void StartDragging()
{
try
{
using (ModelEditingScope editingScope = this.ModelItem.BeginEdit(SR.MoveEditingScopeDescription, true))
{
HashSet <WorkflowViewElement> draggedViews = new HashSet <WorkflowViewElement>();
Dictionary <ModelItem, ICompositeView> sourceContainers = new Dictionary <ModelItem, ICompositeView>();
HashSet <ICompositeView> compViewSet = new HashSet <ICompositeView>();
Selection selection = this.Context.Items.GetValue <Selection>();
IEnumerable <ModelItem> selectedObjects = selection.SelectedObjects;
IEnumerable <ModelItem> modelItemsToDrag = DragDropHelper.GetModelItemsToDrag(selectedObjects);
// Save the source containers for the dragged items
foreach (ModelItem modelItem in modelItemsToDrag)
{
WorkflowViewElement view = (WorkflowViewElement)modelItem.View;
draggedViews.Add(view);
ICompositeView container = DragDropHelper.GetCompositeView(view) as ICompositeView;
sourceContainers.Add(modelItem, container);
// If Add returns true => the container is added the first time, which is always ok
// If Add returns false => the container is added more than once
// it must be a IMultipleDragEnabledCompositeView, otherwise, return, because
// we don't support dragging from ICompositeView.
if (!compViewSet.Add(container) && !(container is IMultipleDragEnabledCompositeView))
{
return;
}
}
// Calculate the anchor point for the dragged items
Point relativeLocation = GetRelativeLocation(draggedViews);
Point referencePoint = this.lastMouseDownPoint;
referencePoint.Offset(relativeLocation.X, relativeLocation.Y);
DataObject dataObject = DragDropHelper.DoDragMoveImpl(draggedViews, referencePoint);
IEnumerable <WorkflowViewElement> movedViewElements = DragDropHelper.GetDragDropMovedViewElements(dataObject);
// once drag drop is done make sure the CompositeView is notified of the change in data
if (movedViewElements != null)
{
Dictionary <ICompositeView, List <ModelItem> > containerMovedModelItemList = new Dictionary <ICompositeView, List <ModelItem> >();
// Create containerMovedModelItemList
foreach (WorkflowViewElement view in movedViewElements)
{
ICompositeView compView = DragDropHelper.GetCompositeView(view) as ICompositeView;
Fx.Assert(compView != null, "not an ICompositeView");
if (!containerMovedModelItemList.ContainsKey(compView))
{
containerMovedModelItemList.Add(compView, new List <ModelItem>());
}
containerMovedModelItemList[compView].Add(view.ModelItem);
}
// Call OnItemsMoved to notify the source container.
foreach (KeyValuePair <ICompositeView, List <ModelItem> > pair in containerMovedModelItemList)
{
if (pair.Key is IMultipleDragEnabledCompositeView)
{
((IMultipleDragEnabledCompositeView)pair.Key).OnItemsMoved(pair.Value);
}
else
{
if (pair.Value.Count >= 2)
{
throw FxTrace.Exception.AsError(
new InvalidOperationException(SR.Error_MovingMoreThanOneItemsFromICompositeView));
}
pair.Key.OnItemMoved(pair.Value[0]);
}
}
// animation
foreach (WorkflowViewElement view in movedViewElements)
{
BeginDropAnimation(view);
}
}
// the drop target is using old DragDropHelper API and did not set the moved view elements
else
{
DragDropEffects executedDragDropEffect = DragDropHelper.GetDragDropCompletedEffects(dataObject);
if (executedDragDropEffect == DragDropEffects.Move)
{
if (modelItemsToDrag.Count() == 1)
{
ModelItem movedItem = modelItemsToDrag.First <ModelItem>();
sourceContainers[movedItem].OnItemMoved(movedItem);
BeginDropAnimation((WorkflowViewElement)movedItem.View);
}
else
{
throw FxTrace.Exception.AsError(new InvalidOperationException(SR.DraggingMulitpleItemsError));
}
}
}
editingScope.Complete();
bool dropHappened = movedViewElements != null ||
DragDropHelper.GetDragDropCompletedEffects(dataObject) == DragDropEffects.Move;
if (dropHappened)
{
// add the selected objects back into selection.
this.Dispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, (Action)(() =>
{
foreach (ModelItem item in selectedObjects)
{
// We need only the first one
IInputElement viewToFocus = item == null ? null : item.View as IInputElement;
if (viewToFocus != null)
{
Keyboard.Focus(viewToFocus);
break;
}
}
this.Context.Items.SetValue(new Selection(selectedObjects));
}));
}
}
}
catch (Exception e)
{
ErrorReporting.ShowErrorMessage(e.Message);
}
}