Question

I have this sample code.

List<Dictionary<string,string>> objects = new List<Dictionary<string,string>>();

foreach (string url in urls)
{
    objects.add(processUrl(url))
}

I need to process the URL, processUrl down load the page and run many regex to extract some informations and return a “C# JSON like” object, so I want to run this in parallels and in the end I need a list of objects so i need to wait all tasks to continue process, how can I accomplish this? I se many example but none saving the return.

Regards

Answer 1

Like this?

var results = urls.AsParallel().Select(processUrl).ToList();

With Parallel:

Parallel.ForEach(
    urls, 
    url =>
    {
        var result = processUrl(url);
        lock (syncOjbect)
            objects.Add(result);
    };

or

var objects = new ConcurrentBag<Dictionary<string,string>>();
Parallel.ForEach(urls, url => objects.Add(processUrl(url)));
var result = objects.ToList();

or with Tasks:

var tasks = urls
    .Select(url => Task.Factory.StartNew(() => processUrl(url)))
    .ToArray();

Task.WaitAll(tasks);
var restuls = tasks.Select(arg => arg.Result).ToList();