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‫Welcome back.

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‫In the last video, you saw how to use threads and how you can set up threats and simply start them.

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‫And in this video, we are going to have a look at completion.

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‫So we want to use a thread to do something and only if a specific task is done, then we want to go

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‫ahead.

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‫So let's have a look at that.

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‫I will create a new variable called task completion source and therefore I need new task completion

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‫source and a boolean.

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‫So as you can see, it's complaining because it doesn't know what this task completion source is.

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‫And in order to fix it I need to use sys threading tasks.

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‫So I'm going to do that for a second.

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‫And then here.

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‫What I'm going to do next is I'm just going to create a test variable.

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‫I'm just going to call a task, which is a task completion source, or we just call this task completion

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‫source.

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‫And we set its task to the result.

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‫So we want to have the result of that task.

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‫So let's say there was a specific task that should run and do something, and then we want to see the

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‫result.

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‫So if it worked out or it didn't work out and to test that, I'm going to get rid of this red line here.

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‫So I'm just going to run the code as if there is nothing else in this main method, only this code here.

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‫So I'm going to run it.

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‫And as you can see, nothing happens.

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‫So the console is kept alive or open, even though we don't have this console red line, which we usually

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‫always use if we want to keep the console open, that means that there is something that is not finished.

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‫So this here is never actually finished because there is no result.

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‫So this completion source is never actually complete, so it's never set to true.

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‫And that's something that we can do manually.

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‫So let's say we have a task and we want to have the result as we have it here, but we actually want

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‫to finish that task at one point.

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‫So what do we need to do for that is to create a thread.

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‫So I'm going to create a var thread

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‫is equal to new thread and that thread will not be started straight away.

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‫So I'm using a little different approach than we did here.

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‫So here we just said new thread and then we had the body of the thread.

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‫So to code that should be executed whenever this thread is initiated and we initiated straight away,

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‫we started straight away.

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‫But here we only create the thread and we can do stuff with it later on.

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‫So here I'm just going to say thread sleep.

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‫So just sleep for let's say 1000 milliseconds and afterwards try to set that task completion source

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‫to true so tri set result.

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‫What that will do is attempt to transition the underlying task into the task status ran to completion

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‫state, which means it's done right so it's going to try to set its done to true.

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‫So that means that this task completion source will be set to true.

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‫And only then we will get this VAR, which is the result of that task.

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‫So let's create a little.

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‫Step in here.

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‫So debug step and let's check the thread IDs.

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‫And now in order to start the thread we actually need to call thread start.

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‫And as you can see this thread object here which is a thread which will do all of that is going to be

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‫started.

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‫So I'm going to start the thread like this and while we're at it, let's have a look at what thread

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‫has to offer.

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‫So whenever you create a thread object, there are multiple properties and methods to use.

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‫Or we can use multiple ones here.

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‫So you can see a board is one where you can abort the thread so you can stop the thread, but that will

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‫run an exception or it will cause an exception.

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‫So that's very dangerous to do actually.

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‫So you can crash your application with that based on how security have built it.

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‫But a board is something that you can of course use to stop a thread, but you never know how far it

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‫is in its execution.

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‫So it can happen that it is not done with the tasks that you wanted to be done with and that will cause

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‫to, well, your program not working correctly.

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‫And then of course, there are plenty of other methods that are pretty interesting like or properties

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‫like this is alive, which means it's this thread currently alive then is background, which means we

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‫can say that a thread should run in the background and we can check with this property.

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‫Whether it's in background or not is a threat to thread.

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‫That's something that we will check out later on.

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‫So what is a thread pool?

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‫That's what we'll see later on and so forth.

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‫So the managed thread ID is something that is pretty interesting, which will tell us about the ID of

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‫the thread that we are currently running.

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‫So let's use that, let's print that onto the console.

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‫So see W and I'm going to use the thread number as this.

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‫So you use the dollar sign and then you have the thread number or thread ID and so you can call it.

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‫And then in curly brackets you use the thread managed ID, so.

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‫Thread managed thread ID.

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‫And of course you need to close the string.

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‫All right, now let's test it.

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‫Let's run the code.

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‫And we are we have our main thread.

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‫And so far we have something on the console.

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‫As you can see, thread number is three.

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‫So the number of this thread that we have here that we've created ourselves is actually three and the

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‫main thread it's managed ID is one.

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‫So as you can see, the numbers don't actually have to be in the manner that you would expect them.

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‫So even though we haven't created our own additional thread in here, it goes from 1 to 3.

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‫So there have to be other threads that are running that we don't see here.

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‫All right.

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‫And by the way, if you want to see whether a thread has started and end it, you can do the following.

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‫So.

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‫So let's cut that here and put it in this line here.

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‫And actually, let's say started and here.

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‫We cannot use thread because thread is this thread that we create here.

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‫But if we want to use it in here within the thread body itself, then we need to use thread dot current

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‫thread.

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‫So if we do that now, we will have the thread that we are currently in, which is exactly that.

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‫And here we say it started and after it's done we say it's ended.

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‫And now let's run it.

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‫It's run the code.

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‫And as you can see, nothing is displayed on the console.

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‫Let's go to the next step.

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‫And then it started and ended.

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‫So it happened quite quickly.

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‫But as you can see, there are.

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‫So let's give it a little more time.

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‫Let's change it to 5 seconds.

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‫And let's also get rid of this debug point here and let's run it.

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‫So thread number three started and then it took a while and it went to finished.

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‫So now you see that this line of code is actually executed correctly and it simply stops our console.

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‫So let's get the console read line to keep the console open.

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‫So thread number three started and then 5 seconds later it should end so that we are thread number three

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‫ended.

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‫Now let's say we want to see the task actually worked out.

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‫So if it worked out to set it to true or not.

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‫Well, we know because otherwise we wouldn't get to the next step.

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‫But let's use console right line in here.

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‫Task was done and here I'm just going to write the result which will be test.

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‫So test is just a bowl, as you can see here, because either it worked or it didn't work.

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‫So we sell this either true or false.

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‫So let's check it out.

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‫And now we need to wait for 5 seconds.

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‫Number three started 5 seconds and then number three ended and it says task was done is equal to true.

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‫So that's what's happening here with this line.

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‫So it simply says it's done with this specific task.

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‫All right.

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‫So in this video, you saw how you can use the task completion source, which indicates whether a task

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‫is done or not.

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‫You can set it to true or it can simply do something and be done.

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‫After a while, you also saw that you can create a thread in a different manner, so you can actually

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‫create a thread variable, which you then have to start of course, and you can simply use like an object

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‫of the class thread.

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‫And then we saw how we can use the manage thread ID so we know the ID of that specific thread.

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‫And that's something that we'll look into a little more in the next video where we create multiple threads

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‫at the same time and then we will see how it's going to be handled by our machine.

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‫So see you in the next video.