Wait till task returns

Question

How do i wait my method for a task to complete before the method returns.

public async void  barcodescanner()
{
    var scanner = new ZXing.Mobile.MobileBarcodeScanner();
    barcode =  await scanner.Scan();
}   

Definition of scaner.Scan():

public Task<Result> Scan();

Answer 1

You can't wait for result of async void method - it is explicitly "fire and forget" behavior.

If you want to wait for completion - return Task and .Wait on it

public async Task  barcodescanner() {...}

barcodescanner().Wait(); 

Notes:

• synchronously waiting for async methods can cause deadlocks and in general not recommended - so do it on your own risk. See await vs Task.Wait - Deadlock? for details
• Difference between void and Task return covered in What's the difference between returning void and returning a Task? answer.

Answer 2

You could always do this:

public void barcodescanner()
{
    var scanner = new ZXing.Mobile.MobileBarcodeScanner();
    barcode =  scanner.Scan().Result;
}