C# 5 deep drive into asynchronous programming


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BDotnet Session on C# 5

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C# 5 deep drive into asynchronous programming

  1. 1. C# 5: Deep Drive intoAsynchronous Programming By- Praveen Kumar Prajapati Blog: praveenprajapati.wordpress.com
  2. 2. Agenda What’s asynchrony Related Terms and Need of Asynchrony Why TPL: The Free Lunch is Over C# 4: Task Parallel Library C# 4: TPL Demo C# 5 : Asynchronous Programming C# 5 : Behind the Scene C# 5 : Async Demo Summery
  3. 3. What’s asynchrony What’s asynchrony?  Greek origin  a (not)  syn (together with)  chronos (time)  Multiple parties evolving in time independently  Not being blocked Synchronous  Wait for result before returning  string DownloadString(...); Asynchronous  Return now, call back with result  void DownloadStringAsync(..., Action<string> callback);
  4. 4. Related Concepts Multithreading  Use of multiple threads Concurrency  Order in which multiple tasks execute is not determined Parallelism  True simultaneous execution (e.g. multicore)
  5. 5. Need of Asynchrony Increasingly connected applications  More latency  More UI responsiveness problems  More scalability issues Asynchronous programming  Becoming the norm in responsive, scalable apps  More relevant to Metro Style Apps and Window Phone Apps  Async-only APIs, e.g., JavaScript and Silverlight
  6. 6. Asynchronous Programming Model Hang UI Thread UI Messages DisplayPhotosDownloadDataAsync ParseResponse
  7. 7. Why TPL : The Free Lunch is Over A paradigm shift  Then: Faster clocks  Now: More cores => End of the Free Lunch The Free Lunch is Over  By Herb Sutter in Feb/Mar 2005  The Free Lunch Is Over -A Fundamental Turn Toward Concurrency in Software  Why You Don’t Have 10GHz Today
  8. 8. The Free Lunch is Over
  9. 9. Single to Multiple Core Transition
  10. 10. C# 4 : Task Parallel Library “Applications will increasingly need to be concurrent if they want to fully exploit continuing exponential CPU throughput gains” What would be the optimum number of threads for this machine? But how to decide the degree of concurrency? What if server gets more core in future – Change in underlying hardware?
  11. 11. C# 4 : Task Parallel Library The TPL scales the degree of concurrency dynamically to most efficiently use all the processors that are available. In addition, the TPL handles the partitioning of the work, the scheduling of threads on the ThreadPool, cancellation support, state management, and other low- level details. By using TPL, you can maximize the performance of your code while focusing on the work that your program is designed to accomplish.
  12. 12. Thread vs. Task Task: A Task is a future or a promise. (Some people use those two terms synonymously, some use them differently, nobody can agree on a precise definition.) Basically, a Task<T> "promises" to return you a T, but not right now . Thread: A Thread is one of many ways to fulfill that promise. But not every Task needs a Thread. If the value you are waiting for comes from the file system or a database or the network, then there is no need for a thread. The Task might just register a callback to receive the value when the disk is done seeking. TPL Demo
  13. 13. C# 5 : Asynchronous Programming New Keyword introduces:  async  Await Asynchronous Methods  As simple as synchronous code  Unifies computational, network and I/O asynchrony  More scalable servers  More responsive UI
  14. 14. C# 5 : Behind the Scenepublic async Task<XElement> GetXmlAsync(string url) { var client = new HttpClient(); var response = await client.GetAsync(url); var text = response.Content.ReadAsString(); return XElement.Parse(text);} public Task<XElement> GetXmlAsync(string url) { var tcs = new TaskCompletionSource<XElement>(); var client = new HttpClient(); client.GetAsync(url).ContinueWith(task => { var response = task.Result; var text = response.Content.ReadAsString(); tcs.SetResult(XElement.Parse(text)); }); return tcs.Task; }
  15. 15. C# 5 : Async Demo Demo: Use of async and await How it reduces efforts and make code better
  16. 16. Some Point to Remember For any async block it is important to have at least one await, otherwise the whole block will work synchronously. Any async method should postfix Async (as a rule), so your method name should look like MyMethodAsync which you put an async keyword before it. Exceptions to the convention can be made where an event, base class, or interface contract suggests a different name. Any async method can return void(call and forget), Task or Task<T> based on the Result the await method sends. Everything is managed by a State Machine Workflow by the compiler
  17. 17. Summery Asynchronous Programming and related terms Why it is so relevant in current days Free Lunch is Over TPL and Task New Kew words : async and await Rules and recommendation for new features
  18. 18. References• Visual Studio Asynchronous Programming http://msdn.microsoft.com/en-us/vstudio/async.aspx• Task Parallel Library http://msdn.microsoft.com/en-us/library/dd460717.aspx• The Future of C# and VB @PDC10 http://player.microsoftpdc.com/Session/1b127a7d-300e-4385-af8e-ac747fee677a• Fabulous Adventures in Coding http://blogs.msdn.com/b/ericlippert• John Skeet: Coding Blog http://msmvps.com/blogs/jon_skeet
  19. 19. Thanks to You AllLet us grow together Keep in touch: Blog: praveenprajapati.wordpress.com