public void DeleteDessert(Dessert dessert) => MenuDesserts.Remove(MenuDesserts.SingleOrDefault(md => md.DessertId == dessert.Id));
public void AddDessert(Dessert dessert, DateTime datum) => MenuDesserts.Add(new MenuDessert()
{
MenuId = Id, Menu = this, DessertId = dessert.Id, Dessert = dessert, Datum = datum
});