Microsoft
introduced Async and Await keyword with .Net framework 4.5. Async and Await
keyword can be used to improve your application’s overall responsiveness by
using asynchronous programming. Asynchronous programming is essential when your
application is doing some activity which makes UI unresponsive. You can move
that activity to execute asynchronously so it doesn’t block UI and your application will be
responsive.
You should
consider using Async and Await when you want to keep your application
responsive. Async method provides easier way to do long running work in
background without blocking thread. Ideally method is decorated with Async
keyword should contain one await statement. If you don’t write await statement
in Async method, it won’t give compile error but execute as synchronous method.
Below are few things to remember about Async and Await method.
- The method should contain async modifier.
- Async method return type should be
- Task
- Task<T>
- Void
- The method usually includes at least one await expression.
Let’s have
a look on below example.
Code –
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
public async void DoSum(int number)
{
Console.WriteLine("Task started");
var result = Calculate(number);
Console.WriteLine("Task completed");
if (!result.IsCompleted)
await result;
Answer.Text = result.Result.ToString();
Console.WriteLine(string.Format("Answer is {0}", result.Result.ToString()));
}
public async Task<int> Calculate(int number)
{
var sum = 0;
Task myTask = new Task(() =>
{
for (int i = 1; i
<= number; i++)
{
System.Threading.Thread.Sleep(1000);
sum += i;
}
});
myTask.Start();
await myTask;
return sum;
}
private void
Button_Click(object sender, RoutedEventArgs e)
{
if (!string.IsNullOrEmpty(Input.Text))
{
Console.WriteLine("Sum process started");
var number = Convert.ToInt32(Input.Text);
DoSum(number);
Console.WriteLine("Sum process completed");
}
}
}
Output –
Sum
process started
Task started
Task
completed
Sum
process completed
Answer is 55
As you can
see in output, the UI doesn’t block and cursor immediately return to UI. The sum is calculated and updated asynchronously after all execution completed.
Now let’s
make little change to this programme and use Task.Wait() method to complete task instead
of await. I added myTask.wait() instead of await myTask.
public async Task<int> Calculate(int number)
{
var sum = 0;
Task myTask = new Task(() =>
{
for (int i = 1; i
<= number; i++)
{
System.Threading.Thread.Sleep(1000);
sum += i;
}
});
myTask.Start();
myTask.Wait();
return sum;
}
Output –
Sum
process started
Task
started
Task
completed
Answer is 55
Sum process completed
As you can
see in output, till the sum is calculated UI is blocked and after that sum process is completed. That means myTask.wait() blocks the thread until task completed.
Difference between await and task.wait() -
Task.wait
blocks the thread and await doesn’t block thread and UI.
I hope this
article helps you to know more about async and await. Please leave your
feedback in comments below.
You can download full code from Gist.
See also
–
