Async CTP v3 - Form is not responding

Question

Hi all,

I played around with the new Async CTP v3 and try to list all files and its subdirectories asyncronously and show this progress by using a progress bar.

Most of the code works fine, but just in the moment I list all entries my Windows form is not responding. What I'm doing wrong?

Below my source code:

Greetings

Peter

Imports System.IO
Imports System.Threading
Imports System.Threading.Tasks
Imports System.Collections.ObjectModel
Imports System.Net

Public Class Form1

    Private Async Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click

        'Clear all entries
        Me.ProgressBar1.Value = 0
        Me.ListBox1.Items.Clear()

        'Define progress
        Dim progress As New Progress(Of NumberEntries)

        'Define ProgressBar
        Me.ProgressBar1.Minimum = 0
        Me.ProgressBar1.Maximum = 100

        'Handler
        AddHandler progress.ProgressChanged, AddressOf ShowProgress

        'Call
        Await TaskEx.Run(Function() Auflistung("C:\windows", progress))

    End Sub

    Public Shared Function Auflistung(ByVal dir As String, ByVal progress As IProgress(Of NumberEntries)) As Task(Of String())

        Dim Direc As New DirectoryInfo(dir)
        Dim Files() As FileInfo
        Dim I As Long = 0

        Files = Direc.GetFiles("*.*", SearchOption.AllDirectories)

        For I = 0 To Files.GetUpperBound(0) - 1

            progress.Report(New NumberEntries With {.Count = (I / Files.GetUpperBound(0)), .Eintrag = Files(I).ToString})

        Next

    End Function

    Public Class NumberEntries

        Public Count As Long
        Public Eintrag As String

    End Class

    Public Sub ShowProgress(source As Object, e As Object)

        Me.ProgressBar1.Value = e.Count * 100
        Me.ListBox1.Items.Add(e.eintrag)

    End Sub

End Class

Answer 1

The reason your form is going (temporarily) unresponsive is because DirectoryInfo.GetFiles does all of the asynchronous work, and then you're doing all of the progress updates all at once. So your UI thread is flooded with updates.

I recommend using DirectoryInfo.EnumerateFiles.

P.S. Read through the Task-based Asynchronous Pattern document - it's in your VS Async CTP install directory under My Documents. It explains how to pattern your asynchronous methods so that they follow best practices and are unsurprising to other programmers.

        -Steve

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Answer 2

Hi Steve,

thanks for your hint! Now my Windows form is still responding while all files are listed.  Below the whole source code including the changes.

Merry Christmas,

Peter

 

Imports System.IO
Imports System.Threading
Imports System.Threading.Tasks
Imports System.Collections.ObjectModel
Imports System.Net

Public Class Form1

    Private Async Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click

        'Clear all entries
        Me.ProgressBar1.Value = 0
        Me.ListBox1.Items.Clear()

        'Define progress
        Dim progress As New Progress(Of NumberEntries)

        'Define ProgressBar
        Me.ProgressBar1.Minimum = 0
        Me.ProgressBar1.Maximum = 100

        'Handler
        AddHandler progress.ProgressChanged, AddressOf ShowProgress

        'Call
        Await TaskEx.Run(Function() ListInfos("C:\windows", progress))

    End Sub

    Public Shared Function ListInfos(ByVal dir As String, ByVal progress As IProgress(Of NumberEntries)) As Task(Of String())

        Dim Direc As New DirectoryInfo(dir)
        Dim I As Long = 0

        ' LINQ query for all files
        Dim files = From f In Direc.EnumerateFiles("*.*", SearchOption.TopDirectoryOnly)

        ' Show results
        For Each f As FileInfo In files

            I += 1
            progress.Report(New NumberEntries With {.Count = (I / files.Count), .Eintrag = f.ToString})

        Next

    End Function

    Public Class NumberEntries

        Public Count As Long
        Public Eintrag As String

    End Class

    Public Sub ShowProgress(source As Object, e As Object)

        Me.ProgressBar1.Value = e.Count * 100
        Me.ListBox1.Items.Add(e.eintrag)

    End Sub

End Class