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Async #1 – New In VS11Lucian Wischik, Senior Program Manager (VB)Microsoft Corporation

NDC 2012

A Language For Each Generation

Basic, C, AsmVB, C++, Delphi, C# AsyncFortran, Cobol

1960Mainframe

1980Microcomputer

1990Desktop

2010Distributed

A Language For Each Generation

Basic, C, AsmVB, C++, Delphi, C# AsyncFortran, Cobol

please wait for the next slideclicking won’t make it come any faster

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void LoadSettings() { IO.File.ReadAllText(path);}

void Button1_Click() { LoadSettings(); UpdateView();}

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Introducing AsyncM

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void LoadSettings() { IO.Network.Download(path);}

void Button1_Click() { LoadSettings(); UpdateView();}

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Introducing AsyncM

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Plan of talk

1. Introduce asyncWhy make things async

How to make things async

Message pump

UI thread deadlock

Avoid re-entrancy

Async unit test

Multi-threaded sync context

3. Deep DiveHow it works

What next

2. Task Async PatternAsync Function FooAsync() As Task

Q & ATask.Run

Task.WhenAny

Task.WhenAll

Cancellation

DemoAdd the Async & Await keywords

async Task LoadSettingsAsync() { await IO.Network.DownloadAsync(path);}

void LoadSettings() { IO.Network.Download(path);}

async void Button1_Click() { await LoadSettingsAsync(); UpdateView();}

void Button1_Click(..) { LoadSettings(); UpdateView();}

Introducing AsyncM

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async Task LoadSettingsAsync() { await IO.Network.DownloadAsync(path);}

async void Button1_Click(){ await LoadSettingsAsync(); UpdateView();}

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Explaining AsyncM

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Task ...DownloadAsync

Task ...LoadSettingsAsync

Download

LoadSettings

DemoAsync UI app: re-entrancy and deadlockAsync unit testAsync console app

Introduce asyncWhy make things async

How to make things async

Message pump

Deadlock if block on UI thread

Avoid re-entrancy

The UI message-pump is the key to async

Photo: Rüdiger Wölk

Plan of talk

2. Task Async PatternAsync Function FooAsync() As Task

1. Introduce asyncWhy make things async

How to make things async

Message pump

UI thread deadlock

Avoid re-entrancy

Async unit test

Multi-threaded sync context

3. Deep DiveHow it works

What next

Q & ATask.Run

Task.WhenAny

Task.WhenAll

Cancellation

DemoUsing the Task type for compositional algorithmsCancellation

Task Async Pattern

Async Sub vs Async Function

Task.Run Task.WhenAny

Taks.WhenAll

Using Async

T.A.P.Function FooAsync() As Task.Only use Async Sub for top-level events.

Task type is a “promise”It represents a result that hasn’t yetbeen computed. A-syn-chronos.

Task is compositionalUse it to build sophisticated behavior.

Text/PicPictures can set a mood orevoke emotion, making fora more memorable presentation.

The task type is a “promise” of future results

Plan of talk

3. Deep DiveHow it works

What next

Q & A

2. Task Async PatternAsync Function FooAsync() As Task

1. Introduce asyncWhy make things async

How to make things async

Message pump

UI thread deadlock

Avoid re-entrancy

Async unit test

Multi-threaded sync context

Task.Run

Task.WhenAny

Task.WhenAll

Cancellation

This is the IL that’s emitted whenyou use async/await

Async: how it works

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

UIthread IOCP

thread

Async: How it works

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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[1/12] A button-click arrives on the UI queue

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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downTask

[2/12] Invoke some functions; get back “downTask” from the API

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

downTask

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

UIthread IOCP

thread

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downTask » sc.Post{Κ1}

[3/12] “Await downTask” assigns a continuation and returns loadTask

loadTask

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

loadTask

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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downTask » sc.Post{Κ1}

[4/12] “Await loadTask” assigns a continuation and returns

Κ2:

loadTask » sc.Post{Κ2}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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conf

[5/12] Network packet arrives with data

downTask » sc.Post{Κ1}

Κ2:

loadTask » sc.Post{Κ2}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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confsc.Post{Κ1(conf)}

[6/12] Invoke downTask’s continuation with that data

downTask » sc.Post{Κ1}

Κ2:

loadTask » sc.Post{Κ2}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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loadTask » sc.Post{Κ2}

conf

K1(conf)

[7/12] Continuation is a “Post”, i.e. addition to the UI queue

Κ2:

sc.Post{Κ1(conf)}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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conf

K1(conf)

[8/12] UI thread executes K1

Κ2:

sc.Post{Κ1(conf)}

loadTask » sc.Post{Κ2}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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conf

K1(conf)

[9/12] Return statement will signal completion of loadTask

Κ2:

sc.Post{Κ1(conf)}

loadTask » sc.Post{Κ2}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

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conf

K1(conf)

sc.Post(Κ2(len))

[10/12] Invoke loadTask’s continuation with data (by posting to UI queue)

K2(len) Κ2:

sc.Post{Κ1(rss)}

loadTask » sc.Post{Κ2}

Κ1:

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

UIthread IOCP

thread

Click

conf

K1(rss)

sc.Post(Κ2(len))

K2(len)

[11/12] Return from handling the K1 continuation

Κ2:

sc.Post{Κ1(conf)}

Κ1:

Async Task<int> LoadSettingsAsync() {

Button1.IsEnabled = False;

var downTask = IO.Network.DownloadAsync(path);

this.Config = await downTask;

return this.Config.Length;

}

async void Button1_Click() { var loadTask = LoadSettingsAsync();

var len = await loadTask;

UpdateView();}

conf

K2(len)

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K1(rss)

UIthread IOCP

thread

sc.Post(Κ2(len))

Κ1:

Κ2:

[12/12] UI thread executes K2

sc.Post{Κ1(conf)}

“A waiter’s job is to wait on a table until the

patrons have finished their

meal.

If you want to serve two

tables concurrently, you must hire two waiters.”

The following is from the Android dev blog.Can you spot the flaw?

1. “A good practice in creating responsive applications is to make sure your main UI thread does the minimum amount of work.”

2. “Any potentially long task that may hang your application should be handled in a different thread.”

3. “Typical examples of such tasks are network operations, which involve unpredictable delays.”

Asynchrony & concurrency don’t need multiple threads

Windows Phone…

.NET4Silverlight5Use VS2012 RC +Async Targeting Pack

.NET45Windows8Use VS2012 RC

T.A.P.From today onwards, all async library code you write should return Task.

What next to start using async

Q & A

Get VS2012 RChttp://msdn.microsoft.com/vstudio

Task Asynchronous Patternhttps://www.microsoft.com/download/en/details.aspx?id=19957http://www.wischik.com/lu/AsyncSilverlight/http://social.msdn.microsoft.com/Forums/async

Async Targeting Packhttp://msdn.microsoft.com/async

Downloads from this talkhttp://blogs.msdn.com/lucian

© 2012 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.