A Study and Toolkit for Asynchronous Programming in C#

We present the first study that analyzes the usage of asynchronous programming in a large experiment. We analyzed 1378 open source Windows Phone (WP) apps, comprising 12M SLOC, produced by 3376 developers. Using this data, we study the use and misuse of asynchronous constructs. Inspired by our findings, we developed (i) Asyncifier, an automated refactoring tool that converts callback-based asynchronous code to the new async/await; (ii) AsyncFixer, a tool that finds and corrects common misuses of async/await. For more, read our Distinguished Paper Award-winning ICSE'14 paper!
We also provide hundreds of real-world (mis)use examples of all asynchronous idioms and async/await!

A Study and Toolkit for Async in C#

We analyzed 1378 open source Windows Phone (WP) apps, comprising 12M SLOC, produced by 3376 developers. Inspired by this analysis findings, we developed (i) Asyncifier, an automated refactoring tool that converts callback-based asynchronous code to the new async/await; (ii) AsyncFixer, a tool that finds and corrects common misuses of async/await.

We present the first study that analyzes the usage of asynchronous libraries and new language constructs, async/await in a large experiment.

We analyzed:

1378 Windows Phone Apps

comprising

12M Source Lines of Code

produced by

3376 Developers

These are the Windows Phone applications that we studied: Application List.
We gathered these applications from Github and Codeplex by using our tool WPCollector.

(Mis)usage Examples of Asynchronous Idioms

Developers learn a new programming construct through both positive and negative examples. We provide hundreds of real-world examples of all asynchronous idioms. Because developers might need to inspect the whole source file or project to understand the example, we link to highlighted source files on GitHub.

Long-running CPU-Bound Operations
New Thread	Link to Usage Examples
Background Worker	Link to Usage Examples
Threadpool	Link to Usage Examples
New Task	Link to Usage Examples

Blocking I/O-Bound Operations
Callback-Based APM Idioms	Link to Usage Examples
Task-Based TAP Idioms with async/await	Link to Usage Examples

Misuse of Async/Await
Fire-Forget async Methods	Link to Usage Examples
Unnecessary async Methods	Link to Usage Examples
Long-running Operations Under async Methods	Link to Usage Examples
Unnecessarily Capturing Context Under async Methods	Link to Usage Examples

We developed (i) Asyncifier, an automated refactoring tool that converts callback-based asynchronous code to the new async/await;
(ii) AsyncFixer, a tool that finds and corrects common misuses of async/await.

Patches (Examples of Program Transformations)

We selected the most recently updated apps, applied Asyncifier and AsyncFixer ourselves, and offered the modifications to the original developers as a patch via a pull request. Developers accepted 314 patches generated by our tools.
ps: If the link to the patch or pull request is broken, it means that the application repository is removed from its hosting service.

Table 1: Asyncifier Transformations
App Name	Status	#	Link
TheOldReaderWP	ACCEPTED	5	Link to PR or Patch
Diettr-GPL	ACCEPTED	1	Link to PR or Patch
Ocell	ACCEPTED	3	Link to PR or Patch
phoneguitartab	ACCEPTED	3	Link to PR or Patch
HackerNews	ACCEPTED	4	Link to PR or Patch
Windows-Phone-Starter-Kit-for-RSS	ACCEPTED	1	Link to PR or Patch
SyncFramework-Toolkit	ACCEPTED	4	Link to PR or Patch
2ch-Browser-WP7	ACCEPTED	3	Link to PR or Patch
battlelogmobile	ACCEPTED	4	Link to PR or Patch
Ruminate	WAITING	1	Link to PR or Patch

Table 2 shows the applications which are selected to fix "Long-running operations under async methods". Table 3 shows the applications which are selected to fix "Unnecessary async/await methods". We did not especially select 10 apps to fix "Unnecessarily capturing context"; but AsyncFixer did fix this misuse in the selected apps, shown in Table 2 and Table 3.

Table 2: AsyncFixer Transformations - "Long-running operations under async methods"
App Name	Status	#	Link
kido-win	ACCEPTED	5	Link to PR or Patch
inspire	ACCEPTED	1	Link to PR or Patch
azure-wp-rest	ACCEPTED	3	Link to PR or Patch
Kinvey-WindowsPhone8	ACCEPTED	63	Link to PR or Patch
indulged-flickr	ACCEPTED	54	Link to PR or Patch
battlelogmobile	ACCEPTED	4	Link to PR or Patch
WindowsPhone-Common	ACCEPTED	1	Link to PR or Patch
kanboxwp	ACCEPTED	4	Link to PR or Patch
TheOldReaderWP	ACCEPTED	1	Link to PR or Patch
iRacer-MotionControl	was WAITING (now ACCEPTED)	1	Link to PR or Patch

Table 3: AsyncFixer Transformations - "Unnecessary async/await methods"
App Name	Status	#	Link
kido-win	ACCEPTED	47	Link to PR or Patch
Cimbalino-Phone-Toolkit	ACCEPTED	3	Link to PR or Patch
restafari	ACCEPTED	41	Link to PR or Patch
adsclient	ACCEPTED	24	Link to PR or Patch
kanboxwp	ACCEPTED	2	Link to PR or Patch
trellow	ACCEPTED	4	Link to PR or Patch
Bankr	ACCEPTED	1	Link to PR or Patch
32feet	ACCEPTED	3	Link to PR or Patch
wpnest	ACCEPTED	17	Link to PR or Patch
Kinvey-WindowsPhone8	ACCEPTED	7	Link to PR or Patch

What people say

These are what people say about the paper or the transformations of the toolkit when they accept our patches.

I'm very impressed at your work in analyzing the problems empirically and providing tooling to help! Don Syme, Designer&Architect of the F# programming language

That was pretty good, thanks. I'll look forward to the release of that refactoring tool, it seems to be really useful. Guillermo, Developer of Ocell

You are doing very interesting stuff. That's fortunate, because I've been thinking about replacing all asynchronous calls to new async/await style code Vitaliy Soubbotskyy, Developer of phoneguitartab

This is awesome insight! Great work! Tiangong You, Developer of indulged-flickr

That's very interesting and useful. Peter Freeman Foot, Developer of 32feet

That you have pointed out is correct. This time, performance has been improved to 28 milliseconds from 49 milliseconds. Kenji Wada, Developer of Softbuild.Data

Totally agree, I normally try to take the same minimizing approach, though it seems I missed these. Thanks! Pedro Lamas, Developer of Cimbalino-Phone-Toolkit

Team

This is a joint work with University of Illinois at Urbana-Champaign, Delft University of Technology, and Oregon State University.

Semih Okur

PhD Student
University of Illinois

David Hartveld

MSc Student
Delft University of Technology

Danny Dig

Assistant Professor
Oregon State University

Arie van Deursen

Professor
Delft University of Technology