewAdorner m_OverlayElement;
  private System.Xml.XmlElement m_RemoteElement;
  private static DataFormat m_MyFormat = DataFormats.GetDataFormat( "My Love-ly Format" );
  
  public Window1()
  {
  InitializeComponent();
  }

  protected override void OnInitialized( EventArgs e )
  {
  base.OnInitialized( e );

  myListBox.PreviewMouseLeftButtonDown += new System.Windows.Input.MouseButtonEventHandler( MyCanvas_PreviewMouseLeftButtonDown );
  myListBox.PreviewMouseMove += new System.Windows.Input.MouseEventHandler( MyCanvas_PreviewMouseMove );
  myListBox.PreviewDragOver += new DragEventHandler( MyCanvas_PreviewDragOver );
  myListBox.PreviewDrop += new DragEventHandler( MyCanvas_PreviewDrop );
  myListBox.PreviewDragEnter += new DragEventHandler( MyCanvas_PreviewDragEnter );
  myListBox.PreviewDragLeave += new DragEventHandler( MyCanvas_PreviewDragLeave );
  }

  private void MyCanvas_PreviewMouseLeftButtonDown( object sender, System.Windows.Input.MouseButtonEventArgs e )
  {
  m_OriginalElement = GetElementFromPoint( myListBox, e.GetPosition( myListBox ) );
  if ( m_OriginalElement == null )
  {
  return;
  }
  m_IsDown = true;
  m_StartPoint = e.GetPosition( myListBox );
  }

  private System.Xml.XmlElement GetElementFromPoint( ListBox box, Point point )
  {
  UIElement element = (UIElement)box.InputHitTest( point );
  while ( true )
  {
  if ( element == box )
  {
  return null;
  }
  object item = box.ItemContainerGenerator.ItemFromContainer( element );
  bool itemFound = !( item.Equals( DependencyProperty.UnsetValue ) );
  if ( itemFound )
  {
  return item as System.Xml.XmlElement;
  }
  element = (UIElement)VisualTreeHelper.GetParent( element );
  }
  }

  private void MyCanvas_PreviewMouseMove( object sender, System.Windows.Input.MouseEventArgs e )
  {
  if ( m_IsDown )
  {
  if ( Math.Abs( e.GetPosition( myListBox ).X - m_StartPoint.X ) > SystemParameters.MinimumHorizontalDragDistance && Math.Abs( e.GetPosition( myListBox ).Y - m_StartPoint.Y ) > SystemParameters.MinimumVerticalDragDistance )
  {
  DragStarted();
  }
  }
  }

  private void DragStarted()
  {
  m_IsDown = false;
  string serializedObject = m_OriginalElement.OuterXml;
  DataObject data = new DataObject();
  data.SetData( m_MyFormat.Name, serializedObject );
  DragDropEffects effects = DragDrop.DoDragDrop( myListBox, data, DragDropEffects.Copy | DragDropEffects.Move );
  if ( effects == DragDropEffects.Move )
  {
  // Remove the element.
  m_OriginalElement.ParentNode.RemoveChild( m_OriginalElement );
  m_OriginalElement = null;
  }
  }

  private void DragMoved()
  {
  Point currentPosition = System.Windows.Input.Mouse.GetPosition( myListBox );
  m_OverlayElement.LeftOffset = currentPosition.X - m_StartPoint.X;
  m_OverlayElement.TopOffset = currentPosition.Y - m_StartPoint.Y;
  }

  private void MyCanvas_PreviewDragOver( object sender, System.Windows.DragEventArgs e )
  {
  if ( !( UpdateEffects( e ) ) )
  {
  return;
  }
  Point currentPosition = (Point) e.GetPosition( (IInputElement) this.Content );
  m_OverlayElement.LeftOffset = currentPosition.X;
  m_OverlayElement.TopOffset = currentPosition.Y;
  e.Handled = true;
  }

  private void MyCanvas_PreviewDrop( object sender, System.Windows.DragEventArgs e )
  {
  if ( !( UpdateEffects( e ) ) )
  {
  return;
  }
  XmlDataProvider dataProvider = (XmlDataProvider) FindResource( "MyData" );
  System.Xml.XmlDocument document = dataProvider.Document;
  System.Xml.XmlElement node = (System.Xml.XmlElement) dataProvider.Document.ImportNode( m_RemoteElement, true );
  dataProvider.Document.GetElementsByTagName( "Section" )[0].AppendChild(node);
  AdornerLayer.GetAdornerLayer( (System.Windows.Media.Visual) this.Content ).Remove( m_OverlayElement );
  m_RemoteElement = null;
  m_OverlayElement = null;
  e.Handled = true;
  }

  private void MyCanvas_PreviewDragEnter( object sender, System.Windows.DragEventArgs e )
  {
  if ( !( UpdateEffects( e ) ) )
  {
  return;
  }
  string serializedObject = (string) e.Data.GetData( m_MyFormat.Name );
  System.Xml.XmlDocument document = new System.Xml.XmlDocument();
  document.LoadXml( serializedObject );
  m_RemoteElement = document.DocumentElement;
  ContentPresenter presenter = new ContentPresenter();
  presenter.Content = m_RemoteElement;
  presenter.ContentTemplate = myListBox.ItemTemplate;
  AdornerLayer layer;
  m_OverlayElement = new DropPreviewAdorner( (UIElement)this.Content, presenter );
  layer = AdornerLayer.GetAdornerLayer( (System.Windows.Media.Visual) this.Content );
  layer.Add( m_OverlayElement );
  e.Handled = true;
  }

  private void MyCanvas_PreviewDragLeave( object sender, System.Windows.DragEventArgs e )
  {
  if ( m_OverlayElement == null )
  {
  return;
  }
  AdornerLayer.GetAdornerLayer( ( System.Windows.Media.Visual ) this.Content ).Remove( m_OverlayElement );
  m_OverlayElement = null;
  m_RemoteElement = null;
  e.Handled = true;
  }

  private bool UpdateEffects( System.Windows.DragEventArgs e )
  {
  if ( !( e.Data.GetDataPresent( m_MyFormat.Name ) ) )
  {
  e.Effects = DragDropEffects.None;
  return false;
  }
  if ( ( e.AllowedEffects & DragDropEffects.Copy ) == 0 && ( e.AllowedEffects & DragDropEffects.Move ) == 0 )
  {
  e.Effects = DragDropEffects.None;
  return false;
  }
  if ( ( e.AllowedEffects & DragDropEffects.Copy ) != 0 && ( e.AllowedEffects & DragDropEffects.Move ) != 0 )
  {
  if ( ( e.KeyStates & DragDropKeyStates.ControlKey ) != 0 )
  {
  e.Effects = DragDropEffects.Copy;
  }
  else
  {
  e.Effects = DragDropEffects.Move;
  }
  }
  else
  {
  e.Effects = e.AllowedEffects & (( DragDropEffects.Copy | DragDropEffects.Move ) );
  }
  return true;
  }

  #region Adorner Class
  class DropPreviewAdorner : Adorner
  {

  public DropPreviewAdorner( UIElement adornedElement, UIElement adorningElement )
  : base( adornedElement )
  {
  VisualBrush brush = new VisualBrush( adorningElement );
  m_Child = new Rectangle();
  m_Child.Width = adorningElement.RenderSize.Width;
  m_Child.Height = adorningElement.RenderSize.Height;
  m_Child.Fill = brush;
  m_Child.IsHitTestVisible = false;
  System.Windows.Media.Animation.DoubleAnimation animation;
  animation = new System.Windows.Media.Animation.DoubleAnimation( 0.3, 1, new Duration( TimeSpan.FromSeconds( 1 ) ) );
  animation.AutoReverse = true;
  animation.RepeatBehavior = System.Windows.Media.Animation.RepeatBehavior.Forever;
  brush.BeginAnimation( System.Windows.Media.Brush.OpacityProperty, animation );
  }
  private Rectangle m_Child;
  private double m_LeftOffset;
  private double m_TopOffset;

  protected override System.Windows.Size MeasureOverride( System.Windows.Size constraint )
  {
  m_Child.Measure( constraint );
  return m_Child.DesiredSize;
  }

  protected override System.Windows.Size ArrangeOverride( System.Windows.Size finalSize )
  {
  m_Child.Arrange( new Rect( finalSize ) );
  return finalSize;
  }

  protected override System.Windows.Media.Visual GetVisualChild( int index )
  {
  return m_Child;
  }

  protected override int VisualChildrenCount
  {
  get
  {
  return 1;
  }
  }

  public double LeftOffset
  {
  get
  {
  return m_LeftOffset;
  }
  set
  {
  m_LeftOffset = value;
  UpdatePosition();
  }
  }

  public double TopOffset
  {
  get
  {
  return m_TopOffset;
  }
  set
  {
  m_TopOffset = value;
  UpdatePosition();
  }
  }

  private void UpdatePosition()
  {
  AdornerLayer adornerLayer = this.Parent as AdornerLayer;
  if ( adornerLayer != null )
  {
  adornerLayer.Update( AdornedElement );
  }
  }

  public override System.Windows.Media.GeneralTransform GetDesiredTransform( System.Windows.Media.GeneralTransform transform )
  {
  GeneralTransformGroup result = new GeneralTransformGroup();
  result.Children.Add( base.GetDesiredTransform( transform ) );
  result.Children.Add( new TranslateTransform( LeftOffset, TopOffset ) );
  return result;
  }
  }
  #endregion

  Code-Behind in VB.NET - Window1.xaml.vb
  ______________________________________________

  Partial Public Class Window1
  Inherits Window

  Class DropPreviewAdorner
  Inherits Adorner

  Public Sub New(ByVal adornedElement As UIElement, _
  ByVal adorningElement As UIElement)
  MyBase.New(adornedElement)

  Dim brush As VisualBrush = New VisualBrush(adorningElement)

  m_Child = New Rectangle()
  m_Child.Width = adorningElement.RenderSize.Width
  m_Child.Height = adorningElement.RenderSize.Height
  m_Child.Fill = brush
  m_Child.IsHitTestVisible = False

  Dim animation As System.Windows.Media.Animation.DoubleAnimation
  animation = New System.Windows.Media.Animation.DoubleAnimation(0.3, 1, New Duration(TimeSpan.FromSeconds(1)))
  animation.AutoReverse = True
  animation.RepeatBehavior = System.Windows.Media.Animation.RepeatBehavior.Forever
  brush.BeginAnimation(System.Windows.Media.Brush.OpacityProperty, animation)
  End Sub

  ' Adding some basic fields to help us keep track of where we are and what we render
  Private m_Child As Rectangle
  Private m_LeftOffset As Double
  Private m_TopOffset As Double

  Protected Overrides Function MeasureOverride(ByVal constraint As System.Windows.Size) As System.Windows.Size
  m_Child.Measure(constraint)
  Return m_Child.DesiredSize
  End Function

  Protected Overrides Function ArrangeOverride(ByVal finalSize As System.Windows.Size) As System.Windows.Size
  m_Child.Arrange(New Rect(finalSize))
  Return finalSize
  End Function

  Protected Overrides Function GetVisualChild(ByVal index As Integer) As System.Windows.Media.Visual
  Return m_Child
  End Function

  Protected Overrides ReadOnly Property VisualChildrenCount() As Integer
  Get
  Return 1
  End Get
  End Property

  Public Property LeftOffset() As Double
  Get
  Return m_LeftOffset
  End Get
  Set(ByVal value As Double)
  m_LeftOffset = value
  UpdatePosition()
  End Set
  End Property

  Public Property TopOffset() As Double
  Get
  Return m_TopOffset
  End Get
  Set(ByVal value As Double)
  m_TopOffset = value
  UpdatePosition()
  End Set
  End Property

  Private Sub UpdatePosition()
  Dim adornerLayer As AdornerLayer = Me.Parent
  If Not adornerLayer Is Nothing Then
  adornerLayer.Update(AdornedElement)
  End If
  End Sub

  Public Overrides Function GetDesiredTransform(ByVal transform As System.Windows.Media.GeneralTransform) As System.Windows.Media.GeneralTransform
  Dim result As GeneralTransformGroup = New GeneralTransformGroup()
  result.Children.Add(MyBase.GetDesiredTransform(transform))
  result.Children.Add(New TranslateTransform(LeftOffset, TopOffset))
  Return result
  End Function

  End Class

  Private m_StartPoint As Point ' Where did the mouse start off from
  Private m_IsDown As Boolean ' Is the mouse down right now
  Private m_OriginalElement As System.Xml.XmlElement ' What is it that we're dragging
  Private m_OverlayElement As DropPreviewAdorner ' What is it that we're using to show
  Private m_RemoteElement As System.Xml.XmlElement
  Private Shared m_MyFormat As DataFormat = DataFormats.GetDataFormat("My Love-ly Format")

  Public Sub New()
  InitializeComponent()
  End Sub

  Private Sub myListBox_PreviewMouseLeftButtonDown(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Handles myListBox.PreviewMouseLeftButtonDown
  m_OriginalElement = GetElementFromPoint(myListBox, e.GetPosition(myListBox))
  If m_OriginalElement Is Nothing Then Exit Sub
  m_IsDown = True
  m_StartPoint = e.GetPosition(myListBox)
  End Sub

  Private Function GetElementFromPoint(ByVal box As ListBox, ByVal point As Point) As System.Xml.XmlElement
  Dim element As UIElement = box.InputHitTest(point)
  While True
  If element Is box Then Return Nothing
  Dim item As Object = box.ItemContainerGenerator.ItemFromContainer(element)
  Dim itemFound As Boolean = Not item.Equals(DependencyProperty.UnsetValue)
  If itemFound Then Return item
  element = VisualTreeHelper.GetParent(element)
  End While
  Return Nothing
  End Function

  Private Sub myListBox_PreviewMouseMove(ByVal sender As Object, ByVal e As System.Windows.Input.MouseEventArgs) Handles myListBox.PreviewMouseMove
  If m_IsDown Then
  If Math.Abs(e.GetPosition(myListBox).X - m_StartPoint.X) > SystemParameters.MinimumHorizontalDragDistance AndAlso _
  Math.Abs(e.GetPosition(myListBox).Y - m_StartPoint.Y) > SystemParameters.MinimumVerticalDragDistance Then
  DragStarted()
  End If
  End If
  End Sub

  Private Sub DragStarted()
  m_IsDown = False

  Dim serializedObject As String = m_OriginalElement.OuterXml
  Dim data As DataObject = New DataObject()
  data.SetData(m_MyFormat.Name, serializedObject)
  Dim effects As DragDropEffects = _
  DragDrop.DoDragDrop(myListBox, data, DragDropEffects.Copy Or DragDropEffects.Move)
  If effects And DragDropEffects.Move Then
  ' Remove the element.
  m_OriginalElement.ParentNode.RemoveChild(m_OriginalElement)
  m_OriginalElement = Nothing
  End If
  End Sub

  Private Sub DragMoved()
  Dim currentPosition As Point = System.Windows.Input.Mouse.GetPosition(myListBox)
  m_OverlayElement.LeftOffset = currentPosition.X - m_StartPoint.X
  m_OverlayElement.TopOffset = currentPosition.Y - m_StartPoint.Y
  End Sub

  Private Sub myListBox_PreviewDragOver(ByVal sender As Object, ByVal e As System.Windows.DragEventArgs) Handles myListBox.PreviewDragOver
  If Not UpdateEffects(e) Then
  Exit Sub
  End If

  Dim currentPosition As Point = e.GetPosition(Me.Content)
  m_OverlayElement.LeftOffset = currentPosition.X
  m_OverlayElement.TopOffset = currentPosition.Y

  e.Handled = True
  End Sub

  Private Sub myListBox_PreviewDrop(ByVal sender As Object, ByVal e As System.Windows.DragEventArgs) Handles myListBox.PreviewDrop
  If Not UpdateEffects(e) Then
  Exit Sub
  End If

  ' Add the element.
  Dim dataProvider As XmlDataProvider = FindResource("MyData")
  Dim document As System.Xml.XmlDocument = dataProvider.Document
  Dim node As System.Xml.XmlElement = dataProvider.Document.ImportNode(m_RemoteElement, True)
  dataProvider.Document.GetElementsByTagName("Section")(0).AppendChild(node)

  ' Cleanup
  AdornerLayer.GetAdornerLayer(Me.Content).Remove(m_OverlayElement)
  m_RemoteElement = Nothing
  m_OverlayElement = Nothing

  e.Handled = True
  End Sub

  Private Sub myListBox_PreviewDragEnter(ByVal sender As Object, ByVal e As System.Windows.DragEventArgs) Handles myListBox.PreviewDragEnter
  If Not UpdateEffects(e) Then
  Exit Sub
  End If

  ' First, we deserialize the object provided to us.
  Dim serializedObject As String = e.Data.GetData(m_MyFormat.Name)
  Dim document As System.Xml.XmlDocument = New System.Xml.XmlDocument()
  document.LoadXml(serializedObject)
  m_RemoteElement = document.DocumentElement

  ' Now, create something we can render with.
  Dim presenter As ContentPresenter = New ContentPresenter()
  presenter.Content = m_RemoteElement
  presenter.ContentTemplate = myListBox.ItemTemplate

  ' Next, create an adorner for it.
  Dim layer As AdornerLayer
  m_OverlayElement = New DropPreviewAdorner(Me.Content, presenter)
  layer = AdornerLayer.GetAdornerLayer(Me.Content)
  layer.Add(m_OverlayElement)

  e.Handled = True
  End Sub

  Private Sub myListBox_PreviewDragLeave(ByVal sender As Object, ByVal e As System.Windows.DragEventArgs) Handles myListBox.PreviewDragLeave
  If m_OverlayElement Is Nothing Then Exit Sub

  AdornerLayer.GetAdornerLayer(Me.Content).Remove(m_OverlayElement)
  m_OverlayElement = Nothing
  m_RemoteElement = Nothing

  e.Handled = True
  End Sub

  Private Function UpdateEffects(ByVal e As System.Windows.DragEventArgs) As Boolean
  ' If we don't know what we're talking about, we shouldn't do anything.
  If Not e.Data.GetDataPresent(m_MyFormat.Name) Then
  e.Effects = DragDropEffects.None
  Return False
  End If

  ' If we can't copy or move, we shouldn't do anything (eg: provider wants us to link).
  If (e.AllowedEffects And DragDropEffects.Copy) = 0 AndAlso _
  (e.AllowedEffects And DragDropEffects.Move) = 0 Then
  e.Effects = DragDropEffects.None
  Return False
  End If

  ' Figure out whether we should copy or move. If we can do either, we'll move unless
  ' Ctrl is pressed.
  If (e.AllowedEffects And DragDropEffects.Copy) <> 0 AndAlso _
  (e.AllowedEffects And DragDropEffects.Move) <> 0 Then
  If (e.KeyStates And DragDropKeyStates.ControlKey) <> 0 Then
  e.Effects = DragDropEffects.Copy
  Else
  e.Effects = DragDropEffects.Move
  End If
  Else
  e.Effects = e.AllowedEffects And Not (DragDropEffects.Copy Or DragDropEffects.Move)
  End If
  Return True
  End Function

  End Class

  
  

• Drak Swordsman

  You might want to take a look at Mercelo's blog, there are at least 2 or 3 examples of drag and drop, the latest particularly looks alot like what your looking for.

  http://blogs.msdn.com/marcelolr/archive/category/11786.aspx

  
  

• HowardCarr

  Thanks marcelo, i look forward to it.
  

• Hal T

  Thanks for the response but marcelo's example seems to be incomplete, i tried to reconstruct it but he declares a variable of type DropPreviewAdorner which does not exist as far as i can see... as i mentioned i am running the feb ctp so perhaps that's the reason but i'd still like to see some code that works on it if anyone has it.

  
  
• drag and drop between list boxes