/// <summary>
/// Gets an enumerable of all dragged items.
/// </summary>
/// <param name="dataObject">The <see cref="IDataObject"/> which defines the dragged items.</param>
/// <param name="control">The control from which items will be derived.</param>
/// <returns>Returns an enumerable of all dragged items which will be empty if no items were found.</returns>
internal static IEnumerable <ToolboxTreeNodeModel> GetDraggedModels(IDataObject dataObject, TreeListBox control)
{
string format = TreeListBox.ItemDataFormat;
if (dataObject.GetDataPresent(format))
{
string data = dataObject.GetData(format) as string;
if (!string.IsNullOrWhiteSpace(data))
{
foreach (var fullPath in SplitItemFullPaths(data))
{
if (control.GetItemByFullPath(fullPath) is ToolboxTreeNodeModel itemModel)
{
yield return(itemModel);
}
}
}
}
}
/// <summary>
/// Notifies that a drag event occurred over a target item, requests that appropriate updates are made to the supplied <c>DragEventArgs</c>,
/// and requests that the allowed drop area is returned for visual target feedback.
/// </summary>
/// <param name="e">The <see cref="DragEventArgs"/> whose effects should be updated.</param>
/// <param name="targetControl">The target control, over which the event occurred</param>
/// <param name="targetItem">The target item, which could be <see langword="null"/> if dragging below the last tree item.</param>
/// <param name="dropArea">A <see cref="TreeItemDropArea"/> indicating the drop area over the target item.</param>
/// <returns>
/// A <see cref="TreeItemDropArea"/> indicating the allowed drop area, which will be used for visual feedback to the end user.
/// Return <c>TreeItemDropArea.None</c> for no visual feedback.
/// </returns>
/// <remarks>
/// The default implementation of this method sets the <c>e.Effects</c> to <c>DragDropEffects.None</c> and returns that no drop area is allowed.
/// Override this method if you wish to support dropping and add logic to properly handle the dragged data.
/// </remarks>
public override TreeItemDropArea OnDragOver(DragEventArgs e, TreeListBox targetControl, object targetItem, TreeItemDropArea dropArea)
{
// If the drag is over an item and there is item data present...
if ((targetItem != null) && (dropArea != TreeItemDropArea.None) && (e.Data.GetDataPresent(TreeListBox.ItemDataFormat)))
{
var fullPaths = e.Data.GetData(TreeListBox.ItemDataFormat) as string;
if (!string.IsNullOrEmpty(fullPaths))
{
// Locate the first item based on full path
object firstItem = null;
foreach (var fullPath in fullPaths.Split(new char[] { '\r', '\n' }))
{
if (!string.IsNullOrEmpty(fullPath))
{
var item = targetControl.GetItemByFullPath(fullPath);
if (item != null)
{
firstItem = item;
break;
}
}
}
if (firstItem != null)
{
// Ensure that the first item is already in the target control (nav will be null if not)... if allowing drag/drop onto external
// controls, you cannot use the item navigator and must rely on your own item hierarchy logic
var firstItemNav = targetControl.GetItemNavigator(firstItem);
if (firstItemNav != null)
{
// Only support a single effect (you could add support for other effects like Copy if the Ctrl key is down here)
if ((e.AllowedEffects & DragDropEffects.Move) == DragDropEffects.Move)
{
e.Effects = DragDropEffects.Move;
e.Handled = true;
}
switch (e.Effects)
{
case DragDropEffects.Move:
// Coerce the resulting drop-area so that if dragging 'after' an item that has a next sibling, the drop area
// becomes 'on' the item instead... can still get between the items by dragging 'before' the next sibling in this scenario
if (dropArea == TreeItemDropArea.After)
{
var targetItemNav = targetControl.GetItemNavigator(targetItem);
if ((targetItemNav != null) && (targetItemNav.GoToNextSibling()))
{
dropArea = TreeItemDropArea.On;
}
}
return(dropArea);
}
}
}
}
}
e.Effects = DragDropEffects.None;
return(TreeItemDropArea.None);
}
/// <summary>
/// Notifies that a drop event occurred over a target item and requests that appropriate updates are made to the supplied <c>DragEventArgs</c>.
/// </summary>
/// <param name="e">The <see cref="DragEventArgs"/> whose effects should be updated.</param>
/// <param name="targetControl">The target control, over which the event occurred</param>
/// <param name="targetItem">The target item, which could be <see langword="null"/> if dragging below the last tree item.</param>
/// <param name="dropArea">A <see cref="TreeItemDropArea"/> indicating the drop area over the target item.</param>
/// <remarks>
/// The default implementation of this method sets the <c>e.Effects</c> to <c>DragDropEffects.None</c> and takes no further action.
/// Override this method if you wish to support dropping and add logic to properly handle the dragged data.
/// </remarks>
public override void OnDrop(DragEventArgs e, TreeListBox targetControl, object targetItem, TreeItemDropArea dropArea)
{
var originalEffects = e.Effects;
e.Effects = DragDropEffects.None;
// If the drag is over an item and there is item data present...
var targetModel = targetItem as TreeNodeModel;
if ((targetModel != null) && (dropArea != TreeItemDropArea.None) && (e.Data.GetDataPresent(TreeListBox.ItemDataFormat)))
{
// Resolve the real target item (in case the drop area is above or below the target item)
var targetDropIndex = targetModel.Children.Count;
switch (dropArea)
{
case TreeItemDropArea.Before:
case TreeItemDropArea.After:
var nav = targetControl.GetItemNavigator(targetItem);
if (nav != null)
{
var targetChildModel = targetModel;
var targetChildItem = targetItem;
if (!nav.GoToParent())
{
return;
}
targetItem = nav.CurrentItem;
targetModel = targetItem as TreeNodeModel;
if (targetModel == null)
{
return;
}
var index = targetModel.Children.IndexOf(targetChildModel);
if (index != -1)
{
targetDropIndex = index + (dropArea == TreeItemDropArea.After ? 1 : 0);
}
}
break;
}
// Get the items
var fullPaths = e.Data.GetData(TreeListBox.ItemDataFormat) as string;
if (!string.IsNullOrEmpty(fullPaths))
{
// Locate items based on full path
var items = new List <object>();
foreach (var fullPath in fullPaths.Split(new char[] { '\r', '\n' }))
{
if (!string.IsNullOrEmpty(fullPath))
{
var item = targetControl.GetItemByFullPath(fullPath);
if (item != null)
{
items.Add(item);
}
}
}
if (items.Count > 0)
{
// Check each item and validate that various drop operations are allowed before actually executing the drop
foreach (var item in items)
{
if (item == targetItem)
{
MessageBox.Show("Cannot drop an item on itself.", "Drag and Drop", MessageBoxButton.OK);
return;
}
else
{
var nav = targetControl.GetItemNavigator(item);
if (nav == null)
{
MessageBox.Show("Cannot drop from a different control.", "Drag and Drop", MessageBoxButton.OK);
return;
}
else
{
if (nav.GoToCommonAncestor(targetItem))
{
if (nav.CurrentItem == item)
{
MessageBox.Show("Cannot drop onto a descendant item.", "Drag and Drop", MessageBoxButton.OK);
return;
}
}
}
}
}
// Only support a single effect (you could add support for other effects like Copy if the Ctrl key is down here)
if ((originalEffects & DragDropEffects.Move) == DragDropEffects.Move)
{
e.Effects = DragDropEffects.Move;
e.Handled = true;
}
// Move items
foreach (var item in items)
{
var nav = targetControl.GetItemNavigator(item);
if (nav.GoToParent())
{
var itemModel = item as TreeNodeModel;
var parentModel = nav.CurrentItem as TreeNodeModel;
if ((itemModel != null) && (parentModel != null))
{
var index = parentModel.Children.IndexOf(itemModel);
if (index != -1)
{
if ((parentModel == targetModel) && (index < targetDropIndex))
{
targetDropIndex--;
}
parentModel.Children.RemoveAt(index);
}
else
{
break;
}
}
else
{
break;
}
targetModel.Children.Insert(Math.Max(0, Math.Min(targetModel.Children.Count, targetDropIndex++)), itemModel);
targetModel.IsExpanded = true;
// Focus the last item
if (items[items.Count - 1] == item)
{
targetControl.FocusItem(itemModel);
}
}
}
}
}
}
}
