Differences

This shows you the differences between two versions of the page.

--- swdev:dotnet:drag_and_drop [2010/11/15 14:35]
smayr
+++ swdev:dotnet:drag_and_drop [2011/04/06 08:44] (current)
smayr
@@ Line 2: / Line 2: @@
 == Source Control (Drag Origin) ==
+Sample ListBox (XAML) where Drag originates:
+<code xml>
+<ListBox Name="lstEnvironments"
+               SelectionChanged="lstEnvironments_SelectionChanged"
+               PreviewMouseLeftButtonDown="lstEnvironments_PreviewMouseLeftButtonDown"
+               MouseMove="lstEnvironments_MouseMove">
+          <ListBoxItem>Normal</ListBoxItem>
+          <ListBoxItem>Restaurant/Party</ListBoxItem>
+          <ListBoxItem>Telephone</ListBoxItem>
+          <ListBoxItem>Music</ListBoxItem>
+</ListBox>
+</code>
+Code behind:
+<code csharp>
+private void lstEnvironments_SelectionChanged(object sender, SelectionChangedEventArgs e)
+{
+    string myDragData = ((ListBoxItem)lstEnvironments.SelectedItem).Content.ToString();
+    lblSelectedEnvironment.Text = string.Format("{0}", myDragData);  // selected data
+}
+private void lstEnvironments_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
+{
+    // Store the mouse position
+    startPoint = e.GetPosition(null);
+}
+private void lstEnvironments_MouseMove(object sender, MouseEventArgs e)
+{
+    // Get the current mouse position
+    Point mousePos = e.GetPosition(null);
+    Vector diff = startPoint - mousePos;
+    if (e.LeftButton == MouseButtonState.Pressed &&
+        Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance &&
+        Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)
+    {
+        // Get the dragged ListBoxItem
+        ListBox lstBox = sender as ListBox;
+        ListBoxItem lstBoxItem = FindAnchestor<ListBoxItem>((DependencyObject)e.OriginalSource);
+        // Find the data behind the ListBoxItem
+        //string str = (string)lstBox.ItemContainerGenerator.ItemFromContainer(lstBoxItem);
+        string str = ((ListBoxItem)lstBox.SelectedItem).Content.ToString();
+        // Initialize the drag & drop operation
+        DataObject dragData = new DataObject(typeof(string), str);
+        DragDrop.DoDragDrop(lstBoxItem, dragData, DragDropEffects.Move);
+    }
+}
+// Helper to search up the VisualTree
+private static T FindAnchestor<T>(DependencyObject current)
+    where T : DependencyObject
+{
+    do
+    {
+        if (current is T)
+        {
+            return (T)current;
+        }
+        current = VisualTreeHelper.GetParent(current);
+    }
+    while (current != null);
+    return null;
+}
+</code>
 == Target Control (Drop Target) ==
+Target controls where Drop is performed.  In this case, a ''ListBox'', ''TextBlock'', and ''TextBox''.
+<code xml>
+<TextBlock FontWeight="Bold" Margin="0,10,0,0">Dragged Items</TextBlock>
+<TextBlock>ListBox:</TextBlock>
+<ListBox Name="lstAppliedEnvironment" AllowDrop="True" Height="100"  SelectionMode="Single"
+         DragEnter="lstAppliedEnvironment_DragEnter"
+         Drop="lstAppliedEnvironment_Drop">
+</ListBox>
+<StackPanel Orientation="Horizontal">
+    <TextBlock>TextBlock:</TextBlock>
+    <TextBlock Name="lblAppliedEnvironment" Margin="5,0,0,20" AllowDrop="True"
+           DragEnter="lblAppliedEnvironment_DragEnter" Drop="lblApliedEnvironment_Drop">Value</TextBlock>
+</StackPanel>
+<TextBox Name="txtAppliedEnvironment" Height="30" AllowDrop="True"
+         DragEnter="txtSelectedEnvironment_DragEnter"
+         Drop="txtAppliedEnvironment_Drop"></TextBox>
+</code>
+Code behind:
+<code csharp>
+private void lstAppliedEnvironment_DragEnter(object sender, DragEventArgs e)
+{
+    if (!e.Data.GetDataPresent("str") || sender == e.Source)
+    {
+        e.Effects = DragDropEffects.None;
+    }
+}
+private void lstAppliedEnvironment_Drop(object sender, DragEventArgs e)
+{
+    if (e.Data.GetDataPresent(typeof(string)))
+    {
+        string str = e.Data.GetData(typeof(string)) as string;
+        ListBox lstBox = sender as ListBox;
+        lstBox.Items.Add(str);
+    }
+}
+private void lblAppliedEnvironment_DragEnter(object sender, DragEventArgs e)
+{
+    if (!e.Data.GetDataPresent("str") || sender == e.Source)
+    {
+        e.Effects = DragDropEffects.None;
+    }
+}
+private void lblAppliedEnvironment_Drop(object sender, DragEventArgs e)
+{
+    if (e.Data.GetDataPresent(typeof(string)))
+    {
+        string str = e.Data.GetData(typeof(string)) as string;
+        TextBlock lbl = sender as TextBlock;
+        lbl.Text = str;
+    }
+}
+</code>
 == Resources ==
   * [[http://blog.nostatic.org/2007/12/drag-and-drop-in-wpf.html|Drag and Drop in WPF]]
-  * [[http://blogs.msdn.com/b/jaimer/archive/2007/07/12/drag-drop-in-wpf-explained-end-to-end.aspx|Drag and Drop in WPF Explained End to End]]
+  * [[http://blogs.msdn.com/b/jaimer/archive/2007/07/12/drag-drop-in-wpf-explained-end-to-end.aspx|Drag and Drop in WPF Explained End to End]] (Jaime Rodríguez)
   * [[http://msdn.microsoft.com/en-us/library/ms742859.aspx|MSDN: Drag and Drop Overview]]
   * [[http://wpftutorial.net/DragAndDrop.html|WPF Tutorial: Drag and Drop]]
+  * [[http://www.switchonthecode.com/tutorials/winforms-using-custom-cursors-with-drag-drop|WinForms using custom cursors with Drag and Drop]]
+  * [[http://www.codeproject.com/KB/WPF/DraggingElementsInCanvas.aspx|Dragging Elements in Canvas]]