private void DragSourceManager_DragOutsideQueryCursor(object sender, QueryCursorEventArgs e)
{
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(this);
if ((hierarchicalGroupByControlNode == null) ||
(!hierarchicalGroupByControlNode.IsGroupingModificationAllowed))
{
return;
}
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
if ((dataGridContext != null) && (dataGridContext.DataGridControl != null))
{
UIViewBase uiViewBase = dataGridContext.DataGridControl.GetView() as UIViewBase;
e.Cursor = (uiViewBase != null)
? uiViewBase.RemovingGroupCursor
: UIViewBase.DefaultGroupDraggedOutsideCursor;
}
else
{
e.Cursor = UIViewBase.DefaultGroupDraggedOutsideCursor;
}
}
internal void ShowFarDropMark(Point mousePosition)
{
int itemsCount = this.Items.Count;
if (itemsCount < 1)
{
if (m_dropMarkAdorner == null)
{
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
DataGridControl grid = (dataGridContext != null)
? dataGridContext.DataGridControl
: null;
Pen pen = UIViewBase.GetDropMarkPen(this);
if ((pen == null) && (grid != null))
{
UIViewBase uiViewBase = grid.GetView() as UIViewBase;
pen = uiViewBase.DefaultDropMarkPen;
}
DropMarkOrientation orientation = UIViewBase.GetDropMarkOrientation(this);
if ((orientation == DropMarkOrientation.Default) && (grid != null))
{
UIViewBase uiViewBase = grid.GetView() as UIViewBase;
orientation = uiViewBase.DefaultDropMarkOrientation;
}
m_dropMarkAdorner = new DropMarkAdorner(this, pen, orientation);
AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this);
if (adornerLayer != null)
{
adornerLayer.Add(m_dropMarkAdorner);
}
}
// We Only want the drop mark to be displayed at the end of the HierarchicalGroupByControlNode
m_dropMarkAdorner.ForceAlignment(DropMarkAlignment.Far);
}
else
{
HierarchicalGroupByItem hierarchicalGroupByItem = this.ItemContainerGenerator.ContainerFromIndex(itemsCount - 1) as HierarchicalGroupByItem;
Debug.Assert(hierarchicalGroupByItem != null);
GroupLevelDescription groupLevelDescription = hierarchicalGroupByItem.Content as GroupLevelDescription;
Debug.Assert(groupLevelDescription != null);
// Show Far DropMark only if not already grouped
if (this.Items.Contains(groupLevelDescription) == false)
{
hierarchicalGroupByItem.ShowFarDropMark(mousePosition);
}
}
}
internal HierarchicalGroupByItemToggleColumnSortCommand(HierarchicalGroupByItem target)
: base()
{
if (target == null)
{
throw new ArgumentNullException("owner");
}
m_target = new WeakReference(target);
if (target.ParentDataGridContext != null)
{
m_dataGridContext = new WeakReference(target.ParentDataGridContext);
}
DataGridContext groupByItemDataGridContext = DataGridControl.GetDataGridContext(target);
ToggleColumnSortCommand.ThrowIfNull(groupByItemDataGridContext, "groupByItemDataGridContext");
DataGridControl dataGridControl = groupByItemDataGridContext.DataGridControl;
ToggleColumnSortCommand.ThrowIfNull(dataGridControl, "dataGridControl");
m_dataGridControl = new WeakReference(dataGridControl);
}
void IDropTarget.DragLeave(UIElement draggedElement)
{
ColumnManagerCell cell = draggedElement as ColumnManagerCell;
if (cell != null)
{
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = this.GetHierarchicalGroupByControlNodeFromColumnManagerCell(cell);
// It may not be visible
if (hierarchicalGroupByControlNode != null)
{
hierarchicalGroupByControlNode.HideFarDropMark();
}
}
else
{
HierarchicalGroupByItem hierarchicalGroupByItem = draggedElement as HierarchicalGroupByItem;
if (hierarchicalGroupByItem == null)
{
return;
}
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = this.GetHierarchicalGroupByControlNodeFromHierarchicalGroupByItem(hierarchicalGroupByItem);
Debug.Assert(hierarchicalGroupByControlNode != null, "CanDrop should have returned false");
if (hierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("A HierarchicalGroupByControlNode must exist for every level.");
}
hierarchicalGroupByControlNode.HideFarDropMark();
}
}
internal void ShowFarDropMark(ColumnManagerCell cell, Point mousePosition)
{
Debug.Assert(cell != null);
if (cell == null)
{
return;
}
DataGridContext cellDataGridContext = DataGridControl.GetDataGridContext(cell);
Debug.Assert(cellDataGridContext != null);
if (cellDataGridContext == null)
{
throw new DataGridInternalException("DataGridContext cannot be null on ColumnManagerCell.");
}
// We already have GroupLevelDescriptions for this level, we should show DropMark on the last HierarchicalGroupByItem
if (cellDataGridContext.GroupLevelDescriptions.Count > 0)
{
Debug.Assert(cellDataGridContext.GroupLevelDescriptions == this.GroupLevelDescriptions);
if (cellDataGridContext.GroupLevelDescriptions != this.GroupLevelDescriptions)
{
return;
}
int lastIndex = this.GroupLevelDescriptions.Count - 1;
// If there
if (lastIndex > -1)
{
HierarchicalGroupByItem hierarchicalGroupByItem = this.ItemContainerGenerator.ContainerFromItem(this.GroupLevelDescriptions[lastIndex]) as HierarchicalGroupByItem;
Debug.Assert(hierarchicalGroupByItem != null);
if (hierarchicalGroupByItem == null)
{
return;
}
hierarchicalGroupByItem.ShowFarDropMark(mousePosition);
}
else
{
this.ShowFarDropMark(mousePosition);
}
}
else
{
this.ShowFarDropMark(mousePosition);
}
}
protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
{
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
DataGridControl grid = (dataGridContext != null)
? dataGridContext.DataGridControl
: null;
base.PrepareContainerForItemOverride(element, item);
if (grid != null)
{
HierarchicalGroupByItem groupByItem = ( HierarchicalGroupByItem )element;
groupByItem.PrepareDefaultStyleKey(grid.GetView());
}
}
private void DragSourceManager_DroppedOutside(object sender, EventArgs e)
{
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(this);
if (hierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("hierarchicalGroupByControlNode is null.");
}
bool allowGroupingModification = hierarchicalGroupByControlNode.IsGroupingModificationAllowed;
if (!allowGroupingModification)
{
return;
}
ObservableCollection <GroupDescription> groupDescriptions = this.ParentGroupDescriptions;
if (groupDescriptions != null)
{
// Get the HierarchicalGroupByControl before removing us from it
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(this);
GroupLevelDescription groupLevelDescription = this.Content as GroupLevelDescription;
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
DataGridControl parentDataGridControl = (dataGridContext != null)
? dataGridContext.DataGridControl
: null;
GroupingHelper.RemoveGroupDescription(groupDescriptions, groupLevelDescription, parentDataGridControl);
// Notify groups have changed for NoGroupContent
parentGBC.UpdateHasGroups();
// Update the HasGroups property
Debug.Assert(parentGBC != null);
if (parentGBC == null)
{
throw new DataGridInternalException("The hierarchical group-by item must be rooted by a HierarchicalGroupByControl.");
}
}
}
internal void HideFarDropMark()
{
int itemsCount = this.Items.Count;
if (itemsCount > 0)
{
HierarchicalGroupByItem hierarchicalGroupByItem = null;
if (itemsCount > 1)
{
// Hide the before last item's DropMark if any in case
hierarchicalGroupByItem = this.ItemContainerGenerator.ContainerFromIndex(itemsCount - 2) as HierarchicalGroupByItem;
Debug.Assert(hierarchicalGroupByItem != null);
if (hierarchicalGroupByItem != null)
{
hierarchicalGroupByItem.HideDropMark();
}
}
// Hide last item's DropMark if any
hierarchicalGroupByItem = this.ItemContainerGenerator.ContainerFromIndex(itemsCount - 1) as HierarchicalGroupByItem;
Debug.Assert(hierarchicalGroupByItem != null);
if (hierarchicalGroupByItem != null)
{
hierarchicalGroupByItem.HideDropMark();
}
}
if (m_dropMarkAdorner != null)
{
AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this);
if (adornerLayer != null)
{
adornerLayer.Remove(m_dropMarkAdorner);
}
m_dropMarkAdorner = null;
}
}
void IDropTarget.Drop(UIElement draggedElement)
{
ColumnManagerCell draggedColumnManagerCell = draggedElement as ColumnManagerCell;
if (m_dropMarkAdorner != null)
{
GroupLevelDescription draggedOverGroupLevelDescription = this.Content as GroupLevelDescription;
DropMarkAlignment alignment = m_dropMarkAdorner.Alignment;
this.HideDropMark();
if (draggedColumnManagerCell != null)
{
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
DataGridControl parentGrid = (dataGridContext != null)
? dataGridContext.DataGridControl
: null;
GroupingHelper.AddNewGroupFromColumnManagerCell(draggedColumnManagerCell, draggedOverGroupLevelDescription, alignment, parentGrid);
}
else
{
HierarchicalGroupByItem draggedGroupByItem = draggedElement as HierarchicalGroupByItem;
if (draggedGroupByItem == null)
{
return;
}
GroupLevelDescription draggedGroupLevelDescription = draggedGroupByItem.Content as GroupLevelDescription;
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
DataGridControl parentDataGridControl = (dataGridContext != null)
? dataGridContext.DataGridControl
: null;
GroupLevelDescription destinationGroupLevelDescription = this.Content as GroupLevelDescription;
GroupingHelper.MoveGroupDescription(this.ParentColumns, this.ParentGroupDescriptions,
destinationGroupLevelDescription, alignment,
draggedGroupLevelDescription, parentDataGridControl);
}
}
else
{
// We try to add a new Group which is not in the current GroupLevelDescriptions
if (draggedColumnManagerCell == null)
{
return;
}
DataGridContext dataGridContext = DataGridControl.GetDataGridContext(this);
DataGridControl parentGrid = (dataGridContext != null)
? dataGridContext.DataGridControl
: null;
GroupingHelper.AppendNewGroupFromColumnManagerCell(draggedColumnManagerCell, parentGrid);
}
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(this);
Debug.Assert(parentGBC != null);
if (parentGBC == null)
{
throw new DataGridInternalException("A hierarchical group-by item must be rooted by a HierarchicalGroupByControl.");
}
// Notify groups have changed for NoGroupContent
parentGBC.UpdateHasGroups();
}
void IDropTarget.DragLeave(UIElement draggedElement)
{
ColumnManagerCell cell = draggedElement as ColumnManagerCell;
if (cell != null)
{
DataGridContext draggedCellDataGridContext = DataGridControl.GetDataGridContext(cell);
HierarchicalGroupByControlNode draggedOverHierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(this);
if (draggedOverHierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("We should never be dragged over and not contained inside a HierarchicalGroupByControlNode.");
}
if (draggedOverHierarchicalGroupByControlNode.GroupLevelDescriptions == draggedCellDataGridContext.GroupLevelDescriptions)
{
this.HideDropMark();
}
else
{
// This ColumnManagerCell does not belong this parent HierarchicalGroupByControlNode, display the DropMark on the correct one
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(draggedOverHierarchicalGroupByControlNode);
if (parentGBC == null)
{
throw new DataGridInternalException("A hierarchical group-by item must be rooted by a HierarchicalGroupByControl.");
}
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = parentGBC.GetHierarchicalGroupByControlNodeFromColumnManagerCell(cell);
Debug.Assert(hierarchicalGroupByControlNode != null, "CanDrop should have returned false");
if (hierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("A HierarchicalGroupByControlNode must exist for every level.");
}
hierarchicalGroupByControlNode.HideFarDropMark(cell);
}
}
else
{
HierarchicalGroupByItem hierarchicalGroupByItem = draggedElement as HierarchicalGroupByItem;
if (hierarchicalGroupByItem == null)
{
return;
}
HierarchicalGroupByControlNode draggedHierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(hierarchicalGroupByItem);
HierarchicalGroupByControlNode draggedOverHierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(this);
if (draggedHierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("draggedHierarchicalGroupByControlNode is null.");
}
if (draggedOverHierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("draggedOverHierarchicalGroupByControlNode is null.");
}
if (draggedHierarchicalGroupByControlNode.GroupLevelDescriptions == draggedOverHierarchicalGroupByControlNode.GroupLevelDescriptions)
{
this.HideDropMark();
}
else
{
// This HierarchicalGroupByItem does not belong this parent HierarchicalGroupByControlNode, display the DropMark on the correct one
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(draggedOverHierarchicalGroupByControlNode);
Debug.Assert(parentGBC != null);
if (parentGBC == null)
{
throw new DataGridInternalException("A hierarchical group-by item must be rooted by a HierarchicalGroupByControl.");
}
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = parentGBC.GetHierarchicalGroupByControlNodeFromHierarchicalGroupByItem(hierarchicalGroupByItem);
Debug.Assert(hierarchicalGroupByControlNode != null, "CanDrop should have returned false");
if (hierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("A HierarchicalGroupByControlNode must exist for every level.");
}
hierarchicalGroupByControlNode.HideFarDropMark();
}
}
}
bool IDropTarget.CanDropElement(UIElement draggedElement)
{
bool canDrop = true;
// Check if this HierarchicalGroupByItem parent HierarchicalGroupByControlNode allows grouping modifications, default yes
HierarchicalGroupByControlNode parentHierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(this);
if (parentHierarchicalGroupByControlNode != null)
{
canDrop = parentHierarchicalGroupByControlNode.IsGroupingModificationAllowed;
}
ColumnManagerCell cell = draggedElement as ColumnManagerCell;
HierarchicalGroupByItem hierarchicalGroupByItem = null;
if (canDrop)
{
if (cell != null)
{
ColumnBase parentColumn = cell.ParentColumn;
if ((parentColumn == null) || (!parentColumn.AllowGroup))
{
return(false);
}
// Check if already grouped using the cell's DataGridContext
canDrop = !GroupingHelper.IsAlreadyGroupedBy(cell);
if (canDrop)
{
// Get the HierarchicalGroupByControl for this HierarchicalGroupByItem
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(parentHierarchicalGroupByControlNode);
if (parentGBC == null)
{
throw new DataGridInternalException("The hierarchical group-by item must be rooted by a HierarchicalGroupByControl.");
}
DataGridContext parentGBCDataGridContext = DataGridControl.GetDataGridContext(parentGBC);
if (parentGBCDataGridContext.Items != null)
{
canDrop = parentGBCDataGridContext.Items.CanGroup;
}
if (canDrop)
{
canDrop = GroupingHelper.IsColumnManagerCellInDataGridContext(parentGBCDataGridContext, cell);
if (canDrop == true)
{
canDrop = GroupingHelper.ValidateMaxGroupDescriptions(DataGridControl.GetDataGridContext(draggedElement));
}
}
}
}
else
{
hierarchicalGroupByItem = draggedElement as HierarchicalGroupByItem;
if (hierarchicalGroupByItem == null)
{
canDrop = false;
}
if (canDrop)
{
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(parentHierarchicalGroupByControlNode);
if (parentGBC == null)
{
throw new DataGridInternalException("The hierarchical group-by item must be rooted by a HierarchicalGroupByControl.");
}
// Try to get the HierarchicalGroupByControlNode in which this HierarchicalGroupByItem can be added using the parent HierarchicalGroupByControl => null it can't
HierarchicalGroupByControlNode draggedHierarchicalGroupByControlNode = parentGBC.GetHierarchicalGroupByControlNodeFromHierarchicalGroupByItem(hierarchicalGroupByItem);
if (draggedHierarchicalGroupByControlNode == null)
{
canDrop = false;
}
}
}
}
bool returnedValue = ((cell != null) || (hierarchicalGroupByItem != null)) && // ColumnManagerCell or HierarchicalGroupByItem
(draggedElement != this) &&
(canDrop);
return(returnedValue);
}
private static void OnSortDirectionInternalChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
HierarchicalGroupByItem groupByItem = ( HierarchicalGroupByItem )sender;
groupByItem.OnPropertyChanged(new PropertyChangedEventArgs("SortDirection"));
}
void IDropTarget.DragOver(UIElement draggedElement, Point mousePosition)
{
ColumnManagerCell cell = draggedElement as ColumnManagerCell;
if (cell != null)
{
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(this);
if (parentGBC == null)
{
throw new DataGridInternalException("The hierarchical group-by control node must be rooted by a HierarchicalGroupByControl.");
}
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = parentGBC.GetHierarchicalGroupByControlNodeFromColumnManagerCell(cell);
if (hierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("A HierarchicalGroupByControlNode must exist for every level.");
}
hierarchicalGroupByControlNode.ShowFarDropMark(cell, mousePosition);
}
else
{
HierarchicalGroupByItem hierarchicalGroupByItem = draggedElement as HierarchicalGroupByItem;
if (hierarchicalGroupByItem == null)
{
return;
}
HierarchicalGroupByControlNode draggedHierarchicalGroupByControlNode = HierarchicalGroupByItem.GetParentHierarchicalGroupByControlNode(hierarchicalGroupByItem);
if (draggedHierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("draggedHierarchicalGroupByControlNode is null.");
}
if (draggedHierarchicalGroupByControlNode.GroupLevelDescriptions == this.GroupLevelDescriptions)
{
this.ShowFarDropMark(mousePosition);
}
else
{
// This HierarchicalGroupByItem does not belong this parent HierarchicalGroupByControlNode, display the DropMark on the correct one
HierarchicalGroupByControl parentGBC = GroupingHelper.GetHierarchicalGroupByControl(this);
if (parentGBC == null)
{
throw new DataGridInternalException("The hierarchical group-by control node must be rooted by a HierarchicalGroupByControl.");
}
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = parentGBC.GetHierarchicalGroupByControlNodeFromHierarchicalGroupByItem(hierarchicalGroupByItem);
Debug.Assert(hierarchicalGroupByControlNode != null, "CanDrop should have returned false");
if (hierarchicalGroupByControlNode == null)
{
throw new DataGridInternalException("A HierarchicalGroupByControlNode must exist for every level.");
}
hierarchicalGroupByControlNode.ShowFarDropMark(mousePosition);
}
}
}
bool IDropTarget.CanDropElement(UIElement draggedElement)
{
bool canDrop = this.AllowGroupingModification;
ColumnManagerCell cell = null;
HierarchicalGroupByItem hierarchicalGroupByItem = null;
if (canDrop)
{
cell = draggedElement as ColumnManagerCell;
if (cell != null)
{
ColumnBase parentColumn = cell.ParentColumn;
if ((parentColumn == null) || (!parentColumn.AllowGroup))
{
return(false);
}
// Check if already grouped using the cell's DataGridContext
canDrop = !GroupingHelper.IsAlreadyGroupedBy(cell);
if (canDrop)
{
DataGridContext thisDataGridContext = DataGridControl.GetDataGridContext(this);
if (thisDataGridContext.Items != null)
{
canDrop = thisDataGridContext.Items.CanGroup;
}
if (canDrop)
{
canDrop = GroupingHelper.IsColumnManagerCellInDataGridContext(thisDataGridContext, cell);
if (canDrop == true)
{
canDrop = GroupingHelper.ValidateMaxGroupDescriptions(DataGridControl.GetDataGridContext(draggedElement));
}
}
}
}
else
{
hierarchicalGroupByItem = draggedElement as HierarchicalGroupByItem;
if (hierarchicalGroupByItem == null)
{
canDrop = false;
}
if (canDrop)
{
// Try to get the HierarchicalGroupByControlNode in which this HierarchicalGroupByItem can be added using the parent HierarchicalGroupByControl => null it can't
HierarchicalGroupByControlNode draggedHierarchicalGroupByControlNode = this.GetHierarchicalGroupByControlNodeFromHierarchicalGroupByItem(hierarchicalGroupByItem);
if (draggedHierarchicalGroupByControlNode == null)
{
canDrop = false;
}
}
}
}
bool returnedValue = ((cell != null) || (hierarchicalGroupByItem != null)) && // ColumnManagerCell or HierarchicalGroupByItem
(canDrop);
return(returnedValue);
}
internal HierarchicalGroupByControlNode GetHierarchicalGroupByControlNodeFromHierarchicalGroupByItem(HierarchicalGroupByItem hierarchicalGroupByItem)
{
Debug.Assert(hierarchicalGroupByItem != null);
if (hierarchicalGroupByItem == null)
{
return(null);
}
TreeView treeView = this.GetTemplateChild(@"PART_HierarchicalGroupByControlTreeView") as TreeView;
if (treeView == null)
{
return(null);
}
if (treeView.Items.Count == 0)
{
throw new DataGridInternalException("The HierarchicalGroupByControl should contain at least one grouping level.");
}
// The first item is always the top level HierarchicalGroupByControlNode
TreeViewItem rootItem = treeView.ItemContainerGenerator.ContainerFromItem(treeView.Items[0]) as TreeViewItem;
if (rootItem == null)
{
throw new DataGridInternalException("The root item is null.");
}
GroupLevelDescription detailGroupLevelDescription = hierarchicalGroupByItem.Content as GroupLevelDescription;
Debug.Assert(detailGroupLevelDescription != null);
TreeViewItem dropMarkedTreeViewItem = null;
DataGridContext rootDataGridContext = rootItem.Header as DataGridContext;
Debug.Assert(rootDataGridContext != null);
if (rootDataGridContext.GroupLevelDescriptions.Contains(detailGroupLevelDescription))
{
dropMarkedTreeViewItem = rootItem;
}
else
{
dropMarkedTreeViewItem = HierarchicalGroupByControl.GetTreeViewItemFromGroupLevelDescription(rootItem, detailGroupLevelDescription);
}
// If null, it means the cell does not belong to this detail
if (dropMarkedTreeViewItem == null)
{
return(null);
}
ContentPresenter treeViewItemHeader = dropMarkedTreeViewItem.Template.FindName("PART_Header", dropMarkedTreeViewItem) as ContentPresenter;
Debug.Assert(treeViewItemHeader != null);
if (treeViewItemHeader == null)
{
throw new DataGridInternalException("An error occurred while retrieving the PART_Header template part of an item containing a HierarchicalGroupByControlNode.");
}
HierarchicalGroupByControlNode hierarchicalGroupByControlNode = HierarchicalGroupByControl.GetHierarchicalGroupByControlNode(treeViewItemHeader);
return(hierarchicalGroupByControlNode);
}