public IEnumerable <StockItem> Handle(CheckStockAsAtDate checkStock)
{
return(_shop.StockList.OfType <Dress>()
.Select(dsi => dsi.AsAtDate(checkStock.StockCheckDate)));
}
public IEnumerable <TinnedFood> Handle(CheckStockAsAtDate checkStock)
{
return(_shop.StockList
.OfType <TinnedFood>()
.Where(dsi => dsi.IsSaleable(checkStock.StockCheckDate)));
}