BeginOutputReadLine not resuming reading lines after process restart

I have an application where I'd like to have the user start over and over a console application ans watch its output redirected in the GUI.
I have noticed that BeginOutputReadLine will correctly get the stdout redirected on the process 1st execution, but will resume reading lines after the process is restarted.

I have managed to reproduce on a small example which as a console application starts a built-in operating system app, which is:

Public Class Form1
    Private firsttime As Boolean
    Private Shared numOutputLines As Integer = 0
    Private filetostart As String

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        filetostart = "c:\windows\system32\ipconfig.exe"
        firsttime = True
    End Sub

    Private Sub calcola()
        If (My.Computer.FileSystem.FileExists(filetostart)) Then

            If (firsttime) Then
                Dim value As ProcessStartInfo
                value = New ProcessStartInfo
                value.FileName = filetostart
                value.CreateNoWindow = True
                value.RedirectStandardOutput = True
                value.WindowStyle = ProcessWindowStyle.Hidden
                value.UseShellExecute = False
                Process1.StartInfo = value
                Process1.EnableRaisingEvents = True
                value = Nothing
                firsttime = False
                AddHandler Process1.OutputDataReceived, AddressOf Process1_OutputDataReceived
                AddHandler Process1.Exited, AddressOf Process1_Exited
                AddHandler Process1.Disposed, AddressOf Process1_Disposed
            End If

            Process1.Start()
            numOutputLines = 0
            Me.TextBox1.Text = "Process started "
            Process1.BeginOutputReadLine()
        Else
            MsgBox("File """ & filetostart & """ does not exist !", MsgBoxStyle.Exclamation, "File not found")
        End If
    End Sub
    Private Sub fine()
        Process1.CancelOutputRead()
        Process1.Close()
    End Sub
    Private Sub Process1_Disposed(ByVal sender As Object, ByVal e As System.EventArgs) Handles Process1.Disposed
        Call fine()
    End Sub
    Private Sub Process1_Exited(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Process1.Exited
        Call fine()
    End Sub

    Private Sub Process1_OutputDataReceived(ByVal sender As Object, ByVal e As System.Diagnostics.DataReceivedEventArgs) Handles Process1.OutputDataReceived
        If Not String.IsNullOrEmpty(e.Data) Then
            numOutputLines += 1
            Me.TextBox1.AppendText(Environment.NewLine + "[" _
                         + Format(numOutputLines, "0000") + "] - " _
                         + e.Data)
        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        calcola()
    End Sub
End Class

So I am posting this here in case anybody has seen this before and before reporting it as a bug.

Paolo

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BeginOutputReadLine not resuming reading lines after process restart

Greg3055

I'm getting threading errors due to having different version of Visual studio.

However, looking at the code, i think if you try this layout it should work ok.

        If (My.Computer.FileSystem.FileExists(filetostart)) Then
            Dim value As ProcessStartInfo = New ProcessStartInfo
            With value
                .FileName = filetostart
                .CreateNoWindow = True
                .RedirectStandardOutput = True
                .WindowStyle = ProcessWindowStyle.Hidden
                .UseShellExecute = False
            End With

            With Process1
                .StartInfo = value
                .EnableRaisingEvents = True
                If (firsttime) Then
                    firsttime = False
                    AddHandler .OutputDataReceived, AddressOf Process1_OutputDataReceived
                    AddHandler .Exited, AddressOf Process1_Exited
                    AddHandler .Disposed, AddressOf Process1_Disposed
                End If
                .Start()
            End With

            numOutputLines = 0
            Me.TextBox1.Text = "Process started "
            Process1.BeginOutputReadLine()
        Else
            MsgBox("File """ & filetostart & """ does not exist !", MsgBoxStyle.Exclamation, "File not found")
        End If

Hope this helps,

Dustin.

doubletree
Of course I meant "I have noticed that BeginOutputReadLine will correctly get the stdout redirected on the process 1st execution, but will NOT resume reading lines after the process is restarted."
BeginOutputReadLine not resuming reading lines after process restart

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BeginOutputReadLine not resuming reading lines after process restart

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BeginOutputReadLine not resuming reading lines after process restart

BeginOutputReadLine not resuming reading lines after process restart

Greg3055

doubletree