// DragSource
private void DragSource_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
this.sourceItemsControl = (ItemsControl)sender;
Visual visual = e.OriginalSource as Visual;
this.topWindow = (Window)DragDropUtilities.FindAncestor(typeof(Window), this.sourceItemsControl);
this.initialMousePosition = e.GetPosition(this.topWindow);
this.sourceItemContainer = DragDropUtilities.GetItemContainer(this.sourceItemsControl, visual);
if (this.sourceItemContainer != null)
{
this.draggedData = this.sourceItemContainer.DataContext;
}
mouseDelta = e.GetPosition(sourceItemContainer);
}
private void DropTarget_PreviewDrop(object sender, DragEventArgs e)
{
if (isDragging)
{
object draggedItem = e.Data.GetData(this.format.Name);
int indexRemoved = -1;
if (draggedItem != null)
{
if (sourceItemsControl == targetItemsControl)
{
if ((e.Effects & DragDropEffects.Move) != 0)
{
indexRemoved = DragDropUtilities.RemoveItemFromItemsControl(this.sourceItemsControl,
draggedItem);
}
// This happens when we drag an item to a later position within the same ItemsControl.
if (indexRemoved != -1 && this.sourceItemsControl == this.targetItemsControl &&
indexRemoved < this.insertionIndex)
{
this.insertionIndex--;
}
DragDropUtilities.InsertItemInItemsControl(this.targetItemsControl, draggedItem,
this.insertionIndex);
}
else
{
if (draggedItem is ICloneable)
{
ICloneable cloneable = draggedItem as ICloneable;
DragDropUtilities.InsertItemInItemsControl(this.targetItemsControl, cloneable.Clone(),
this.insertionIndex);
}
else
{
DragDropUtilities.InsertItemInItemsControl(this.targetItemsControl, draggedItem,
this.insertionIndex);
}
}
RemoveDraggedAdorner();
RemoveInsertionAdorner();
}
e.Handled = true;
}
}
// If the types of the dragged data and ItemsControl's source are compatible,
// there are 3 situations to have into account when deciding the drop target:
// 1. mouse is over an items container
// 2. mouse is over the empty part of an ItemsControl, but ItemsControl is not empty
// 3. mouse is over an empty ItemsControl.
// The goal of this method is to decide on the values of the following properties:
// targetItemContainer, insertionIndex and isInFirstHalf.
private void DecideDropTarget(DragEventArgs e)
{
int targetItemsControlCount = this.targetItemsControl.Items.Count;
object draggedItem = e.Data.GetData(this.format.Name);
if (IsDropDataTypeAllowed(draggedItem))
{
if (targetItemsControlCount > 0)
{
this.hasVerticalOrientation = DragDropUtilities.HasVerticalOrientation(this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(0) as FrameworkElement);
this.targetItemContainer = DragDropUtilities.GetItemContainer(this.targetItemsControl, e.OriginalSource as Visual);
if (this.targetItemContainer != null)
{
Point positionRelativeToItemContainer = e.GetPosition(this.targetItemContainer);
this.isInFirstHalf = DragDropUtilities.IsInFirstHalf(this.targetItemContainer, positionRelativeToItemContainer, this.hasVerticalOrientation);
this.insertionIndex = this.targetItemsControl.ItemContainerGenerator.IndexFromContainer(this.targetItemContainer);
if (!this.isInFirstHalf)
{
this.insertionIndex++;
}
}
else
{
this.targetItemContainer = this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(targetItemsControlCount - 1) as FrameworkElement;
this.isInFirstHalf = false;
this.insertionIndex = targetItemsControlCount;
}
}
else
{
this.targetItemContainer = null;
this.insertionIndex = 0;
}
}
else
{
this.targetItemContainer = null;
this.insertionIndex = -1;
e.Effects = DragDropEffects.None;
}
}
// Drag = mouse down + move by a certain amount
private void DragSource_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (this.draggedData != null && !isDragging)
{
// Only drag when user moved the mouse by a reasonable amount.
if (DragDropUtilities.IsMovementBigEnough(this.initialMousePosition, e.GetPosition(this.topWindow)))
{
isDragging = true;
DataObject data = new DataObject(this.format.Name, this.draggedData);
// Adding events to the window to make sure dragged adorner comes up when mouse is not over a drop target.
bool previousAllowDrop = this.topWindow.AllowDrop;
this.topWindow.AllowDrop = true;
this.topWindow.DragEnter += TopWindow_DragEnter;
this.topWindow.DragOver += TopWindow_DragOver;
this.topWindow.DragLeave += TopWindow_DragLeave;
DragDropEffects effects = System.Windows.DragDrop.DoDragDrop((DependencyObject)sender, data, DragDropEffects.Move);
isDragging = false;
// Without this call, there would be a bug in the following scenario: Click on a data item, and drag
// the mouse very fast outside of the window. When doing this really fast, for some reason I don't get
// the Window leave event, and the dragged adorner is left behind.
// With this call, the dragged adorner will disappear when we release the mouse outside of the window,
// which is when the DoDragDrop synchronous method returns.
RemoveDraggedAdorner();
this.topWindow.AllowDrop = previousAllowDrop;
this.topWindow.DragEnter -= TopWindow_DragEnter;
this.topWindow.DragOver -= TopWindow_DragOver;
this.topWindow.DragLeave -= TopWindow_DragLeave;
this.draggedData = null;
}
}
}