/// <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 ToolboxTreeNodeModel;
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:
// When dropping before or after, a new node will be inserted as a child to the parent of the target
var nav = targetControl.GetItemNavigator(targetItem);
if (nav != null)
{
// Cache the original target
var targetChildModel = targetModel;
// Quit if unable to move to navigate to the parent
if (!nav.GoToParent())
{
return;
}
// Update the target item to be the parent of the original target
targetItem = nav.CurrentItem;
targetModel = targetItem as ToolboxTreeNodeModel;
// Quit if the new target is not the expected model
if (targetModel == null)
{
return;
}
// Resolve index of the new node based on whether it should be before
// or after the original target.
var index = targetModel.Children.IndexOf(targetChildModel);
if (index != -1)
{
targetDropIndex = index + (dropArea == TreeItemDropArea.After ? 1 : 0);
}
}
break;
}
// Resolve the category for the drop target
if (!TryGetCategory(targetControl, targetModel, out var targetCategoryModel))
{
MessageBox.Show("Unable to determine the drop category.", "Drag and Drop", MessageBoxButton.OK);
return;
}
// Get the dragged controls (only control nodes are currently supported)
List <ControlTreeNodeModel> sourceControlModels = GetDraggedModels(e.Data, targetControl)
.OfType <ControlTreeNodeModel>()
.ToList();
if (sourceControlModels.Count > 0)
{
// Check each item and validate that various drop operations are allowed before actually executing the drop
foreach (var sourceModel in sourceControlModels)
{
if (sourceModel == targetModel)
{
MessageBox.Show("Cannot drop an item on itself.", "Drag and Drop", MessageBoxButton.OK);
return;
}
else
{
var nav = targetControl.GetItemNavigator(sourceModel);
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 == sourceModel)
{
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;
}
else if ((originalEffects & DragDropEffects.Copy) == DragDropEffects.Copy)
{
e.Effects = DragDropEffects.Copy;
e.Handled = true;
}
if (IsFavoritesCategory(targetCategoryModel))
{
// Controls dragged into favorites category will not actually be moved. They will be added as favorites.
foreach (var sourceControlModel in sourceControlModels)
{
sourceControlModel.IsFavorite = true;
}
}
else
{
// Complete operation
bool isMove = e.Effects == DragDropEffects.Move;
foreach (var sourceControlModel in sourceControlModels)
{
// Resolve the source category of the dragged control
if (!TryGetCategory(targetControl, sourceControlModel, out var sourceCategoryModel))
{
break;
}
if (isMove)
{
// Remove the control from the original category
var index = sourceCategoryModel.Children.IndexOf(sourceControlModel);
if (index != -1)
{
if ((sourceCategoryModel == targetCategoryModel) && (index < targetDropIndex))
{
targetDropIndex--;
}
sourceCategoryModel.Children.RemoveAt(index);
}
else
{
// Quit processing if any source cannot be located
break;
}
// Add the control to the new category (may be the same as the source if it was repositioned)
int resolvedTargetDropIndex = Math.Max(0, Math.Min(targetCategoryModel.Children.Count, targetDropIndex++));
targetCategoryModel.Children.Insert(resolvedTargetDropIndex, sourceControlModel);
targetCategoryModel.IsExpanded = true;
// Focus the last item that was moved
if (sourceControlModels[sourceControlModels.Count - 1] == sourceControlModel)
{
// Must dispatch the focus changes to allow the view to update based on changes in the models
Dispatcher.CurrentDispatcher.BeginInvoke((Action)(() => {
targetControl.FocusItem(sourceControlModel);
}), DispatcherPriority.Normal);
}
}
}
}
}
}
}
/// <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 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, item data present, and the drop target is recognized...
if ((dropArea != TreeItemDropArea.None) &&
(e.Data.GetDataPresent(TreeListBox.ItemDataFormat)) &&
(TryGetModelsFromItem(targetControl, targetItem, out var targetCategoryModel, out _)))
{
// Locate the dragged model. If multiple objects were selected, only the first object is used for reference.
// The dragged item must be defined in the target control for the drag operation to be allowed.
var sourceItem = GetDraggedModels(e.Data, targetControl).FirstOrDefault();
if ((sourceItem != null) && (TryGetModelsFromItem(targetControl, sourceItem, out var sourceCategoryModel, out _)))
{
if (IsFavoritesCategory(sourceCategoryModel))
{
// Dragging from the "Favorites" category is not supported within the Toolbox control. Favorites can only
// be dragged outside of the control (i.e. to the designer surface).
e.Effects = DragDropEffects.None;
e.Handled = true;
}
else if (IsFavoritesCategory(targetCategoryModel))
{
// Dropping on the "Favorites" category will only change if the control is a favorite and will not
// alter the location of the source control in the toolbox, so use the 'Copy' effect.
if ((e.AllowedEffects & DragDropEffects.Copy) == DragDropEffects.Copy)
{
e.Effects = DragDropEffects.Copy;
e.Handled = true;
}
}
else
{
// Controls cannot exist in more than one category, so only move effect is allowed
if ((e.AllowedEffects & DragDropEffects.Move) == DragDropEffects.Move)
{
e.Effects = DragDropEffects.Move;
e.Handled = true;
}
}
if ((e.Handled) && (e.Effects != DragDropEffects.None))
{
// TreeItems can be dropped 'Before', 'On', or 'After' a target node, but drop targets may not support
// all of these scenarios. Coerce the drop area, as needed, based on the target node.
if (targetItem is CategoryTreeNodeModel)
{
// Since controls can only be children to a category, not siblings, coerce all drops to 'On'
dropArea = TreeItemDropArea.On;
}
else if (targetItem is EmptyPlaceholderTreeNodeModel)
{
// When the control is dropped, the empty placeholder will be remove and the dropped control
// will be added as first child to the category, so coerce all drops to 'Before' the placeholder.
dropArea = TreeItemDropArea.Before;
}
else if ((targetItem is ControlTreeNodeModel) && (dropArea == TreeItemDropArea.On))
{
// A control cannot have children, so coerce dropping 'On' a control to 'After' (i.e. next sibling)
dropArea = TreeItemDropArea.After;
}
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);
}
}
}
}
}
}
}