Building IIS and ASP.NET apps with the power of async

SAC-804T Building IIS and ASP.NET apps with the power of async Damian Edwards, Phil Haack Program Managers, ASP.NET Microsoft Corporation

Agenda slide WHO WILL BENEFIT FROM THIS TALK TOPICS WHAT YOU’LL LEAVE WITH • How to use asyncprogramming in ASP.NET to increase scalability, improve page response time and implement long running requests • The Task Parallel Library (TPL) and async/await support in in C# and .NET 4.5 makes programming async much easier than traditional APM • ASP.NET 4.5, including the core framework, Web Forms and MVC, has great support for working with the TPL and async/await • History of async programming in .NET • How async works in ASP.NET • Using async in ASP.NET apps • ASP.NET developers, including Web Forms & MVC

A brief history of async programming in .NET

Three async programming models Asynchronous Programming Model (APM) Evented Asynchronous Programming (EAP) Task-based Asynchronous Programming (TAP)

Asynchronous Programming Model (APM) Asynchronous Programming Model (APM) // .NET 1 model file.BeginRead(buffer, 0, maxLength, asyncResult => { intnumBytesRead = file.EndRead(asyncResult); // Now do something with "buffer“ }, null);

Event-based Asynchronous Programming (EAP) // .NET 2 model webClient.DownloadStringCompleted += (sender, args) => { string html = args.Result; // Now do something with "html" }; webClient.DownloadStringAsync(newUri("http://example.com"));

Task-based Asynchronous Programming (TAP) Task<string> htmlTask= webClient.DownloadStringTaskAsync(url); string html = htmlTask.Result; // Sync (block until done) htmlTask.ContinueWith(task => { string html = task.Result; // Async, C# 4 }); string html = awaithtmlTask; // Async, C# 5

How C# 5 “async” works publicasyncTask<ViewResult> MyMethod() { stringmyParam = "some value"; var data = awaitFetchSomeData(myParam); return View(data); } Before compilation 1 2 After compilation (conceptual) publicTask<ViewResult> MyMethod() { stringmyParam = "some value"; return FetchSomeData(myParam).ContinueWith(task => { vardata = task.Result; return View(data); }); } 1 2

How async requests work in ASP.NET

Traditional Web request handling “thread-per-request” a.k.a. “post office” Requests Thread pool Busy Busy Busy Busy

Asynchronous Web request handling a.k.a. “restaurant” Requests Thread pool

Using async for benefit in ASP.NET apps. Easy as 1, 3, 2

So can I just use async everywhere in my ASP.NET app? No!

There are three (3) distinct scenarios where async in ASP.NET apps might be useful…

demo Async IO in ASP.NET

demo Parallelizing work for faster request throughput

demo Handling long running, event driven requests

For more information RELATED SESSIONS DOCUMENTATION & ARTICLES http://www.asp.net/vnext TOOL-810T: Async made simple in Windows 8, with C# and Visual Basic

thank you Feedback and questions http://forums.dev.windows.com Session feedbackhttp://bldw.in/SessionFeedback

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Building IIS and ASP.NET apps with the power of async