1. Pavel Yosifovich Hi-Tech College pavely@hi-tech.co.il http://blogs.microsoft.co.il/blogs/pavely

2. C# Evolution Trends Synchronous vs. Asynchronous Asynchrony the “old way” The New Way Odds and Ends Summary

3. C# 1.0 Managed Code C# 2.0 Generics C# 3.0 Language Integrated Query C# 4.0 Dynamic Typing

4. Declarative ConcurrentDynamic

5. Increasingly connected applications More latency More UI responsiveness problems More scalability issues Asynchronous programming Becoming the norm in responsive, scalable apps Async-only APIs, e.g. JavaScript and Silverlight

6. C# 1.0 Managed Code C# 2.0 Generics C# 3.0 Language Integrated Query C# 4.0 Dynamic Typing Asynchronous Programming C# v.Next

8. Synchronous  Wait for result before returning string DownloadString(...); Asynchronous  Return now, call back with result void DownloadStringAsync(..., Action callback); Asynchronous work != Threads

9. var data = DownloadData(...); ProcessData(data); var data = DownloadData(...); ProcessData(data); DownloadDataAsync(..., data => { ProcessData(data); }); DownloadDataAsync(..., data => { ProcessData(data); });

10. var data = DownloadData(...); ProcessData(data); var data = DownloadData(...); ProcessData(data); DownloadDataAsync(..., data => { ProcessData(data); }); DownloadDataAsync(..., data => { ProcessData(data); });

11. Goal: Just like synchronous programming Framework: Use Task for all asynchrony Add Task support to existing.NET and Silverlight APIs Developers can do the same Languages: Asynchronous Methods “async” modifier marks method or lambda as asynchronous “await” operator yields control until awaited task completes

12. Represents “ongoing operation” Could be async I/O, background worker, anything... Single object for status, result and exceptions Composable callback model var task2 = task1.ContinueWith(t => … t.Result …); The “await” operator rewrites to continuations Combinators WhenAll, WhenAny, Delay, etc.

13. async void DoWorkAsync() { var t1 = ProcessFeedAsync("www.acme.com/rss"); var t2 = ProcessFeedAsync("www.xyznews.com/rss"); await Task.WhenAll(t1, t2); DisplayMessage("Done"); } async void DoWorkAsync() { var t1 = ProcessFeedAsync("www.acme.com/rss"); var t2 = ProcessFeedAsync("www.xyznews.com/rss"); await Task.WhenAll(t1, t2); DisplayMessage("Done"); } async Task ProcessFeedAsync(string url) { var text = await DownloadFeedAsync(url); var doc = ParseFeedIntoDoc(text); await SaveDocAsync(doc); ProcessLog.WriteEntry(url); } async Task ProcessFeedAsync(string url) { var text = await DownloadFeedAsync(url); var doc = ParseFeedIntoDoc(text); await SaveDocAsync(doc); ProcessLog.WriteEntry(url); }

14. async void DoWorkAsync() { var t1 = ProcessFeedAsync("www.acme.com/rss"); var t2 = ProcessFeedAsync("www.xyznews.com/rss"); await Task.WhenAll(t1, t2); DisplayMessage("Done"); } async void DoWorkAsync() { var t1 = ProcessFeedAsync("www.acme.com/rss"); var t2 = ProcessFeedAsync("www.xyznews.com/rss"); await Task.WhenAll(t1, t2); DisplayMessage("Done"); } async Task ProcessFeedAsync(string url) { var text = await DownloadFeedAsync(url); var doc = ParseFeedIntoDoc(text); await SaveDocAsync(doc); ProcessLog.WriteEntry(url); } async Task ProcessFeedAsync(string url) { var text = await DownloadFeedAsync(url); var doc = ParseFeedIntoDoc(text); await SaveDocAsync(doc); ProcessLog.WriteEntry(url); }

15. async Task ProcessFeedAsync(string url) { var text = await DownloadFeedAsync(url); var doc = ParseFeedIntoDoc(text); await SaveDocAsync(doc); ProcessLog.WriteEntry(url); } async Task ProcessFeedAsync(string url) { var text = await DownloadFeedAsync(url); var doc = ParseFeedIntoDoc(text); await SaveDocAsync(doc); ProcessLog.WriteEntry(url); }

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30. Should be as simple as the synchronous case var wc = new WebClient(); try { string txt = await wc.DownloadStringTaskAsync(url); dataTextBox.Text = txt; } catch(WebException x) { // Handle as usual } var wc = new WebClient(); try { string txt = await wc.DownloadStringTaskAsync(url); dataTextBox.Text = txt; } catch(WebException x) { // Handle as usual }

31. async Task GetRssAsync(string url) { var client = new WebClient(); var task = client.DownloadStringTaskAsync(url); var text = await task; var xml = XElement.Parse(text); return xml; } async Task GetRssAsync(string url) { var client = new WebClient(); var task = client.DownloadStringTaskAsync(url); var text = await task; var xml = XElement.Parse(text); return xml; }

32. async Task GetRssAsync(string url) { var client = new WebClient(); var task = client.DownloadStringTaskAsync(url); var text = await task; var xml = XElement.Parse(text); return xml; } async Task GetRssAsync(string url) { var client = new WebClient(); var task = client.DownloadStringTaskAsync(url); var text = await task; var xml = XElement.Parse(text); return xml; } Task GetRssAsync(string url) { var $builder = AsyncMethodBuilder.Create(); var $state = 0; TaskAwaiter $a1; Action $resume = delegate { try { if ($state == 1) goto L1; var client = new WebClient(); var task = client.DownloadStringTaskAsync(url); $state = 1; $a1 = task.GetAwaiter(); if ($a1.BeginAwait($resume)) return; L1: var text = $a1.EndAwait(); var xml = XElement.Parse(text); $builder.SetResult(xml); } catch (Exception $ex) { $builder.SetException($ex); } }; $resume(); return $builder.Task; } Task GetRssAsync(string url) { var $builder = AsyncMethodBuilder.Create(); var $state = 0; TaskAwaiter $a1; Action $resume = delegate { try { if ($state == 1) goto L1; var client = new WebClient(); var task = client.DownloadStringTaskAsync(url); $state = 1; $a1 = task.GetAwaiter(); if ($a1.BeginAwait($resume)) return; L1: var text = $a1.EndAwait(); var xml = XElement.Parse(text); $builder.SetResult(xml); } catch (Exception $ex) { $builder.SetException($ex); } }; $resume(); return $builder.Task; }

33. As simple as synchronous code Unifies computational, network and I/O asynchrony More scalable servers More responsive UI

34. C# 1.0 Managed Code C# 2.0 Generics C# 3.0 Language Integrated Query C# 4.0 Dynamic Typing Asynchronous Programming C# v.Next

35. Class Field public Foo private string X X Compiler Source code Source File Source code.NET Assembly Meta-programmingRead-Eval-Print Loop Language Object Model DSL Embedding

36. Visual Studio Async CTP http://msdn.com/vstudio/async Eric Lippert’s Blog http://blogs.msdn.com/b/ericlippert/ The Async CTP does not currently work if SP1 is installed Need to install on top of the RTM version A new CTP will probably be released soon that will work with SP1