Question

I am developing a C# Winforms application, part of the application will be uploading files to a webserver using AsyncUpload (using it,due to the need to use a porgress callback) , In the C# program

i got a simple for loop that calls The Uploading function

 for(int i=0;i < 10 ; i++)
{
  Uploadfun();
}

And the fun does some magic:

Uploadfun()
  { 
  // Logic comes here

   // webClient.UploadFileAsync runs a 2nd thread to perform upload .. 
   webClient.UploadFileAsync(uri, "PUT", fileNameOnHD);  

 }

And a callback that gets called when the Async upload is done

Upload_Completed_callback()
{
  //Callback event
}

Edit

The logic sequence:

1. Fun gets called (from loop)
2. Fun logic is executed and done..
3. Goes back to for loop
4. Callback will be called eventually, when UploadFileAsync (which is running some logic in another thread) will end

The problem is on the 3rd point, when the execution moves back to the for loop, i need to block the loop from continuing until the callback get called.

Answer 1

So if I understand correctly, you want to call UploadFileAsync then block until the async call has hit your callback. If so, I’d use AutoResetEvent i.e

private readonly AutoResetEvent _signal = new AutoResetEvent(false); 

fun()
  { 
  // Logic comes here

   // runs a 2nd thread to perform upload .. calling "callback()" when done
   webClient.UploadFileAsync(uri, "PUT", fileNameOnHD);  

   _signal.WaitOne();   // wait for the async call to complete and hit the callback     
 }



callback()
 {
   //Callback event
   _signal.Set(); // signal that the async upload completed
 }

Using AutoResetEvent means that the state gets automatically reset after Set has been called and a waiting thread receives the signal via WaitOne