internal void ClearItemContainer(object item, ItemsControl parentItemsControl)
{
if (VirtualizingPanel.GetIsVirtualizing(parentItemsControl))
{
//
// ItemValueStorage: save off values for this container if we're a virtualizing TreeView.
//
//
// Right now we have a hard-coded list of DPs we want to save off. In the future we could provide a 'register' API
// so that each ItemsControl could decide what DPs to save on its containers. Maybe we define a virtual method to
// retrieve a list of DPs the type is interested in. Alternatively we could have the contract
// be that ItemsControls use the ItemStorageService inside their ClearContainerForItemOverride by calling into StoreItemValues.
//
Helper.StoreItemValues(parentItemsControl, this, item);
// Tell the panel to clear off all its containers. This will cause this method to be called
// recursively down the tree, allowing all descendent data to be stored before we save off
// the ItemValueStorage DP for this container.
VirtualizingPanel vp = ItemsHost as VirtualizingPanel;
if (vp != null)
{
vp.OnClearChildrenInternal();
}
ItemContainerGenerator.RemoveAllInternal(true /*saveRecycleQueue*/);
}
// this container is going away - forget about its selection
ContainsSelection = false;
}
// Token: 0x06005A24 RID: 23076 RVA: 0x0018D68C File Offset: 0x0018B88C
internal static void OnVirtualizationPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ItemsControl itemsControl = d as ItemsControl;
if (itemsControl != null)
{
Panel itemsHost = itemsControl.ItemsHost;
if (itemsHost != null)
{
itemsHost.InvalidateMeasure();
ItemsPresenter itemsPresenter = VisualTreeHelper.GetParent(itemsHost) as ItemsPresenter;
if (itemsPresenter != null)
{
itemsPresenter.InvalidateMeasure();
}
if (d is TreeView)
{
DependencyProperty property = e.Property;
if (property == VirtualizingStackPanel.IsVirtualizingProperty || property == VirtualizingPanel.IsVirtualizingWhenGroupingProperty || property == VirtualizingStackPanel.VirtualizationModeProperty || property == VirtualizingPanel.ScrollUnitProperty)
{
VirtualizingPanel.VirtualizationPropertyChangePropagationRecursive(itemsControl, itemsHost);
}
}
}
}
}
// Token: 0x06004E0F RID: 19983 RVA: 0x0015FE30 File Offset: 0x0015E030
internal void ClearItemContainer(object item, ItemsControl parentItemsControl)
{
if (this.Generator == null)
{
return;
}
if (parentItemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(parentItemsControl))
{
Helper.StoreItemValues(parentItemsControl, this, item);
if (this._expander != null)
{
Helper.StoreItemValues(parentItemsControl, this._expander, item);
}
VirtualizingPanel virtualizingPanel = this._itemsHost as VirtualizingPanel;
if (virtualizingPanel != null)
{
virtualizingPanel.OnClearChildrenInternal();
}
this.Generator.RemoveAllInternal(true);
}
else
{
this.Generator.Release();
}
base.ClearContentControl(item);
}
/// <summary>
/// Recursively & syncronously expand all the nodes in this subtree.
/// </summary>
private static void ExpandRecursive(TreeViewItem item)
{
if (item == null)
{
return;
}
// Expand the current item
if (!item.IsExpanded)
{
item.SetCurrentValueInternal(IsExpandedProperty, BooleanBoxes.TrueBox);
}
// ApplyTemplate in order to generate the ItemsPresenter and the ItemsPanel. Note that in the
// virtualizing case even if the item is marked expanded we still need to do this step in order to
// regenerate the visuals because they may have been virtualized away.
item.ApplyTemplate();
ItemsPresenter itemsPresenter = (ItemsPresenter)item.Template.FindName(ItemsHostPartName, item);
if (itemsPresenter != null)
{
itemsPresenter.ApplyTemplate();
}
else
{
item.UpdateLayout();
}
VirtualizingPanel virtualizingPanel = item.ItemsHost as VirtualizingPanel;
item.ItemsHost.EnsureGenerator();
for (int i = 0, count = item.Items.Count; i < count; i++)
{
TreeViewItem subitem;
if (virtualizingPanel != null)
{
// We need to bring the item into view so that the container will be generated.
virtualizingPanel.BringIndexIntoView(i);
subitem = (TreeViewItem)item.ItemContainerGenerator.ContainerFromIndex(i);
}
else
{
subitem = (TreeViewItem)item.ItemContainerGenerator.ContainerFromIndex(i);
// We dont actually need to bring this into view, but we'll do it
// anyways to maintain the same behavior as with a virtualizing panel.
subitem.BringIntoView();
}
if (subitem != null)
{
ExpandRecursive(subitem);
}
}
}
// Token: 0x0600592F RID: 22831 RVA: 0x0018A4C1 File Offset: 0x001886C1
internal void PrepareItemContainer(object item, ItemsControl parentItemsControl)
{
Helper.ClearVirtualizingElement(this);
TreeViewItem.IsVirtualizingPropagationHelper(parentItemsControl, this);
if (VirtualizingPanel.GetIsVirtualizing(parentItemsControl))
{
Helper.SetItemValuesOnContainer(parentItemsControl, this, item);
}
}
//------------------------------------------------------
//
// Private Methods
//
//------------------------------------------------------
// initialize (called during measure, from ApplyTemplate)
void AttachToOwner()
{
DependencyObject templatedParent = this.TemplatedParent;
ItemsControl owner = templatedParent as ItemsControl;
ItemContainerGenerator generator;
if (owner != null)
{
// top-level presenter - get information from ItemsControl
generator = owner.ItemContainerGenerator;
}
else
{
// subgroup presenter - get information from GroupItem
GroupItem parentGI = templatedParent as GroupItem;
ItemsPresenter parentIP = FromGroupItem(parentGI);
if (parentIP != null)
{
owner = parentIP.Owner;
}
generator = (parentGI != null) ? parentGI.Generator : null;
}
_owner = owner;
UseGenerator(generator);
// create the panel, based either on ItemsControl.ItemsPanel or GroupStyle.Panel
ItemsPanelTemplate template = null;
GroupStyle groupStyle = (_generator != null) ? _generator.GroupStyle : null;
if (groupStyle != null)
{
// If GroupStyle.Panel is set then we dont honor ItemsControl.IsVirtualizing
template = groupStyle.Panel;
if (template == null)
{
// create default Panels
if (VirtualizingPanel.GetIsVirtualizingWhenGrouping(owner))
{
template = GroupStyle.DefaultVirtualizingStackPanel;
}
else
{
template = GroupStyle.DefaultStackPanel;
}
}
}
else
{
// Its a leaf-level ItemsPresenter, therefore pick ItemsControl.ItemsPanel
template = (_owner != null) ? _owner.ItemsPanel : null;
}
Template = template;
}
internal void ClearItemContainer(object item, ItemsControl parentItemsControl)
{
if (Generator == null)
{
return; // user-declared GroupItem - ignore (bug 108423)
}
ItemContainerGenerator generator = Generator.Parent;
GroupStyle groupStyle = generator.GroupStyle;
if (Object.Equals(this.Content, item))
{
ClearValue(ContentProperty);
}
if (this.ContentTemplate == groupStyle.HeaderTemplate)
{
ClearValue(ContentTemplateProperty);
}
if (this.ContentTemplateSelector == groupStyle.HeaderTemplateSelector)
{
ClearValue(ContentTemplateSelectorProperty);
}
if (this.ContentStringFormat == groupStyle.HeaderStringFormat)
{
ClearValue(ContentStringFormatProperty);
}
//
// ItemValueStorage: save off values for this container if we're a virtualizing Group.
//
if (parentItemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(parentItemsControl))
{
Helper.StoreItemValues((IContainItemStorage)parentItemsControl, this, item);
if (_expander != null)
{
Helper.StoreItemValues((IContainItemStorage)parentItemsControl, _expander, item);
}
// Tell the panel to clear off all its containers. This will cause this method to be called
// recursively down the tree, allowing all descendent data to be stored before we save off
// the ItemValueStorage DP for this container.
VirtualizingPanel vp = _itemsHost as VirtualizingPanel;
if (vp != null)
{
vp.OnClearChildrenInternal();
}
Generator.RemoveAllInternal(true /*saveRecycleQueue*/);
}
else
{
Generator.Release();
}
}
// Token: 0x06005930 RID: 22832 RVA: 0x0018A4E0 File Offset: 0x001886E0
internal void ClearItemContainer(object item, ItemsControl parentItemsControl)
{
if (VirtualizingPanel.GetIsVirtualizing(parentItemsControl))
{
Helper.StoreItemValues(parentItemsControl, this, item);
VirtualizingPanel virtualizingPanel = base.ItemsHost as VirtualizingPanel;
if (virtualizingPanel != null)
{
virtualizingPanel.OnClearChildrenInternal();
}
base.ItemContainerGenerator.RemoveAllInternal(true);
}
this.ContainsSelection = false;
}
/// <summary>Builds the visual tree for the <see cref="T:System.Windows.Controls.GroupItem" /> when a new template is applied. </summary>
// Token: 0x06004E07 RID: 19975 RVA: 0x0015FB34 File Offset: 0x0015DD34
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
this._header = (base.GetTemplateChild("PART_Header") as FrameworkElement);
this._expander = Helper.FindTemplatedDescendant<Expander>(this, this);
if (this._expander != null)
{
ItemsControl parentItemsControl = this.ParentItemsControl;
if (parentItemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(parentItemsControl))
{
Helper.SetItemValuesOnContainer(parentItemsControl, this._expander, parentItemsControl.ItemContainerGenerator.ItemFromContainer(this));
}
this._expander.Expanded += GroupItem.OnExpanded;
}
}
// Token: 0x06005934 RID: 22836 RVA: 0x0018A638 File Offset: 0x00188838
private static void ExpandRecursive(TreeViewItem item)
{
if (item == null)
{
return;
}
if (!item.IsExpanded)
{
item.SetCurrentValueInternal(TreeViewItem.IsExpandedProperty, BooleanBoxes.TrueBox);
}
item.ApplyTemplate();
ItemsPresenter itemsPresenter = (ItemsPresenter)item.Template.FindName("ItemsHost", item);
if (itemsPresenter != null)
{
itemsPresenter.ApplyTemplate();
}
else
{
item.UpdateLayout();
}
VirtualizingPanel virtualizingPanel = item.ItemsHost as VirtualizingPanel;
item.ItemsHost.EnsureGenerator();
int i = 0;
int count = item.Items.Count;
while (i < count)
{
TreeViewItem treeViewItem;
if (virtualizingPanel != null)
{
virtualizingPanel.BringIndexIntoView(i);
treeViewItem = (TreeViewItem)item.ItemContainerGenerator.ContainerFromIndex(i);
}
else
{
treeViewItem = (TreeViewItem)item.ItemContainerGenerator.ContainerFromIndex(i);
treeViewItem.BringIntoView();
}
if (treeViewItem != null)
{
TreeViewItem.ExpandRecursive(treeViewItem);
}
i++;
}
}
internal void PrepareItemContainer(object item, ItemsControl parentItemsControl)
{
//
// Clear previously cached items sizes
//
Helper.ClearVirtualizingElement((IHierarchicalVirtualizationAndScrollInfo)this);
IsVirtualizingPropagationHelper(parentItemsControl, this);
//
// ItemValueStorage: restore saved values for this item onto the new container
//
if (VirtualizingPanel.GetIsVirtualizing(parentItemsControl))
{
Helper.SetItemValuesOnContainer(parentItemsControl, this, item);
}
}
// Token: 0x06004E08 RID: 19976 RVA: 0x0015FBB4 File Offset: 0x0015DDB4
private static void OnExpanded(object sender, RoutedEventArgs e)
{
GroupItem groupItem = sender as GroupItem;
if (groupItem != null && groupItem._expander != null && groupItem._expander.IsExpanded)
{
ItemsControl parentItemsControl = groupItem.ParentItemsControl;
if (parentItemsControl != null && VirtualizingPanel.GetIsVirtualizing(parentItemsControl) && VirtualizingPanel.GetVirtualizationMode(parentItemsControl) == VirtualizationMode.Recycling)
{
ItemsPresenter itemsHostPresenter = groupItem.ItemsHostPresenter;
if (itemsHostPresenter != null)
{
groupItem.InvalidateMeasure();
Helper.InvalidateMeasureOnPath(itemsHostPresenter, groupItem, false);
}
}
}
}
// Token: 0x0600510F RID: 20751 RVA: 0x0016BAE4 File Offset: 0x00169CE4
private void AttachToOwner()
{
DependencyObject templatedParent = base.TemplatedParent;
ItemsControl itemsControl = templatedParent as ItemsControl;
ItemContainerGenerator generator;
if (itemsControl != null)
{
generator = itemsControl.ItemContainerGenerator;
}
else
{
GroupItem groupItem = templatedParent as GroupItem;
ItemsPresenter itemsPresenter = ItemsPresenter.FromGroupItem(groupItem);
if (itemsPresenter != null)
{
itemsControl = itemsPresenter.Owner;
}
generator = ((groupItem != null) ? groupItem.Generator : null);
}
this._owner = itemsControl;
this.UseGenerator(generator);
GroupStyle groupStyle = (this._generator != null) ? this._generator.GroupStyle : null;
ItemsPanelTemplate itemsPanelTemplate;
if (groupStyle != null)
{
itemsPanelTemplate = groupStyle.Panel;
if (itemsPanelTemplate == null)
{
if (VirtualizingPanel.GetIsVirtualizingWhenGrouping(itemsControl))
{
itemsPanelTemplate = GroupStyle.DefaultVirtualizingStackPanel;
}
else
{
itemsPanelTemplate = GroupStyle.DefaultStackPanel;
}
}
}
else
{
itemsPanelTemplate = ((this._owner != null) ? this._owner.ItemsPanel : null);
}
this.Template = itemsPanelTemplate;
}
// Token: 0x06005A25 RID: 23077 RVA: 0x0018D700 File Offset: 0x0018B900
private static void VirtualizationPropertyChangePropagationRecursive(DependencyObject parent, Panel itemsHost)
{
UIElementCollection internalChildren = itemsHost.InternalChildren;
int count = internalChildren.Count;
for (int i = 0; i < count; i++)
{
IHierarchicalVirtualizationAndScrollInfo hierarchicalVirtualizationAndScrollInfo = internalChildren[i] as IHierarchicalVirtualizationAndScrollInfo;
if (hierarchicalVirtualizationAndScrollInfo != null)
{
TreeViewItem.IsVirtualizingPropagationHelper(parent, (DependencyObject)hierarchicalVirtualizationAndScrollInfo);
Panel itemsHost2 = hierarchicalVirtualizationAndScrollInfo.ItemsHost;
if (itemsHost2 != null)
{
VirtualizingPanel.VirtualizationPropertyChangePropagationRecursive((DependencyObject)hierarchicalVirtualizationAndScrollInfo, itemsHost2);
}
}
}
}
private static void OnExpanded(object sender, RoutedEventArgs e)
{
GroupItem groupItem = sender as GroupItem;
if (groupItem != null && groupItem._expander != null && groupItem._expander.IsExpanded)
{
ItemsControl itemsControl = groupItem.ParentItemsControl;
if (itemsControl != null && VirtualizingPanel.GetIsVirtualizing(itemsControl) && VirtualizingPanel.GetVirtualizationMode(itemsControl) == VirtualizationMode.Recycling)
{
ItemsPresenter itemsHostPresenter = groupItem.ItemsHostPresenter;
if (itemsHostPresenter != null)
{
// In case a GroupItem that wasn't previously expanded is now
// recycled to represent an entity that is expanded, we face a situation
// where the ItemsHost isn't connected yet but we do need to synchronously
// remeasure the sub tree through the ItemsPresenter leading up to the
// ItemsHost panel. If we didnt do this the offsets could get skewed.
groupItem.InvalidateMeasure();
Helper.InvalidateMeasureOnPath(itemsHostPresenter, groupItem, false /*duringMeasure*/);
}
}
}
}
internal void ClearItemContainer(object item, ItemsControl parentItemsControl)
{
if (Generator == null)
{
return; // user-declared GroupItem - ignore (
}
//
// ItemValueStorage: save off values for this container if we're a virtualizing Group.
//
if (parentItemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(parentItemsControl))
{
Helper.StoreItemValues((IContainItemStorage)parentItemsControl, this, item);
if (_expander != null)
{
Helper.StoreItemValues((IContainItemStorage)parentItemsControl, _expander, item);
}
// Tell the panel to clear off all its containers. This will cause this method to be called
// recursively down the tree, allowing all descendent data to be stored before we save off
// the ItemValueStorage DP for this container.
VirtualizingPanel vp = _itemsHost as VirtualizingPanel;
if (vp != null)
{
vp.OnClearChildrenInternal();
}
Generator.RemoveAllInternal(true /*saveRecycleQueue*/);
}
else
{
Generator.Release();
}
ClearContentControl(item);
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
_header = this.GetTemplateChild("PART_Header") as FrameworkElement;
// GroupItem is generally re-templated to have an Expander.
// Look for an Expander and store its Header size.g
_expander = Helper.FindTemplatedDescendant <Expander>(this, this);
//
// ItemValueStorage: restore saved values for this item onto the new container
//
if (_expander != null)
{
ItemsControl itemsControl = ParentItemsControl;
if (itemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(itemsControl))
{
Helper.SetItemValuesOnContainer(itemsControl, _expander, itemsControl.ItemContainerGenerator.ItemFromContainer(this));
}
_expander.Expanded += new RoutedEventHandler(OnExpanded);
}
}
/// <summary>Adds the specified <see cref="T:System.Windows.UIElement" /> to the <see cref="P:System.Windows.Controls.Panel.InternalChildren" /> collection of a <see cref="T:System.Windows.Controls.VirtualizingPanel" /> element.</summary>
/// <param name="child">The <see cref="T:System.Windows.UIElement" /> child to add to the collection.</param>
// Token: 0x06005A28 RID: 23080 RVA: 0x0018D764 File Offset: 0x0018B964
protected void AddInternalChild(UIElement child)
{
VirtualizingPanel.AddInternalChild(base.InternalChildren, child);
}
/// <summary>Adds the specified <see cref="T:System.Windows.UIElement" /> to the <see cref="P:System.Windows.Controls.Panel.InternalChildren" /> collection of a <see cref="T:System.Windows.Controls.VirtualizingPanel" /> element at the specified index position.</summary>
/// <param name="index">The index position within the collection at which the child element is inserted.</param>
/// <param name="child">The <see cref="T:System.Windows.UIElement" /> child to add to the collection.</param>
// Token: 0x06005A29 RID: 23081 RVA: 0x0018D772 File Offset: 0x0018B972
protected void InsertInternalChild(int index, UIElement child)
{
VirtualizingPanel.InsertInternalChild(base.InternalChildren, index, child);
}
/// <summary>Removes child elements from the <see cref="P:System.Windows.Controls.Panel.InternalChildren" /> collection.</summary>
/// <param name="index">The beginning index position within the collection at which the first child element is removed.</param>
/// <param name="range">The total number of child elements to remove from the collection.</param>
// Token: 0x06005A2A RID: 23082 RVA: 0x0018D781 File Offset: 0x0018B981
protected void RemoveInternalChildRange(int index, int range)
{
VirtualizingPanel.RemoveInternalChildRange(base.InternalChildren, index, range);
}
// Token: 0x06005A23 RID: 23075 RVA: 0x0018D664 File Offset: 0x0018B864
private static object CoerceIsVirtualizingWhenGrouping(DependencyObject d, object baseValue)
{
bool isVirtualizing = VirtualizingPanel.GetIsVirtualizing(d);
return(isVirtualizing && (bool)baseValue);
}
// Token: 0x06004E0E RID: 19982 RVA: 0x0015FCB8 File Offset: 0x0015DEB8
internal void PrepareItemContainer(object item, ItemsControl parentItemsControl)
{
if (this.Generator == null)
{
return;
}
if (this._itemsHost != null)
{
this._itemsHost.IsItemsHost = true;
}
bool flag = parentItemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(parentItemsControl);
if (this.Generator != null)
{
if (!flag)
{
this.Generator.Release();
}
else
{
this.Generator.RemoveAllInternal(true);
}
}
ItemContainerGenerator parent = this.Generator.Parent;
GroupStyle groupStyle = parent.GroupStyle;
Style style = groupStyle.ContainerStyle;
if (style == null && groupStyle.ContainerStyleSelector != null)
{
style = groupStyle.ContainerStyleSelector.SelectStyle(item, this);
}
if (style != null)
{
if (!style.TargetType.IsInstanceOfType(this))
{
throw new InvalidOperationException(SR.Get("StyleForWrongType", new object[]
{
style.TargetType.Name,
base.GetType().Name
}));
}
base.Style = style;
base.WriteInternalFlag2(InternalFlags2.IsStyleSetFromGenerator, true);
}
if (base.ContentIsItem || !base.HasNonDefaultValue(ContentControl.ContentProperty))
{
base.Content = item;
base.ContentIsItem = true;
}
if (!base.HasNonDefaultValue(ContentControl.ContentTemplateProperty))
{
base.ContentTemplate = groupStyle.HeaderTemplate;
}
if (!base.HasNonDefaultValue(ContentControl.ContentTemplateSelectorProperty))
{
base.ContentTemplateSelector = groupStyle.HeaderTemplateSelector;
}
if (!base.HasNonDefaultValue(ContentControl.ContentStringFormatProperty))
{
base.ContentStringFormat = groupStyle.HeaderStringFormat;
}
Helper.ClearVirtualizingElement(this);
if (flag)
{
Helper.SetItemValuesOnContainer(parentItemsControl, this, item);
if (this._expander != null)
{
Helper.SetItemValuesOnContainer(parentItemsControl, this._expander, item);
}
}
}
private void ItemsControl_OnLoaded(object sender, RoutedEventArgs e)
{
_virtualizingPanel = UI.FindChild<VirtualizingStackPanel>(ItemsControl, "VirtualizingStackPanel");
}
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
internal void PrepareItemContainer(object item, ItemsControl parentItemsControl)
{
if (Generator == null)
{
return; // user-declared GroupItem - ignore (
}
// If a GroupItem is being recycled set back IsItemsHost
if (_itemsHost != null)
{
_itemsHost.IsItemsHost = true;
}
bool isVirtualizingWhenGrouping = (parentItemsControl != null && VirtualizingPanel.GetIsVirtualizingWhenGrouping(parentItemsControl));
// Release any previous containers. Also ensures Items and GroupStyle are hooked up correctly
if (Generator != null)
{
if (!isVirtualizingWhenGrouping)
{
Generator.Release();
}
else
{
Generator.RemoveAllInternal(true /*saveRecycleQueue*/);
}
}
ItemContainerGenerator generator = Generator.Parent;
GroupStyle groupStyle = generator.GroupStyle;
// apply the container style
Style style = groupStyle.ContainerStyle;
// no ContainerStyle set, try ContainerStyleSelector
if (style == null)
{
if (groupStyle.ContainerStyleSelector != null)
{
style = groupStyle.ContainerStyleSelector.SelectStyle(item, this);
}
}
// apply the style, if found
if (style != null)
{
// verify style is appropriate before applying it
if (!style.TargetType.IsInstanceOfType(this))
{
throw new InvalidOperationException(SR.Get(SRID.StyleForWrongType, style.TargetType.Name, this.GetType().Name));
}
this.Style = style;
this.WriteInternalFlag2(InternalFlags2.IsStyleSetFromGenerator, true);
}
// forward the header template information
if (ContentIsItem || !HasNonDefaultValue(ContentProperty))
{
this.Content = item;
ContentIsItem = true;
}
if (!HasNonDefaultValue(ContentTemplateProperty))
{
this.ContentTemplate = groupStyle.HeaderTemplate;
}
if (!HasNonDefaultValue(ContentTemplateSelectorProperty))
{
this.ContentTemplateSelector = groupStyle.HeaderTemplateSelector;
}
if (!HasNonDefaultValue(ContentStringFormatProperty))
{
this.ContentStringFormat = groupStyle.HeaderStringFormat;
}
//
// Clear previously cached items sizes
//
Helper.ClearVirtualizingElement(this);
//
// ItemValueStorage: restore saved values for this item onto the new container
//
if (isVirtualizingWhenGrouping)
{
Helper.SetItemValuesOnContainer(parentItemsControl, this, item);
if (_expander != null)
{
Helper.SetItemValuesOnContainer(parentItemsControl, _expander, item);
}
}
}
