Async ProcessBar not working

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CharlesHe-MSFT asked · Feb 25 at 07:55 AM

Async ProcessBar not working

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?

wpf

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Answer 1 · 2020-02-25T08:00:07.347Z

AlexLi-MSFT answered · Feb 25 at 08:00 AM

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.

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