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POMaking TPL Async calls from mvc controller on click of submit button
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  1. POMaking TPL Async calls from mvc controller on click of submit button
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    copied!<p>Basically I want to implement simple search functionality, whenever user enters some keyword in the text box on view and clicks submit button I want to make ASYNC calls to predefined website urls using TPL Async mechanism. When I do the same with console application it works like a charm but not with ASP.NET MVC3.</p> <p>I couldn't find the reason</p> <pre><code> public ActionResult Index() { ViewBag.Message = "Welcome to ASP.NET MVC!"; return View(); } public ActionResult About() { return View(); } [HttpPost] public ActionResult Index(string text) { string[] url = { "http://www.msnbc.com", "http://www.yahoo.com", "http://www.nytimes.com", "http://www.washingtonpost.com", "http://www.latimes.com", "http://www.newsday.com" }; Task&lt;string[]&gt; webTask = this.GetWordCounts(url, text); string[] results = null; try { results = webTask.Result; } catch (AggregateException e) { } return View("Index", results); } //Taken from MSDN Task&lt;string[]&gt; GetWordCounts(string[] urls, string name) { TaskCompletionSource&lt;string[]&gt; tcs = new TaskCompletionSource&lt;string[]&gt;(); WebClient[] webClients = new WebClient[urls.Length]; object m_lock = new object(); int count = 0; List&lt;string&gt; results = new List&lt;string&gt;(); for (int i = 0; i &lt; urls.Length; i++) { webClients[i] = new WebClient(); #region callback // Specify the callback for the DownloadStringCompleted // event that will be raised by this WebClient instance. webClients[i].DownloadStringCompleted += (obj, args) =&gt; { if (args.Cancelled == true) { tcs.TrySetCanceled(); return; } else if (args.Error != null) { // Pass through to the underlying Task // any exceptions thrown by the WebClient // during the asynchronous operation. tcs.TrySetException(args.Error); return; } else { // Split the string into an array of words, // then count the number of elements that match // the search term. string[] words = null; words = args.Result.Split(' '); string NAME = name.ToUpper(); int nameCount = (from word in words.AsParallel() where word.ToUpper().Contains(NAME) select word) .Count(); // Associate the results with the url, and add new string to the array that // the underlying Task object will return in its Result property. results.Add(String.Format("{0} has {1} instances of {2}", args.UserState, nameCount, name)); } // If this is the last async operation to complete, // then set the Result property on the underlying Task. lock (m_lock) { count++; if (count == urls.Length) { tcs.TrySetResult(results.ToArray()); } } }; #endregion // Call DownloadStringAsync for each URL. Uri address = null; try { address = new Uri(urls[i]); // Pass the address, and also use it for the userToken // to identify the page when the delegate is invoked. webClients[i].DownloadStringAsync(address, address); } catch (UriFormatException ex) { // Abandon the entire operation if one url is malformed. // Other actions are possible here. tcs.TrySetException(ex); return tcs.Task; } } // Return the underlying Task. The client code // waits on the Result property, and handles exceptions // in the try-catch block there. return tcs.Task; } </code></pre> <p>this is my view - for now I have hard coded keyword as microsoft</p> <pre><code>@using (Html.BeginForm("Index", "Home", new { text = "Microsoft" })) { &lt;input type="submit" /&gt; } </code></pre> <p>Update: It stays forever and inside the try block of Index Post method</p>
 

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