Async and Await, why two return values - vb.net

Question

I'm trying to get my head around Async and Await. It's going well but one thing I would like clarification on is why there are two return statements in my method. I'm really looking for an explanation of what is actually happening behind the scenes.
I'll post the full code below as it only amounts to around 80 lines. I'm talking about the central method AllSubfolderFiles, which has both Return counter and Return dirsFraction. What's actually happening with these?
Basically, it is a WinForm application that iterates all the files of subfolders, updating a ProgressBar for each iterated subfolder.
Imports System.IO
Public Class frmAsyncProgress
Private Sub frmAsyncProgress_Load(sender As Object, e As EventArgs) Handles MyBase.Load
barFileProgress.Minimum = 0
barFileProgress.Maximum = 100
btnCancel.Enabled = False
End Sub
Private Async Sub btnStart_Click(sender As Object, e As EventArgs) Handles btnStart.Click
If String.IsNullOrWhiteSpace(txtPath.Text) Then
MessageBox.Show("Provide a location first.", "Location")
Exit Sub
End If
Dim sLocation As String = txtPath.Text.Trim()
If Not Directory.Exists(sLocation) Then
MessageBox.Show("Directory doesn't exist.", "Location")
Exit Sub
End If
Dim progressIndicator = New Progress(Of Integer)(AddressOf UpdateProgress)
btnStart.Enabled = False
btnCancel.Enabled = True
lblPercent.Text = "0%"
Dim allFiles As Integer = Await AllSubfolderFiles(sLocation, progressIndicator)
Debug.WriteLine(allFiles.ToString()) 'the number of subfolders iterated
btnStart.Enabled = True
btnCancel.Enabled = False
End Sub
Private Async Function AllSubfolderFiles(location As String, progress As IProgress(Of Integer)) As Task(Of Integer)
Dim dirsTotal As Integer = Directory.GetDirectories(location).Length
Dim dirsFraction As Integer = Await Task(Of Integer).Run(Function()
Dim counter As Integer = 0
For Each subDir As String In Directory.GetDirectories(location)
SubfolderFiles(subDir)
counter += 1
If progress IsNot Nothing Then
progress.Report(counter * 100 / dirsTotal)
End If
Next
Return counter
End Function)
Return dirsFraction
End Function
Private Sub UpdateProgress(value As Integer)
barFileProgress.Value = value
lblPercent.Text = (value / 100).ToString("#0.##%")
End Sub
Private Sub SubfolderFiles(location As String)
'source: http://stackoverflow.com/questions/16237291/visual-basic-2010-continue-on-error-unauthorizedaccessexception#answer-16237749
Dim paths = New Queue(Of String)()
Dim fileNames = New List(Of String)()
paths.Enqueue(location)
While paths.Count > 0
Dim sDir = paths.Dequeue()
Try
Dim files = Directory.GetFiles(sDir)
For Each file As String In Directory.GetFiles(sDir)
fileNames.Add(file)
Next
For Each subDir As String In Directory.GetDirectories(sDir)
paths.Enqueue(subDir)
Next
Catch ex As UnauthorizedAccessException
' log the exception or ignore it
Debug.WriteLine("Directory {0} could not be accessed!", sDir)
Catch ex As Exception
' log the exception or ...
Throw
End Try
End While
'could return fileNames collection
End Sub
End Class
My assessment is that counter is returned and then marshalled back onto the UI thread as dirsFraction, but I'm not convinced by my attempted explanation.

Answer 1

Inside your AllSubfolderFiles function you call Task.Run and pass in an anonymous function that returns with Return counter. AllSubfolderFiles awaits the result of that call and then returns with Return dirsFraction.
So, you have 2 returns in the same function because you have an anonymous function inside your original function. You can move that function out to its own named function which will make it clearer that there are 2 different functions here.