The proc.start() hang and unable to close

Question

The code below is unable to exit and hang the application. After pxx_gen.exe is executed, it will request the user to input 8-digit number then it complete. I'm trying to fix it but still no help, don't know what went wrong.

Dim SerNum_Path As String = "C:\Honey\plx_gen.exe"

Private Sub btnProgram_SerNum_Click(sender As Object, e As EventArgs) Handles btnProgram_SerNum.Click
        Dim reader As StreamReader
        Dim outline As String
        Dim failflag As String = Nothing

        lblProgramming_Status.Text = String.Empty
        lblProgramming_Status.Text = "Generate..."
        
        reader = Program_the_Number("cmd.exe", "plx_gen.exe", SerNum_Path, tbxNumber.Text.Trim)

        While Not reader.EndOfStream
            outline = reader.ReadLine()
            rtbProgramming_Console.AppendText(outline & vbCrLf)
            Console.WriteLine(outline)

            If outline.Length > 8 Then

                If outline.IndexOf("file open hb_b0_sn.bin") <> -1 Then
                    failflag = reader.ReadLine()
                    rtbProgramming_Console.AppendText(failflag & vbCrLf)
                End If

            End If
        End While

        If failflag <> ("file open hb_b0_sn_new.bin") Then

            lblProgramming_Status.Text = String.Empty
            lblProgramming_Status.Text = "Fail"
            Return

        End If

        lblProgramming_Status.Text = String.Empty
        lblProgramming_Status.Text = "Generate Done"

    End Sub

Public Function Program_the_Number(ByVal programName As String, ByVal cmdString As String, ByVal programPath As String, ByVal SNumber As String) As StreamReader         
Dim proc As System.Diagnostics.Process = New System.Diagnostics.Process()                  proc.StartInfo.CreateNoWindow = True         
proc.StartInfo.FileName = programName         
proc.StartInfo.UseShellExecute = False         
proc.StartInfo.RedirectStandardError = True         
proc.StartInfo.RedirectStandardInput = True         
proc.StartInfo.RedirectStandardOutput = True         
proc.Start()      
    
If programPath.Length > 17 Then             
proc.StandardInput.WriteLine(programPath(0).ToString() & ":")              
If cmdString.Length <> 0 Then                 
proc.StandardInput.WriteLine("cd " & programPath.Substring(0, (programPath.Length - 17)))                    End If         
End If     
     
proc.StandardInput.WriteLine(cmdString)         
proc.StandardInput.WriteLine(SNumber)         
proc.StandardInput.WriteLine("exit")         
Dim reader As StreamReader = proc.StandardOutput         
proc.Close()         
Return reader      
End Function

Answer 1

Hi @Eekhay ,

Try using Process.WaitForExit Method to make sure that the external process finishes execution before proceeding further in your code.

Also please check Process.StandardError Property.

Synchronous read operations introduce a dependency between the caller reading from the StandardError stream and the child process writing to that stream. These dependencies can result in deadlock conditions.

Best Regards.

Jiachen Li

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