private static void DragSource_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
// Ignore the click if the user has clicked on a scrollbar.
if (HitTestScrollBar(sender, e))
{
_dragInfo = null;
return;
}
_dragInfo = new DragInfo(sender, e);
// If the sender is a list box that allows multiple selections, ensure that clicking on an
// already selected item does not change the selection, otherwise dragging multiple items
// is made impossible.
var itemsControl = sender as ItemsControl;
if (_dragInfo.VisualSourceItem == null || itemsControl == null || !itemsControl.CanSelectMultipleItems())
{
return;
}
var selectedItems = itemsControl
.GetSelectedItems()
.Cast <object>()
.ToList();
if (selectedItems.Count() <= 1 || !selectedItems.Contains(_dragInfo.SourceItem))
{
return;
}
_clickSupressItem = _dragInfo.SourceItem;
e.Handled = true;
}
/// <summary>
/// Initializes a new instance of the DropInfo class.
/// </summary>
/// <param name="sender">
/// The sender of the drag event.
/// </param>
/// <param name="e">
/// The drag event.
/// </param>
/// <param name="dragInfo">
/// Information about the source of the drag, if the drag came from within the framework.
/// </param>
public DropInfo(object sender, DragEventArgs e, DragInfo dragInfo)
{
string dataFormat = DragDrop.DataFormat.Name;
Data = (e.Data.GetDataPresent(dataFormat)) ? e.Data.GetData(dataFormat) : e.Data;
DragInfo = dragInfo;
VisualTarget = sender as UIElement;
if (VisualTarget == null)
return;
DropPosition = e.GetPosition(VisualTarget);
if (!(sender is ItemsControl))
return;
var itemsControl = (ItemsControl)sender;
UIElement item = itemsControl.GetItemContainerAt(DropPosition);
bool directlyOverItem = item != null;
TargetGroup = FindGroup(itemsControl, DropPosition);
VisualTargetOrientation = itemsControl.GetItemsPanelOrientation();
if (item == null)
{
item = itemsControl.GetItemContainerAt(DropPosition, VisualTargetOrientation);
directlyOverItem = false;
}
if (item == null)
{
TargetCollection = itemsControl.ItemsSource ?? itemsControl.Items;
InsertIndex = itemsControl.Items.Count;
return;
}
ItemsControl itemParent = ItemsControl.ItemsControlFromItemContainer(item);
InsertIndex = itemParent.ItemContainerGenerator.IndexFromContainer(item);
TargetCollection = itemParent.ItemsSource ?? itemParent.Items;
if (directlyOverItem)
{
TargetItem = itemParent.ItemContainerGenerator.ItemFromContainer(item);
VisualTargetItem = item;
}
if (VisualTargetOrientation == Orientation.Vertical)
{
if (e.GetPosition(item).Y > item.RenderSize.Height / 2)
InsertIndex++;
}
else
{
if (e.GetPosition(item).X > item.RenderSize.Width / 2)
InsertIndex++;
}
}
private static void DragSource_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (_dragInfo == null || _dragInProgress)
{
return;
}
Point dragStart = _dragInfo.DragStartPosition;
Point position = e.GetPosition(null);
if (Math.Abs(position.X - dragStart.X) <= SystemParameters.MinimumHorizontalDragDistance &&
Math.Abs(position.Y - dragStart.Y) <= SystemParameters.MinimumVerticalDragDistance)
{
return;
}
IDragSource dragHandler = GetDragHandler(_dragInfo.VisualSource);
if (dragHandler != null)
{
dragHandler.StartDrag(_dragInfo);
}
else
{
DefaultDragHandler.StartDrag(_dragInfo);
}
if (_dragInfo.Effects == DragDropEffects.None || _dragInfo.Data == null)
{
return;
}
var data = new DataObject(DataFormat.Name, _dragInfo.Data);
try
{
_dragInProgress = true;
System.Windows.DragDrop.DoDragDrop(_dragInfo.VisualSource, data, _dragInfo.Effects);
}
finally
{
_dragInProgress = false;
}
_dragInfo = null;
}
private static void DragSource_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
// If we prevented the control's default selection handling in DragSource_PreviewMouseLeftButtonDown
// by setting 'e.Handled = true' and a drag was not initiated, manually set the selection here.
var itemsControl = sender as ItemsControl;
if (itemsControl != null && _dragInfo != null && _clickSupressItem == _dragInfo.SourceItem)
{
if ((Keyboard.Modifiers & ModifierKeys.Control) != 0)
{
itemsControl.SetItemSelected(_dragInfo.SourceItem, false);
}
else
{
itemsControl.SetSelectedItem(_dragInfo.SourceItem);
}
}
_dragInfo = null;
_clickSupressItem = null;
}
/// <summary>
/// Initializes a new instance of the DropInfo class.
/// </summary>
/// <param name="sender">
/// The sender of the drag event.
/// </param>
/// <param name="e">
/// The drag event.
/// </param>
/// <param name="dragInfo">
/// Information about the source of the drag, if the drag came from within the framework.
/// </param>
public DropInfo(object sender, DragEventArgs e, DragInfo dragInfo)
{
string dataFormat = DragDrop.DataFormat.Name;
Data = (e.Data.GetDataPresent(dataFormat)) ? e.Data.GetData(dataFormat) : e.Data;
DragInfo = dragInfo;
VisualTarget = sender as UIElement;
if (VisualTarget == null)
{
return;
}
DropPosition = e.GetPosition(VisualTarget);
if (!(sender is ItemsControl))
{
return;
}
var itemsControl = (ItemsControl)sender;
UIElement item = itemsControl.GetItemContainerAt(DropPosition);
bool directlyOverItem = item != null;
TargetGroup = FindGroup(itemsControl, DropPosition);
VisualTargetOrientation = itemsControl.GetItemsPanelOrientation();
if (item == null)
{
item = itemsControl.GetItemContainerAt(DropPosition, VisualTargetOrientation);
directlyOverItem = false;
}
if (item == null)
{
TargetCollection = itemsControl.ItemsSource ?? itemsControl.Items;
InsertIndex = itemsControl.Items.Count;
return;
}
ItemsControl itemParent = ItemsControl.ItemsControlFromItemContainer(item);
InsertIndex = itemParent.ItemContainerGenerator.IndexFromContainer(item);
TargetCollection = itemParent.ItemsSource ?? itemParent.Items;
if (directlyOverItem)
{
TargetItem = itemParent.ItemContainerGenerator.ItemFromContainer(item);
VisualTargetItem = item;
}
if (VisualTargetOrientation == Orientation.Vertical)
{
if (e.GetPosition(item).Y > item.RenderSize.Height / 2)
{
InsertIndex++;
}
}
else
{
if (e.GetPosition(item).X > item.RenderSize.Width / 2)
{
InsertIndex++;
}
}
}
private static void DragSource_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (_dragInfo == null || _dragInProgress)
return;
Point dragStart = _dragInfo.DragStartPosition;
Point position = e.GetPosition(null);
if (Math.Abs(position.X - dragStart.X) <= SystemParameters.MinimumHorizontalDragDistance &&
Math.Abs(position.Y - dragStart.Y) <= SystemParameters.MinimumVerticalDragDistance)
return;
IDragSource dragHandler = GetDragHandler(_dragInfo.VisualSource);
if (dragHandler != null)
dragHandler.StartDrag(_dragInfo);
else
DefaultDragHandler.StartDrag(_dragInfo);
if (_dragInfo.Effects == DragDropEffects.None || _dragInfo.Data == null)
return;
var data = new DataObject(DataFormat.Name, _dragInfo.Data);
try
{
_dragInProgress = true;
System.Windows.DragDrop.DoDragDrop(_dragInfo.VisualSource, data, _dragInfo.Effects);
}
finally
{
_dragInProgress = false;
}
_dragInfo = null;
}
private static void DragSource_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
// If we prevented the control's default selection handling in DragSource_PreviewMouseLeftButtonDown
// by setting 'e.Handled = true' and a drag was not initiated, manually set the selection here.
var itemsControl = sender as ItemsControl;
if (itemsControl != null && _dragInfo != null && _clickSupressItem == _dragInfo.SourceItem)
{
if ((Keyboard.Modifiers & ModifierKeys.Control) != 0)
itemsControl.SetItemSelected(_dragInfo.SourceItem, false);
else
itemsControl.SetSelectedItem(_dragInfo.SourceItem);
}
_dragInfo = null;
_clickSupressItem = null;
}
private static void DragSource_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
// Ignore the click if the user has clicked on a scrollbar.
if (HitTestScrollBar(sender, e))
{
_dragInfo = null;
return;
}
_dragInfo = new DragInfo(sender, e);
// If the sender is a list box that allows multiple selections, ensure that clicking on an
// already selected item does not change the selection, otherwise dragging multiple items
// is made impossible.
var itemsControl = sender as ItemsControl;
if (_dragInfo.VisualSourceItem == null || itemsControl == null || !itemsControl.CanSelectMultipleItems())
return;
var selectedItems = itemsControl
.GetSelectedItems()
.Cast<object>()
.ToList();
if (selectedItems.Count() <= 1 || !selectedItems.Contains(_dragInfo.SourceItem))
return;
_clickSupressItem = _dragInfo.SourceItem;
e.Handled = true;
}
