<\/p>\n (The full set of ParallelExtensionsExtras Tour posts is available here<\/span><\/a><\/span><\/span><\/em>.)<\/span><\/em><\/span><\/p>\n <\/span><\/span><\/span><\/span><\/span><\/span><\/p>\n <\/span><\/span><\/p>\n The Task Parallel Library isn’t just about CPU-bound operations. <\/span>The Task class is a great representation for any asynchronous operation, even those implemented purely as asynchronous I\/O.<\/p>\n <\/span><\/span><\/p>\n Task’s ability to represent arbitrary asynchronous operations without tying up threads is rooted in the TaskCompletionSource<TResult> class (previously discussed <\/span>here<\/span><\/a>), and this becomes a building block for creating an unlimited number of higher-level asynchronous operations represented as a Task. <\/span>ParallelExtensionsExtras<\/span><\/a> includes a wealth of such implementations, and for the next several blog posts in this <\/span>ParallelExtensionsExtras Tour<\/span><\/a> series, we’ll examine several implementations as well as how they can be used in your own projects that require asynchrony.<\/p>\n <\/span><\/span><\/p>\n The ParallelExtensionsExtrasExtensionsEAP folder contains three useful files: WebClientExtensions.cs, SmtpClientExtensions.cs, and PingExtensions.cs. <\/span>As you might guess, these files contain extension methods for the System.Net.WebClient, System.Net.Mail.SmtpClient, and System.Net.NetworkInformation.Ping classes. <\/span>These extension methods mirror the existing asynchronous methods on these types (which all implement the Event-Based Asynchronous Pattern), but rather than forcing you to first register for some events and then call a method to kick off the download, they simply return task-based representations. <\/span>For example, WebClientExtensions provides the following method, which will download the data at the specified address and return a Task<byte[]> to represent the result:<\/p>\n <\/span><\/span><\/p>\n public<\/span> static<\/span> Task<\/span><byte<\/span>[]> DownloadDataTask(<\/p>\n <\/span><\/p>\n <\/span>this<\/span> WebClient<\/span> webClient, string<\/span> address);<\/p>\n <\/span><\/p>\n <\/p>\n <\/span><\/p>\n <\/span><\/p>\n With a method like this, you can very easily download a single file, but you can now also take advantage of the power of the Task class to, for example, download multiple files and perform a follow-up operation asynchronously only when all of the asynchronous downloads have completed, in this case outputting some diagnostic information about each download’s success or failure, e.g.<\/p>\n <\/span><\/span><\/span><\/p>\n <\/p>\n <\/span><\/p>\n <\/span><\/p>\n Task<\/span>.Factory.ContinueWhenAll(new<\/span>[]<\/p>\n <\/span><\/p>\n {<\/p>\n <\/span><\/p>\n <\/span>new<\/span> WebClient<\/span>().DownloadDataTask(“http:\/\/www.microsoft.com”<\/span>),<\/p>\n <\/span><\/p>\n <\/span>new<\/span> WebClient<\/span>().DownloadDataTask(“https:\/\/blogs.msdn.com\/pfxteam”<\/span>),<\/p>\n <\/span><\/p>\n <\/span>new<\/span> WebClient<\/span>().DownloadDataTask(“https:\/\/msdn.com\/concurrency”<\/span>)<\/p>\n <\/span><\/p>\n },<\/p>\n <\/span><\/p>\n tasks =><\/p>\n <\/span><\/p>\n {<\/p>\n <\/span><\/p>\n <\/span>\/\/ All tasks completed; look at the result for each<\/span><\/p>\n <\/span><\/p>\n <\/span>foreach<\/span> (var<\/span> task in<\/span> tasks)<\/p>\n <\/span><\/p>\n <\/span>{<\/p>\n <\/span><\/p>\n <\/span>\/\/ Print out information about each download<\/span><\/p>\n <\/span><\/p>\n <\/span>Console<\/span>.WriteLine(“Address: “<\/span> + task.AsyncState);<\/p>\n <\/span><\/p>\n <\/span>if<\/span> (task.IsFaulted) <\/p>\n <\/span><\/p>\n <\/span><\/span>Console<\/span>.WriteLine(“tFailed: {0}”<\/span>, <\/p>\n <\/span><\/p>\n <\/span><\/span>task.Exception.InnerException.Message);<\/p>\n <\/span><\/p>\n <\/span>else<\/span> <\/p>\n <\/span><\/p>\n <\/span>Console<\/span>.WriteLine(“tDownloaded {0} bytes”<\/span>, <\/p>\n <\/span><\/p>\n <\/span><\/span>task.Result.Length);<\/p>\n <\/span><\/p>\n <\/span>}<\/p>\n <\/span><\/p>\n });<\/p>\n <\/span><\/p>\n <\/p>\n <\/span><\/p>\n <\/span><\/p>\n As another example, the PingExtensions class provides the extension method:<\/p>\n <\/span><\/span><\/span><\/p>\n <\/p>\n <\/span><\/p>\n <\/span><\/p>\n <\/span>public<\/span> static<\/span> Task<\/span><PingReply<\/span>> SendTask( <\/span><\/p>\n <\/p>\n <\/span><\/p>\n <\/span><\/p>\n This makes it easy to send multiple pings asynchronously and work with the resulting task objects, e.g.<\/p>\n <\/span><\/span><\/span><\/p>\n <\/p>\n <\/span><\/p>\n <\/span><\/p>\n var<\/span> addresses = new<\/span>[] <\/p>\n <\/span><\/p>\n {<\/p>\n <\/span><\/p>\n <\/span>“localhost”<\/span>,<\/p>\n <\/span><\/p>\n <\/span>“microsoft.com”<\/span>,<\/p>\n <\/span><\/p>\n <\/span>“msdn.com”<\/span><\/p>\n <\/span><\/p>\n };<\/p>\n <\/span><\/p>\n <\/p>\n <\/p>\n <\/span><\/p>\n var<\/span> pings = (from<\/span> address in<\/span> addresses <\/p>\n <\/span><\/p>\n <\/span> <\/span>select<\/span> new<\/span> Ping<\/span>().SendTask(address)).ToArray();<\/p>\n <\/span><\/p>\n foreach<\/span> (var<\/span> ping in<\/span> pings)<\/p>\n <\/span><\/p>\n {<\/p>\n <\/span><\/p>\n <\/span>\/\/ Print out each ping as it succeeds or fails<\/span><\/p>\n <\/span><\/p>\n <\/span>ping.ContinueWith(t =><\/p>\n <\/span><\/p>\n <\/span>{<\/p>\n <\/span><\/p>\n <\/span>Console<\/span>.WriteLine(“Ping for {0}: {1}”<\/span>, t.AsyncState, <\/p>\n <\/span><\/p>\n <\/span>t.IsFaulted ? <\/p>\n <\/span><\/p>\n <\/span>t.Exception.InnerException.Message : <\/p>\n <\/span><\/p>\n <\/span>t.Result.Status.ToString());<\/p>\n <\/span><\/p>\n <\/span>});<\/p>\n <\/span><\/p>\n }<\/span><\/p>\n
this<\/span> Ping<\/span> ping, string<\/span> hostNameOrAddress);<\/p>\n