How to correctly write async method

Question

So I am trying to learn the basics of using  async  and  await  in C   but I am not sure what I am doing wrong here  I am expecting the following output   Calling DoDownload DoDownload done     output here       But I don t get the output of the download  and I also expect  done  but that takes a while  Shouldn t that be output immediately  Also  I can t seem to get the string result either  Here is my code   namespace AsyncTest       class Program               static void Main string   args                        Debug WriteLine  Calling DoDownload                DoDownloadAsync                Debug WriteLine  DoDownload done                       private static async void DoDownloadAsync                         WebClient w   new WebClient                 string txt   await w DownloadStringTaskAsync  http   www google com                 Debug WriteLine txt

User · Accepted Answer

To get the behavior you want you need to wait for the process to finish before you exit Main(). To be able to tell when your process is done you need to return a Task instead of a void from your function, you should never return void from a async function unless you are working with events.

A re-written version of your program that works correctly would be

class Program {     static void Main(string[] args)     {         Debug.WriteLine("Calling DoDownload");         var downloadTask = DoDownloadAsync();         Debug.WriteLine("DoDownload done");         downloadTask.Wait(); //Waits for the background task to complete before finishing.      }      private static async Task DoDownloadAsync()     {         WebClient w = new WebClient();          string txt = await w.DownloadStringTaskAsync("http://www.google.com/");         Debug.WriteLine(txt);     } }

Because you can not await in Main() I had to do the Wait() function instead. If this was a application that had a SynchronizationContext I would do await downloadTask; instead and make the function this was being called from async.

User · Answer

You are calling DoDownloadAsync   but you don t wait it  So your program going to the next line  But there is another problem  Async methods should return Task or Task lt T gt   if you return nothing and you want your method will be run asyncronously you should define your method like this   private static async Task DoDownloadAsync                 WebClient w   new WebClient             string txt   await w DownloadStringTaskAsync  http   www google com             Debug WriteLine txt           And in Main method you can t await for DoDownloadAsync  because you can t use await keyword in non-async function  and you can t make Main async  So consider this   var result   DoDownloadAsync     Debug WriteLine  DoDownload done    result Wait

[c#] How to correctly write async method?

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