'宣言
Protected Overridable Function RenderItem
(Of T2 As ComboEditorItemBase(Of TControl2),
TControl2 As FrameworkElement)( _
ByVal comboEditorItem As T2, _
ByVal availableSize As Size _
) As Size
protected virtual Size RenderItem<T2,TControl2>( T2 comboEditorItem, Size availableSize ) where T2: ComboEditorItemBase<TControl2> where TControl2: FrameworkElement