async and await keywords behaviour

Question

1.00/5 (1 vote)

See more:

class AsyncAndAwaitProgram
{
static void Main(string[] args)
{
Method1();
Console.Read();
}
private static async void Method1()
{
await Task.Run(new Action(Method2));
Console.WriteLine("Method 1");
}
private static async void Method2()
{
await task.Run(new Action(Method3));
Console.WriteLine("Method 2");
}
private static void Method3()
{
Console.WriteLine("Method 3");
}
}

I'm expecting output as
Method 3
Method 2
Method 1

Posted 26-Jun-14 8:16am

Sandeep Reddy Badikolu

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard Deeming · Answer 1 · 2014-06-26T08:36:00

You might be expecting that output, but it's not what you're going to get.

Method2 starts a new Task and immediately returns control to the caller. Since it returns void, there is no way for the caller to know when the async method has really completed.

Method1 creates a new task which will be completed when Method2 returns, and then awaits that Task. Since Method2 returns before Method3 has been executed, this Task will complete immediately, and Method1 will continue executing.

async void should only ever be used for top-level event handlers or fire-and-forget methods.

http://channel9.msdn.com/Series/Three-Essential-Tips-for-Async/Tip-1-Async-void-is-for-top-level-event-handlers-only[^]
http://blogs.msdn.com/b/pfxteam/archive/2012/02/08/10265476.aspx[^]

Change your async methods to return a Task instead:

C#

static void Main(string[] args)
{
    Method1().Wait();
    Console.Read();
}

private static async Task Method1()
{
    await Method2();
    Console.WriteLine("Method 1");
}

private static async Task Method2()
{
    await Task.Run(new Action(Method3));
    Console.WriteLine("Method 2");
}

private static void Method3()
{
    Console.WriteLine("Method 3");
}