private void DisposeMementos()
{
if (_mementoRibbonBack1 != null)
{
_mementoRibbonBack1.Dispose();
_mementoRibbonBack1 = null;
}
if (_mementoRibbonBack2 != null)
{
_mementoRibbonBack2.Dispose();
_mementoRibbonBack2 = null;
}
if (_mementoStandardBack != null)
{
_mementoStandardBack.Dispose();
_mementoStandardBack = null;
}
}