How To Detect Cmd.Exe Is Done Problem

Question

hi guy

I have one problem with my code below which i try to write a code to detect the cmd.exe when i click button to start timer.start() and when cmd.exe is done and close the main windows, i need timer.stop() and show message to me but i try to using many condition is not work. please share me how to do with this problem.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnCovert.Click

    Dim p As Process

    Dim active As Boolean = True

    Timer1.Start()

    p = Process.Start("cmd.exe", "/c ffmpeg.exe -i " & FileName2 & " -c:v libx264 " & "Down\" & FileName1 & ".mp4")

  if p.HasExited then

  Timer1.Stop()
 msgbox("Close")

 end if

end sub

Answer 1

Hello,

Have you tried Process.WaitForExitAsync ?

Example (full source) which I realize is not using the same command as you but the principle is the same and this is async without showing a windows

Public Shared Async Function GetComputerInformationTask() As Task(Of MachineComputerInformation)  
  
    Const fileName = "computerInformation.json"  
  
    If File.Exists(fileName) Then  
        File.Delete(fileName)  
  
    End If  
  
    Dim start = New ProcessStartInfo With {  
                .FileName = "powershell.exe",  
                .RedirectStandardOutput = True,  
                .Arguments = "Get-ComputerInfo | ConvertTo-Json",  
                .CreateNoWindow = True  
            }  
  
    Using process As Process = Process.Start(start)  
  
  
        Using reader = process.StandardOutput  
  
            process.EnableRaisingEvents = True  
  
            Dim fileContents = Await reader.ReadToEndAsync()  
  
            Await File.WriteAllTextAsync(fileName, fileContents)  
            Await process.WaitForExitAsync()  
  
  
            Dim json = Await File.ReadAllTextAsync(fileName)  
  
  
            Return JsonConvert.DeserializeObject(Of MachineComputerInformation)(json)  
  
        End Using  
    End Using  
End Function  

Usage

Private Async Sub ComputerInfoButton_Click(sender As Object, e As EventArgs) Handles ComputerInfoButton.Click  
  
    Dim details = Await Operations.GetComputerInformationTask()  
    PropertyGrid1.SelectedObject = details  
  
End Sub  

---

Answer 2

hi Karen

i used to use the Process.WaitForExitAsync but seem it not working as what i need because i dont know or estimate with time which FFEMEG will finish convert .mp4 done that is reason why i need using support about it .

Answer 3

hi Mrs. karenpayneoregon

Thanks with your help to recommend me using " Process.WaitForExitAsync " but the problem for my coding is using VB.net not C#, because i dont know how to use C# language. i have try to use vb.net as this coding below it still meet some problem, can't move the form while i click button convert processing. i dont know reason why, so if you can help correct this code for me.

Blockquote

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnCovert.Click

    btnCovert.Enabled = False
    Dim FileName1 As String = System.IO.Path.GetFileNameWithoutExtension(OpenFileDialog1.FileName) 'Get only Flie name without extension
    Dim FileName2 As String = OpenFileDialog1.FileName
    Dim programName As String = "ffmpeg.exe"
    System.Diagnostics.Process.Start(Application.StartupPath & "\" & programName)

    Dim active As Boolean = True
    Dim ts As TimeSpan
    Dim process As Process
    Dim sw As New Stopwatch
    AMins = 0
    ASecond = 0
    sw.Start()
    process = Process.Start("cmd.exe", "/c ffmpeg.exe -i " & FileName2 & " -c:v libx264 " & "Down\" & FileName1 & ".mp4")
    process.WaitForExit()
    sw.Stop()
    If process.HasExited Then
        OutFileInfor()
    End If
    ts = sw.Elapsed
    ' Format and display the TimeSpan value.
    Dim elapsedTime As String = String.Format("Spend Time: {0:00}:{1:00}:{2:00}.{3:00}", ts.Hours, ts.Minutes, ts.Seconds, ts.Milliseconds / 10)
    lbTime.Text = elapsedTime

End Sub

Answer 4

The reason why your form is not responsive is because process.WaitForExit() prevents this. You need to use Await process.WaitForExitAsync() or Await process.WaitForExitAsync(cts.Token) as mentioned in my former reply. Here is what I'm talking about

Public Shared Async Function GetComputerInformationTask(cts As CancellationTokenSource) As Task(Of MachineComputerInformation)

    Const fileName = "computerInformation.json"

    If File.Exists(fileName) Then
        File.Delete(fileName)

    End If

    Dim start = New ProcessStartInfo With {
                .FileName = "powershell.exe",
                .RedirectStandardOutput = True,
                .Arguments = "Get-ComputerInfo | ConvertTo-Json",
                .CreateNoWindow = True
            }

    Using process As Process = Process.Start(start)


        Using reader = process.StandardOutput

            process.EnableRaisingEvents = True

            Dim fileContents = Await reader.ReadToEndAsync()

            Await File.WriteAllTextAsync(fileName, fileContents)

            StopWatcher.Instance.Start()

            Await process.WaitForExitAsync(cts.Token)

            StopWatcher.Instance.Stop()

            RaiseEvent FinishedEvent(StopWatcher.Instance.ElapsedFormatted)


            Dim json = Await File.ReadAllTextAsync(fileName)

            Return JSonHelper.DeserializeObject(Of MachineComputerInformation)(json)

        End Using
    End Using
End Function

Calling the above

Private Async Sub ComputerInfoButton_Click(sender As Object, e As EventArgs) Handles ComputerInfoButton.Click

    TimeLabel.Text = ""

    If PropertyGrid1.SelectedObject IsNot Nothing Then
        PropertyGrid1.SelectedObject = Nothing
    End If

    Dim cancellationTokenSource As New CancellationTokenSource(TimeSpan.FromSeconds(2))

    Dim details = Await Operations.GetComputerInformationTask(cancellationTokenSource)

    PropertyGrid1.SelectedObject = details
    PropertyGrid1.CollapseAllGridItems()

End Sub

Full source

If you don't following the above flow then your form will remain unresponsive.