Async ProcessBar not working

Question

Source thread: Async ProgressBar not working, answered by Peter Fleischer.

I'm trying to set up an async read of a bunch of files with a ProgressBar, but it doesn't work.

Here is my MainWindow:
Class MainWindow
Dim TheProgress As Progress(Of Integer)
Dim ProgCntr As Integer
Dim CToken As CancellationToken

And the process code:

Public Async Sub StartFntRead(TheFiles As List(Of IO.FileInfo), TheTxt As String)   
        With Me  
            .ProgBar.Value = 0  
            .ProgBar.Maximum = TheFiles.Count  
            .ProgBar.Visibility = Windows.Visibility.Visible  
        End With  
        With Me.LablProgText  
            .Content = TheTxt  
            .Visibility = Windows.Visibility.Visible  
        End With  
        ProgCntr = 0  
        CToken = New CancellationToken  
        TheProgress = New Progress(Of Integer)(AddressOf ReportProgress)  
        Await ReadFntFiles(CToken, TheFiles, TheProgress)  
        Me.ProgBar.Visibility = Windows.Visibility.Hidden  
        Me.LablProgText.Visibility = Windows.Visibility.Hidden  
    End Sub  
  
    Public Async Function ReadFntFiles(CTokn As CancellationToken, TheFiles As List(Of IO.FileInfo), Prog As IProgress(Of Integer)) As Task(Of Integer)  
        Dim Fnt As FntData  
        For Each AFile In TheFiles  
            ProgCntr += 1  
            Prog.Report(ProgCntr)  
            Fnt = New FontUtils.FntData With {.FName = AFile.FullName}  
            Select Case System.IO.Path.GetExtension(AFile.FullName).ToUpper  
                Case Is = ".TTF", ".OTF"  
                    Call FontUtils.ReadTTOT(Fnt)  
                Case Is = ".PFM"  
                    Call FontUtils.ReadT1(Fnt)  
            End Select  
            If Fnt.IsOK Then  
                TheAvailFnts.Add(Fnt)  
            Else  
                FntErrsSet.Fnts.Add(Fnt)  
            End If  
        Next AFile  
    End Function  
    Public Sub ReportProgress(ByVal ProgNum As Integer)  
        Me.ProgBar.Value = ProgNum  
    End Sub  

To start processing files, call the StartFntRead method:

Call StartFntRead(TheFiles, "Reading font files")  

Any suggestion?

Answer 1

Hi,

Welcome to our Microsoft Q&A platform!

You can try the following demo:

 Imports System.IO  
Imports System.Threading  
  
Public Class Window1  
  
  Private ProgCntr As Integer  
  Private CToken As CancellationTokenSource  
  Private TheProgress As New Progress(Of Integer)  
  
  Private Sub Button_Click(sender As Object, e As RoutedEventArgs)  
    Dim listFI As List(Of FileInfo)  
    listFI = (From item In My.Computer.FileSystem.GetFiles("c:\temp") Select New FileInfo(item)).ToList  
    StartFntRead(listFI, "txt")  
  End Sub  
  
  Public Async Sub StartFntRead(TheFiles As List(Of IO.FileInfo), TheTxt As String)  
    With Me  
      .ProgBar.Value = 0  
      .ProgBar.Maximum = TheFiles.Count  
      .ProgBar.Visibility = Windows.Visibility.Visible  
    End With  
    With Me.LablProgText  
      .Content = TheTxt  
      .Visibility = Windows.Visibility.Visible  
    End With  
    CToken = New CancellationTokenSource()  
    Dim ct As CancellationToken = CToken.Token  
    AddHandler TheProgress.ProgressChanged, Sub(s, n)  
                                              ProgBar.Value = n  
                                            End Sub  
    Await Task.Run(Sub() ReadFntFiles(TheFiles, TheProgress, CToken.Token), CToken.Token)  
    MsgBox("Back after ReadFntFiles")  
    Me.ProgBar.Visibility = Windows.Visibility.Hidden  
    Me.LablProgText.Visibility = Windows.Visibility.Hidden  
  End Sub  
  
  Public Sub ReadFntFiles(TheFiles As List(Of IO.FileInfo), ByVal progress As IProgress(Of Integer), ByVal ct As CancellationToken)  
  
    ' comment out for demo purposes  
  
    'Dim Fnt As FntData  
    '' with following method you can create a async thread and return awaitable object  
    'Dim ProgCntr As Integer = 0  
    'For Each AFile In TheFiles  
    '  If ct.IsCancellationRequested Then Exit For  
    '  ProgCntr += 1  
    '  progress.Report(ProgCntr)  
    '  Fnt = New FontUtils.FntData With {.FName = AFile.FullName}  
    '  Select Case System.IO.Path.GetExtension(AFile.FullName).ToUpper  
    '    Case Is = ".TTF", ".OTF"  
    '      Call FontUtils.ReadTTOT(Fnt)  
    '    Case Is = ".PFM"  
    '      Call FontUtils.ReadT1(Fnt)  
    '  End Select  
    '  If Fnt.IsOK Then  
    '    TheAvailFnts.Add(Fnt)  
    '  Else  
    '    FntErrsSet.Fnts.Add(Fnt)  
    '  End If  
    '  'MsgBox(Fnt.DisplayName)  
    'Next AFile  
  
    ' simalation of work  
    For i = 1 To 100  
      If ct.IsCancellationRequested Then Exit For  
      Thread.Sleep(100) ' simulate working time  
      progress.Report(i)  
    Next  
  
  End Sub  
  
End Class  

Thanks.