private async Task <decimal> FetchPricesParallelAsync(IEnumerable <StockHolding> holdings)
{
decimal totalWorth = 0m;
var tasks = holdings.Select(
async holding => new { holding,
price = await priceService.LookupPriceAsync(holding.Ticker) })
.ToList();
foreach (var task in tasks.InCompletionOrder())
{
var result = await task;
var holding = result.holding;
var price = result.price;
Log("Price of {0}: {1}", holding.Ticker, price);
AddPortfolioEntry(
holding.Ticker, holding.Quantity,
price, holding.Quantity * price);
if (price != null)
{
totalWorth += holding.Quantity * price.Value;
}
}
return(totalWorth);
}
private async Task <decimal> CalculateWorthAsyncImpl(string user, string password)
{
var userId = await authenticationService.AuthenticateUserAsync(user, password);
if (userId == null)
{
throw new AuthenticationException("Bad username or password");
}
var portfolio = await portfolioService.GetPortfolioAsync(userId.Value);
decimal total = 0m;
#if !PARALLEL
#region Serial implementation
foreach (var item in portfolio)
{
var price = await priceService.LookupPriceAsync(item.Ticker);
if (price != null)
{
total += price.Value * item.Quantity;
}
}
#endregion
#else
#region Parallel implementation
var tasks = portfolio.Select(async holding => new
{
holding,
price = await priceService.LookupPriceAsync(holding.Ticker)
}).ToList();
foreach (var task in tasks.InCompletionOrder())
{
var result = await task;
var holding = result.holding;
var price = result.price;
if (price != null)
{
total += holding.Quantity * price.Value;
}
}
#endregion
#endif
return(total);
}
