public Trade(SalesPerson person, int quantity)
{
this.Person = person;
this.QuantitySold = quantity;
}
public void BuyStock(SalesPerson person, string item, int quantity)
{
_stock.AddOrUpdate(item, quantity, (key, oldvalue) => oldvalue + quantity);
Interlocked.Add(ref _totalQuantityBought, quantity);
_toDoQueue.AddTrade(new Trade(person, quantity));
}