When do we need to use async?

Ami Kar

5y776Learn iOS Programming

When do we need to use async over thread?

4 Replies

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Sachin Singh5y ago
Accepted answer
There are two real world problems
1.Performance
2.UI responsiveness.

when your sole purpose is to make UI responsive then use async await as it doesn't create thread but it uses state machine concept to remember where to resume the task and at the same time let the main thread(UI thread) to move to next task, thus UI is not blocked.

If your sole pupose is performance then threading too is not going to resolve it, cause so called multi threading is not actually parallel.
MultiThreading just uses time slicing and not uses all CPU that you may have , suppose you have 4 cpu then even if you use multi threading the chances are very less that your code will execute on all 4 CPU,
for performance we have Task Paraller library which forces different task to actually run on different cores.
Sachin Singh5y ago
yes
Multi threading is not parallel bold and loud.
it just creates new thread but doesn't use the hardware efficiently. TPL is what you need for real performance.
And for you why you should use async await over threading , it is because if you will have a loop suppose and you are executing a long task inside loop using thread then it will create huge number of threads and thread starvation may come, so be safe use async and await if the only purpose is to achieve non blocking UI.
Ami Kar5y ago
@sachin You said multithreadinng is not parallel what does it mean? And @mangeshwaran I asked why do i use async over threading. So what is your take on this?
Mageshwaran R5y ago
Hi Ami,
Asynchronous programming is very popular with the help of the async and await keywords in C#. When we are dealing with UI and on button click, we use a long running method like reading a large file or something else which will take a long time, in that case, the entire application must wait to complete the whole task. In other words, if any process is blocked in a synchronous application, the entire application gets blocked and our application stops responding until the whole task completes.
Asynchronous programming is very helpful in this condition. By using Asynchronous programming, the Application can continue with the other work that does not depend on the completion of the whole task.
Suppose, we are using two methods as Method1 and Method2 respectively and both the methods are not dependent on each other and Method1 is taking a long time to complete its task. In Synchronous programming, it will execute the first Method1 and it will wait for completion of this method and then it will execute Method2. Thus, it will be a time intensive process even though both the methods are not depending on each other
We can run all the methods parallelly by using the simple thread programming but it will block UI and wait to complete all the tasks. To come out of this problem, we have to write too many codes in traditional programming but if we will simply use the async and await keywords, then we will get the solutions in much less code.

Example:
public class MasterClass
{
    static void Main(string[] args)
    {
        Method1();
        Method2();
        Console.ReadKey();
    }

    public static async Task Method1()
    {
        await Task.Run(() =>
        {
            for (int i = 0; i < 100; i++)
            {
                Console.WriteLine(" Method 1");
            }
        });
    }


    public static void Method2()
    {
        for (int i = 0; i < 25; i++)
        {
            Console.WriteLine(" Method 2");
        }
    }
}