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;
}
//------------------------------------------------------
//
// 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);
}
}
}