protected override SizeF ArrangeOverride(SizeF arrangeSize)
        {
            SizeF sizeF = base.ArrangeOverride(arrangeSize);
            RadCollapsiblePanelElement parent = this.Parent as RadCollapsiblePanelElement;
            RadDirection expandDirection      = parent != null ? parent.ExpandDirection : RadDirection.Down;

            if (this.Orientation == Orientation.Horizontal)
            {
                this.ArrangeAccordingToHorizontalHeaderAlignment(arrangeSize);
            }
            else
            {
                this.ArrangeAccordingToVerticalHeaderAlignment(arrangeSize);
            }
            this.ArrangeLineInMiddle(expandDirection, arrangeSize);
            return(sizeF);
        }
 protected override void CreateChildItems(RadElement parent)
 {
     this.collapsiblePanelElement = this.CreateCollapsiblePanelElement();
     parent.Children.Add((RadElement)this.collapsiblePanelElement);
 }