Webcast: Asynchronous Programming Demystified

Webcast: Asynchronous Programming Demystified

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  Asynchronous Programming Demystified 1/14/2015 http://submain.com/webcasts/asynchronous-programming-demystified/ for thewebcast recording, slides and demo code download
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  Webcast Housekeeping 1/14/2015 Audio  ConnectviaVoIP  Plug in a headset or turn up your speakers  Connect via Phone  Select “UseTelephone” after joining the webinar  Call 1 (415) 655-0053 Access Code: 805-361-561 Audio PIN: Shown after joining the webinar Asking A Question  Use the Questions window in the panel on the right of your screen  Questions will be addressed at the end of the webcast Recording  A recording download link will be sent to all registrants within a few days Copyright © SubMain 2015 2
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  Agenda 1/14/2015  Overview ofAsync Patterns  Introduction to async/await  Asynchrony and Parallelism  Benefits of async/await  Demo  Future Async webinars  Q&A Copyright © SubMain 2015 3
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  Introduction Presenter Stephen Cleary Microsoft MVP (g)host SergeBaranovsky Principal, SubMain 1/14/2015 Copyright © SubMain 2015 4
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  Stephen Cleary stephencleary.com C# MicrosoftMVP Concurrency in C# Cookbook (O’Reilly) 1/14/2015 Copyright © SubMain 2015 5
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  Introduction to async/await 1/14/2015Copyright © SubMain 2015 6
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  Overview of AsyncPatterns Async/await use theTask-basedAsync Pattern (TAP)  Task SampleAsync(); Older: Event-based Async Pattern (EAP)  void SampleAsync();  event SampleCompleted; Older: Async Programming Model (APM)  IAsyncResult BeginSample();  EndSample(); 1/14/2015 Copyright © SubMain 2015 7
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  Syntax Pair of keywords(async + await) 1/14/2015 int Test() { Thread.Sleep(100); return 13; } async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 8
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  What “async” means Enablesthe await keyword in that method. Creates a state machine for the method. 1/14/2015 async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 9
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  What “await” means Anawait expression takes one argument – an “awaitable” (usually aTask orTask<T>).  This “awaitable” represents an asynchronous operation. 1/14/2015 async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 10 async Task<int> TestAsync() { var delayTask = Task.Delay(100); await delayTask; return 13; }
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  What “await” means Awaitwill pause its async method until the operation completes.  If operation is already completed -> don’t pause.  If operation faults -> raise exception. Resume executing in a captured context by default. 1/14/2015 async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 11
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  What “await” means Whenawait pauses:  Returns an incomplete task to its caller. When async method completes:  Completes the task that was returned earlier. The task represents the method. 1/14/2015 async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 12
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  Captured Context When awaitresumes:  SynchronizationContext.Current orTaskScheduler.Current What that means in practice:  UI context, ASP.NET request context, or thread pool. Avoiding context: use ConfigureAwait(false). 1/14/2015 async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 13
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  What “await” doesn’tmean Nothing to do with threads.  Not at all like “asynchronous delegates”.  Does not run the code on a background thread.  Does not parallelize your code. 1/14/2015 async Task<int> TestAsync() { await Task.Delay(100); return 13; } Copyright © SubMain 2015 14
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  Asynchrony != Parallelism Eachhave their uses.  Asynchrony – I/O, events.  Parallelism – CPU-bound processing. 1/14/2015 Copyright © SubMain 2015 15 Concurrency Asynchrony Parallelism
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  Benefits of async/await Responsiveness on the client side  Scalability on the server side  Naturally-asynchronous code has async APIs  Naturally-synchronous code stays synchronous  Asynchronous code is clean – no callbacks! 1/14/2015 Copyright © SubMain 2015 16
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  What is CodeIt.Right 1/14/2015Copyright © SubMain 2015 17
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  What is CodeIt.Right Code Quality Analysis and Metrics  Automated Code Review process  Automated way to discover and fix code smells  Automatic and safe refactoring of issues into conforming code  Ensure your code adheres to (your) predefined design requirements and best coding practices 1/14/2015 Copyright © SubMain 2015 18
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  What is CodeIt.Right- continued Instant Code Review – real-time code checking OnDemand Analysis Source Control Check-In Policy Build Process Integration Hundreds of rules  Security, Performance, Usage, Design, Maintainability, Exception Handling, Globalization, Async, and more 1/14/2015 Copyright © SubMain 2015 19
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  Demo Demo #1 –Correct async code Demo #2 – Async naming convention Demo #3 – Async void Demo #4 – Blocking on async code Demo #5 – Async code blocking Demo #6 – Fake-async code Demo #7 – Using ContinueWith 1/14/2015 Copyright © SubMain 2015 20 http://submain.com/webcasts/asynchronous-programming-demystified/ for the webcast recording, slides and demo code download
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  Asynchronous Programming Async confusing?CodeIt.Right will guide  CodeIt.Right Async rule set:  Async method should have "Async" suffix  Async method should have await statement  Async method should returnTask orTask<T>  Async method - avoid "out" and "ref" parameters  Async method - await for completion  Await statement - method should be async  Async method - call Start on theTask  Async method - do not useTask.Yield  Async method - do not useTask.Wait  Async method should not be Sub  Async method parameters should be the same to synchronous counterpart  Async method - transform to non-async if simple 1/14/2015 Copyright © SubMain 2015 22
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  Poll  Future Asyncwebinars 1/14/2015 Copyright © SubMain 2015 23
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  Q&A Questions? Email - customer-service@submain.com Video- submain.com/codeit.right/video Download the free CodeIt.Right trial at submain.com/codeit.right Contact Stephen Cleary: stephencleary.com 1/14/2015 1 (800) 936-2134 Copyright © SubMain 2015 24 http://submain.com/webcasts/asynchronous-programming-demystified/ for the webcast recording, slides and demo code download