protected override void UpdateContentCore() { base.UpdateContentCore(); DockTarget adornedElement = base.AdornedElement as DockTarget; if (adornedElement != null) { this.DockSiteType = adornedElement.DockSiteType; SplitterItem splitterItem = adornedElement.FindAncestor <SplitterItem>(); if (splitterItem != null) { this.IsFirst = SplitterPanel.GetIsFirst(splitterItem); this.IsLast = SplitterPanel.GetIsLast(splitterItem); } } }