private async Task LoadStocksFromStocksService()
{
try
{
var service = new StocksService();
var data = await service.GetStockPricesFor(Ticker.Text, cancellationTokenSource.Token);
Stocks.ItemsSource = data;
}
catch (Exception ex)
{
Notes.Text += ex.InnerException.Message + Environment.NewLine;
}
}
private async Task ProcessStocksOnArrival()
{
try
{
var tickers = Ticker.Text.Split(',', ' ');
var service = new StocksService();
var stocks = new ConcurrentBag <StockPrice>();
var tickerLoadingTasks = new List <Task <IEnumerable <StockPrice> > >();
foreach (var ticker in tickers)
{
var loadtask = service.GetStockPricesFor(ticker, cancellationTokenSource.Token)
.ContinueWith(t =>
{
foreach (var stock in t.Result.Take(5))
{
// stocks collection can be safely used with different threads
stocks.Add(stock);
}
Dispatcher.Invoke(() =>
{
Stocks.ItemsSource = stocks.ToArray();
});
return(t.Result);
});
tickerLoadingTasks.Add(loadtask);
}
await Task.WhenAll(tickerLoadingTasks);
}
catch (Exception ex)
{
Notes.Text += ex.Message + Environment.NewLine;
}
finally
{
cancellationTokenSource = null;
}
}
private async void Search_Click(object sender, RoutedEventArgs e)
{
#region Before loading stock data
var watch = new Stopwatch();
watch.Start();
StockProgress.Visibility = Visibility.Visible;
StockProgress.IsIndeterminate = true;
Search.Content = "Cancel";
#endregion
#region Cancellation
if (cancellationTokenSource != null)
{
cancellationTokenSource.Cancel();
cancellationTokenSource = null;
return;
}
cancellationTokenSource = new CancellationTokenSource();
cancellationTokenSource.Token.Register(() =>
{
Notes.Text += "Cancellation requested" + Environment.NewLine;
});
#endregion
try
{
#region Load One or Many Tickers
var tickers = Ticker.Text.Split(',', ' ');
var service = new StocksService();
var tickerLoadingTasks = new List <Task <IEnumerable <StockPrice> > >();
foreach (var ticker in tickers)
{
var loadTask = service.GetStockPricesFor(ticker, cancellationTokenSource.Token);
tickerLoadingTasks.Add(loadTask);
}
#endregion
// Stocks loaded - now need processing
var loadedStocks = await Task.WhenAll(tickerLoadingTasks);
// Use threadsafe collection
var values = new ConcurrentBag <StockCalculation>();
// Standard foreach loop converted into a Parallel foreach
// Includes guidance on max number of concurrent tasks
var exResult = Parallel.ForEach(loadedStocks,
new ParallelOptions {
MaxDegreeOfParallelism = 4
},
(stocks, state) =>
{
var stockName = stocks.First().Ticker;
// Will break out of current thread
// Will not execute outstanding iterations
// On-going tasks will not be stopped
// return - explicitly return from current thread context
if (stockName == "MBI")
{
state.Break();
return;
}
var result = CalculateExpensiveComputation(stocks);
var data = new StockCalculation
{
Ticker = stocks.First().Ticker,
Result = result
};
values.Add(data);
});
if (exResult.IsCompleted)
{
Stocks.ItemsSource = values;
}
else
{
Notes.Text = "Parallel computation of stocks did not complete successfully";
}
// Calculate total stock price for each ticker
decimal totalStocksValue = 0;
exResult = Parallel.For(0, loadedStocks.Length, i =>
{
var value = 0m;
foreach (var s in loadedStocks[i])
{
// 1. Unstable: totalStocksValue += Compute(s);
// 2. Fix, but limited solution:
// Interlocked.Add(ref totalStocksValue, (int)Compute(s));
// 3. Minimise code inside lock
value += Compute(s);
}
lock (syncRoot)
{
totalStocksValue += value;
}
});
Notes.Text = $"Stock price total: {totalStocksValue:N2}";
}
catch (Exception ex)
{
Notes.Text += ex.Message + Environment.NewLine;
}
finally
{
cancellationTokenSource = null;
}
#region After stock data is loaded
StocksStatus.Text = $"Loaded stocks for {Ticker.Text} in {watch.ElapsedMilliseconds}ms";
StockProgress.Visibility = Visibility.Hidden;
Search.Content = "Search";
#endregion
}