1 / 5

Asynchronous programming

Asynchronous programming. Using Task, async and await. Responsive user interfaces. Users expect modern user interfaces to be responsive If the user interface must not “freeze” if the user starts a long-running task. Example long-running tasks Sending or receiving data on a network

elsa
Download Presentation

Asynchronous programming

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Asynchronous programming Using Task, async and await Asynchronous programming

  2. Responsive user interfaces • Users expect modern user interfaces to be responsive • If the user interface must not “freeze” if the user starts a long-running task. • Example long-running tasks • Sending or receiving data on a network • Communication with a potentially slow server • Including database servers, web servers, etc. • Performing time consuming calculations • Reading or writing files on the local hard disk • When the user initiates a task that is assumed to be long-running we must execute the task in a separate thread • “Separate” means not in the GUI thread Asynchronous programming

  3. Keywords: await and async • Two C# keywords: await + async • Syntax: await expression • Example: Await Task.whenAll(task1, task2, …., taskN) • Awaits termination of all task listed • await is used to await(!) the termination of a task • Normally waiting for the result of the task. • In the meantime the method that called the method containing the await will execute • When the awaited expression has terminated, control comes back to the method … • Which can then use the result to display, etc. • A method is declared asyncif there is an await statement inside the method • Example: GuiExampleAsyncWait Asynchronous programming

  4. API async methods • Some classes has support for async programming • Example: HttpClient • With HttpClient you can download the contents of a document specifying the documents URL • Task<string> getStringTask = httpClient.getStringAsync(“http://www.easj.dk/”); • String urlContents = await getStringTask; • http://msdn.microsoft.com/en-us/library/hh191443.aspx • Example: SimpleBrowserAsync • System.IO.Stream has some async methods Asynchronous programming

  5. References and further readings • MSDN Asynchronous Programming with Async and Await • http://msdn.microsoft.com/en-us/library/hh191443.aspx • John Sharp: Microsoft Visual C# 2012 Step by Step, • Chapter 24 Improving Response Time by Performing Asynchronous Operations, page 585-599 • Deitel & Deitel: Visual C# 2013, How To Programing, 5th edition, Pearson 2014 • Chapter 28 Asynchronous Programming with async and await, 26 pages • Available as a web-only chapter from http://www.pearsoninternationaleditions.com/Sitemap/Deitel/, Companion Web site • http://wps.pearsoned.co.uk/wps/media/access/Pearson_Default/15358/15727496/login.html Asynchronous programming

More Related