public void SellAtMarket(string symbol, double volume)
 {
     Order order = new Order() { OrderType = OrderType.Sell, Volume = volume, IsMarket = true, Time = TestContext.CurrentTime };
     Orders.Add(order);
 }
 public void Sell(string symbol, double price, double volume)
 {
     Order order = new Order() { OrderType = OrderType.Sell, Price = price, Volume = volume, Time = TestContext.CurrentTime };
     Orders.Add(order);
 }