/// <summary>
/// Invoked when logical parent is changed. This just
/// sets the parent pointer.
/// </summary>
/// <remarks>
/// A parent change is considered catastrohpic and results in a large
/// amount of invalidations and tree traversals. <cref see="DependencyFastBuild"/>
/// is recommended to reduce the work necessary to build a tree
/// </remarks>
/// <param name="newParent">
/// New parent that was set
/// </param>
internal void ChangeLogicalParent(DependencyObject newParent)
{
///////////////////
// OnNewParent:
///////////////////
//
// -- Approved By The Core Team --
//
// Do not allow foreign threads to change the tree.
// (This is a noop if this object is not assigned to a Dispatcher.)
//
// We also need to ensure that the tree is homogenous with respect
// to the dispatchers that the elements belong to.
//
this.VerifyAccess();
if (newParent != null)
{
newParent.VerifyAccess();
}
// Logical Parent must first be dropped before you are attached to a newParent
// This mitigates illegal tree state caused by logical child stealing as illustrated in bug 970706
if (_parent != null && newParent != null && _parent != newParent)
{
throw new System.InvalidOperationException(SR.Get(SRID.HasLogicalParent));
}
// Trivial check to avoid loops
if (newParent == this)
{
throw new System.InvalidOperationException(SR.Get(SRID.CannotBeSelfParent));
}
// invalid during a VisualTreeChanged event
VisualDiagnostics.VerifyVisualTreeChange(this);
// Logical Parent implies no InheritanceContext
if (newParent != null)
{
ClearInheritanceContext();
}
IsParentAnFE = newParent is FrameworkElement;
DependencyObject oldParent = _parent;
OnNewParent(newParent);
// Update Has[Loaded/Unloaded]Handler Flags
BroadcastEventHelper.AddOrRemoveHasLoadedChangeHandlerFlag(this, oldParent, newParent);
// Fire Loaded and Unloaded Events
BroadcastEventHelper.BroadcastLoadedOrUnloadedEvent(this, oldParent, newParent);
///////////////////
// OnParentChanged:
///////////////////
// Invalidate relevant properties for this subtree
DependencyObject parent = (newParent != null) ? newParent : oldParent;
TreeWalkHelper.InvalidateOnTreeChange(/* fe = */ null, /* fce = */ this, parent, (newParent != null));
// If no one has called BeginInit then mark the element initialized and fire Initialized event
// (non-parser programmatic tree building scenario)
TryFireInitialized();
}