Asynchronous Programming in .NET 4.5 (async and await)

[@mikeckennedy]

Hi folks. If you're enjoying this presentation, I also have a 5-hour course in Python covering Python's equivalent async and await as well as more. Check it out at training.talkpython.fm/courses/explore_async_python/async-in-python-with-threading-and-multiprocessing

[@Euquila]

VB programmer here. I just switched from .net 4.0 to 4.5 and wanted to learn about async and await. I found your video exceptional. You really have a knack for teaching!

[@LucasBatistussi]

Wow! This is the best "tutorial" about asynchronous programming I ever saw! Finally I understood what asynchronous tasks are and differences with parallel approach. Keep doing this kind of great work! Congratulations! Favorited.

[@AlanDias17]

Best explanation I've ever found. We admire your work, dedication and competence.

[@mikeckennedy]

Thank you!

[@ValiRossi]

I agree. Good job.

[@magnusdeus123]

Just halfway through your video Michael and have to express my gratitude. You've explained this subject much clearer than so many other instructors whose I've tried to follow; especially even those on some huge, well-funded, training sites. Thank you, particularly, for explaining the little bit about Tasks in the beginning - so many tutorials either seem too dated; keen on teaching C# 3.5 Thread-based programming patterns, or jump straight to async and await.

[@mikeckennedy]

Thanks so much Ash!

[@LouisWaweru]

@@mikeckennedy I agree, I was almost sad to see your more recent videos are on Python 😅

[@mikeckennedy]

@@LouisWaweru thanks for the nice thoughts Louis.

[@MattRothtauscher]

So old but still gold. Thanks for super easy understanding in that topic with going into detail. It really helped me understanding all of it :)

[@mikeckennedy]

+Matt Rothtauscher Thanks, glad it helped you grok it!

[@mikeckennedy]

Yes totally. The same stuff you see here applies. You just cannot touch the UI elements from the background threads so 1. Gather what you need. 2. Kick off the bg work. 3. The async / await keyword should bring you back to the ui thread on completion, then update the UI elements.

[@Fean9rz]

I was having big problems finding a way to fix a bug in my logic. I had a while(true) { // stuff } and other code that had to be executed at the same time. This video with the async await Task.Delay(time), made my day!!! Thank very very much!

[@pavansonty1]

Great video. I went through lot of material/other videos. But couldnt exactly understand how async await works. Thanks a lot for clearing the confusions around async & await.

[@mikeckennedy]

You're welcome. Thanks!

[@dland2000]

Great video. Really helpful. The Surface vs. iPad search was classic.

[@danielschmid8530]

Holy, that's what I call in-depth! I have been using the Thread and ThreadPool classes for a long time now and never really got around looking into that topic more thoroughly, but this has enlightended me so much! Everything is explained to the extent I need to update my applications using the await and async keywords and the Task-class, and get rid of the Thread and ThreadPool classes. Although I will profile the overhead Task has over ThreadPool, just for paranoia reasons. ;) Gonna share this.

[@WoundedEgo]

I went to your website. What a great resource for us developers. Thanks!

[@mikeckennedy]

Hi, Good question. You could use Parallel.ForEach but it would not have exactly the same effect. Using the await keyword on what is ultimately webclient.DownloadStringTaskAsyc() means we are just waiting on IO Completion ports. You'll see that the system doesn't actually create any more threads. ...

[@OtRatsaphong]

Wow, Great tutorial!! I finally understand how to use async & await. Thanks for the clear explanation.

[@UBOATss]

First of all thank you for this information...2nd to sum it all up its like having your software invading multiple cpu's :) with 'continue with' you literally keep feeding the invasion and re-supply with instructions...this is awesome thanks again! i come from multi threading in java...this is very powerful stuff

[@pratapkv2305]

Makes things crystal clear! Thanks Michael.

[@yrajeshk532]

thanks Michael that was good introduction to the Asynchronous programming

[@cvaldivia93]

Excellent video; thanks for sharing. You have a real gift for teaching.

[@michor10]

This was a really well done presentation. Thank you for sharing.

[@KCAbramson]

Thanks for this. Wish i saw it back when it first came out! It's time to take the async thing more seriously like an adult coder.

[@mikeckennedy]

+KC Abramson Thanks so much KC!

[@nfskis]

It's just Amazing. Very easy to understood what I have to study it!. Thanks you so much Michael. I love your video!! BEST C# Video ever!

[@kevinpacheco8169]

This was amazing, thank you so much for putting this up!

[@kirkbae9808]

I agree. Best explanation on this topic. Thank you very much.

[@grog8164]

Hey, great video! I have a question if I may. At 43:05 we see that we are on the main thread with the while true loop. If I understand correctly, because of async/await keyword on Task.Delay it mean that : "during the 200 ms of delay, the code execution is at exterior of the infinite loop, which makes the program not freezing and then (after 200ms) go back to your loop with your conditionnal SearchStats.downloadCount that is executed within few ms." If I remermber correctly you said that the await in from of something could be seems as a "continue" keyword allowing the code to proceed. But why the code goes exterior ?

[@mikeckennedy]

Thanks. Basically, the await delay pushes a callback onto the event loop and then releases the UI thread. So while it looks like it should totally freeze up the program but because it does the callback + releases the thread each time through the loop all is well.

[@mikeckennedy]

Thanks Daniel! You're most welcome. I appreciate the feedback. :)

[@DJDoena]

Question: at 46:45 you can see that your new method has an await in it. Wouldn't that mean that the calling method with the loop would still be waiting for every download to complete before starting the next?

[@mikeckennedy]

Hi DJ, There are two loops. The first foreach loops starts ALL the downloads and adds them to a List. At this point they are all running. The while loop just pulls them out as they finish, but they have all been started prior to hitting the while loop with the await. Make sense?

[@responsibleparty]

Great explanation of these concepts. Of course, the "message pump" version of the multithreading causes some problems that you didn't address. For example, when you click the Search button, it will be possible to click it again while it is running. These are the types of issues I think can be tricky. Clearly, you'd need to prevent that somehow.

[@brakes255]

Thanks Michael, was cool. This is kind of an odd question..is there anyway for components in the WPF framework to work Asynchronously, such as when displaying a treeView that has many nodes attached to it that it will load the nodes one by one onto the screen instead of the entire mainwindow locking until the treeview has finished processing?

[@thebeauti101]

Thank you for a great tutorial Michael!

[@amaterasu48]

This was very informative and easy to understand. Thank you!

[@mikeckennedy]

Hi, are you asking for visual studio theme or for the powerpoint stuff?

[@claudiovalerio7253]

Great video, great features! For decompiling, I suggest "Just Decompile" by Telerik: free, light and it just does the job!

[@mikeckennedy]

If we did a Parallel.ForEach, we'd have a thread tied up for each pending request in addition to just the network wait. So we would add some overhead. It wouldn't be computational overhead in this case, but realize that we are then tied to the thread pool which limits the number of threads (approx 20 / CPU in practice) and each one requires 1 MB stack space. So it'd be similar, but we do get some truly new benefits from this Task.WhenAny version. Cheers, @mkennedy

[@ncaatrackstar]

I loved your tutorial, but why didn't you use the 1st Task example when trying to demonstrate the async and await commands? It would be great to see a 1 to 1 comparison.

[@apraveen25]

Excellent demo. Thank you very much. Can you check the link for demo code as its not working right now?

[@gauravtemkar8524]

Great Video! Thanks for the cool stuff..! :) Keep up the good work

[@K0nc3pt10n]

Excellent video! Very well explained.

[@klue16]

Any plans in the future to continue this tutorial? Maybe covering best practices in a multitude of situations? Dos & don'ts, etc.

[@mikeckennedy]

No immediate plans directly on this series, but we are adding about 6 hours on this to LearningLine: learninglineapp.com/schedule I can let you know when it's ready.

[@klue16]

Michael Kennedy , thank you! Definitely signing up. :-)

[@TheTrueSmitch]

Michael! Wonderful video however I was wondering about a few things. First of all I noticed in your web search example you only used await at the once part. My question for that part was since you only used that would the thread run all the other code besides the await or would it just run it asynchronously but not run other tasks on the same thread.

[@ej2649]

Thank you Michael! Really help! Good tutorial.

[@mikeckennedy]

Sure, see the description of the video.

[@mahensavale]

Great explanation Michael !

[@mikeckennedy]

+Mahendra Savale Thank you!

[@NickMaovich]

Really nice explanations, examples, and code! Thank you a lot!

[@dangnguyenvinhphuoc7206]

Hi Mchael, this is good video to learn about Async and await, I could I have a example code of the second part (download using async). Thanks,

[@mikeckennedy]

Thanks. The only code I have still around is at s3.amazonaws.com/michael-kennedy/blog/asynchronous-programming-in-net-4-5-video/websearcher-final-async-await-kennedy-demo.zip Hope that works!

[@mikeckennedy]

Thank you everyone!

[@arpit280392]

Thanks a lot Micheal...very clear explanation.

[@mikeckennedy]

+Arpit Jain You're welcome!

[@mikeckennedy]

I'd be happy to, however, I'm not sure where it is anymore. :(

[@ChinmayGadre]

very succinct training on async and await!

[@nikitashrivastava8800]

Great work !!! will keep this forever for reference :)

[@mikeckennedy]

+Nikita Shrivastava Thank you so much Nikita!

[@mikeckennedy]

Hi. I didn't do anything special. This is just the theme of Win8 at the time - was running a dev preview of win 8.

[@weima544]

Explained so clearly, thanks

[@klue16]

Awesome tutorial!! Thank you so much; really helpful.

[@mikeckennedy]

Thanks, glad you like it!

[@mikeckennedy]

Thanks Omar. I updated the link in the comments for downloading the code.

[@karenwoods8567]

Hi Mike, where do we download the source code used in this tutorial? Please advise. Thanks..great video btw

[@lynndemarest1902]

One word: Brilliant. Thank you. (OK three words.)

[@mikeckennedy]

Thanks a bunch Lynn. Glad it was helpful. :)

[@mikeckennedy]

Glad you liked it. Great analogy!

[@rmzzz76]

Thank you so much for the information.... While I think the Task functionality added with .NET 4.0 is intuitive and useful, the sync / await syntax and overall paradigm were a poor direction. C# has not aged very well.

[@krishnakantsharma09]

Very nicely explained. Thanks :)

[@a1689k]

The code doesnt work.. The search always returns an empty list, no matter whatever you search, and how much ever you increase the "entire internet".. could be a minor bug in the parallel programming logic.. as I am new to it, cannot fix it.. can anyone help?

[@mikeckennedy]

Hi. I just downloaded the code, recompiled it and ran it. Works fine. Try a common term like truck or something.

[@varshacon]

Hi Michael, could you please paste the link again, I don't find the link anywhere. Thanks.

[@ahmxtb]

Why 48:00 using .ToArray()? I think it's not needed.

[@mikeckennedy]

You're welcome, thanks for saying so.

[@mikeckennedy]

Check the source, just updated the download like to work.

[@nileshdDeolikar]

I want to DataGrid.DataSource = dbcontext.selectcateroties(0, 1).ToList(); in task

[@JoshYates]

Well explained. Thank you sir.

[@mikeckennedy]

Thanks!

[@kllbd]

hey dude, what's this Windows version? :o I was looking for it, but I didn't find the right version.

[@PythonBytes]

Hi. I think that sweet OS is Vista. :) It wasn't that great but was OK. Looked good.

[@vkg.codefactory]

Nice presentation, where can I find the demo source code?

[@vkg.codefactory]

I got it, it is just mentioned in the bottom notes, sorry!

[@JoshYates]

Vinod Kumar Gupta The link was broke. hmmm....unless it's a firewall issue.

[@jayeshmodha]

Thank you sir, you have a great teaching skill

[@IWIH90]

Thank you for the awesome tut.

[@ranjithk842]

Nicely explained!!! Thanks

[@garyngzb]

what theme you use?

[@varshacon]

Link to source code for both projects please.

[@ReductioAdAbsurdum]

This is an interesting talk, but the motivation presented at the start is not relevant (free lunch is over). The `async` keyword doesn't make it any easier to parallelize computation for purposes of increasing CPU utilization on a multi-core machine. It mostly makes it easier to write code that waits on long processes without blocking out main thread, for purposes of app responsiveness.

[@PaulSebastianM]

Windows 8 with non-standard theme? How?

[@ryanjackson0x]

Can you share your slidedeck?

[@NGUY0035]

awesome explaination!

[@mikeckennedy]

Thanks Lucas! Much appreciated.

[@mikeckennedy]

Thanks Cuong!

[@Yartch]

Thanks, great video! This really cleared a lot up for me.

[@ThugLifeModafocah]

The Async vs Parallel (1) is real parallelism. Two or more processing cores taking tasks in parallel. The Async vs Parallel (2) is concurrency. There's no real parallelism, the tasks are processed one at a time, switching very fast, giving the impression of simultaneos processing, but it's not. So async can be either parallel or concurrent and it is a big improviment from serial processing.

[@menakaramasamy8936]

This is amazing video. Thanks a lot.

[@loam]

5:40 - dude foresaw the future, AMD Threadrippers and others really did came out.

[@mikeckennedy]

:)

[@iElite6809]

Great video. You just earned yourself a like and a subscription from me!

[@prosoftwebindia]

Nice! Thank You.

[@jmng9689]

Great work.

[@somnath.sonawne]

Excellent video !!!!!!!!

[@ZackLoveless]

Great video, thanks!

[@mikeckennedy]

Thanks Joe!

[@pr0l0gix]

awesome!! thanks!!

[@milanmladenovic]

Great video! Thanks

[@voodark]

Thank you very much!!

[@mikeckennedy]

Thanks, link updated!

[@cuongdev]

the video's so good, thanks.

[@swoyum]

Informative !

[@KavkkAZEcc]

Thanks for tutorial

[@ipekb3039]

Thank you sir.

[@davidfreire3766]

good work ;)

[@mikeckennedy]

Thanks!

[@dannyc.8696]

bill gates disliked this video at 29:48

[@evyngreenwood6108]

Nah, like always, the only time apple is more useful than windows is when the windows user fucks up.

[@sujithpattambi]

No, he will not :) . It is typo "suface" instead of "surface"

[@gitnomad]

Thanks.