take combo box choice and use choice as SETX

Question

I have the following code to create a combo box that shows a list of ports in use on the PC What I want to do is take the users choice of port and assign it to a system variable using the SETX command. At the moment the user enters the port number manually in a batch file, the aim is to skip this step and replace it with the choice from the combo box

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    myPort = IO.Ports.SerialPort.GetPortNames()
    ComboBox1.Items.AddRange(myPort)

The batch file looks like this at present and works fine

    set /p port= "What is your port number  "
    setx port "%port%"

So is there a way to remove the user having to enter the port number and have the batch file run its script using the choice from the combo box Thanks

Answer 1

According to this post

set modifies the current shell's (the window's) environment values, and the change is available immediately, but it is temporary. The change will not affect other shells that are running, and as soon as you close the shell, the new value is lost until such time as you run set again.

setx modifies the value permanently, which affects all future shells, but does not modify the environment of the shells already running. You have to exit the shell and reopen it before the change will be available, but the value will remain modified until you change it again.

---

For set /p port= "What is your port number: "

one can use the following in VB.NET:

Environment.SetEnvironmentVariable("port", "COM5", EnvironmentVariableTarget.Process)

where "COM5" is your port number (replace this with the value from your ComboBox).

---

For setx port "%port%":

Permanent environment variables are stored in the registry: HKEY_CURRENT_USER\Environment.

To set an environment variable in HKEY_CURRENT_USER\Environment, do one of the following.

Option 1:

'by specifying 'EnvironmentVariableTarget.User', the value will be updated in the registry (HKEY_CURRENT_USER\Environment)
Environment.SetEnvironmentVariable("port", "COM5", EnvironmentVariableTarget.User)

where "COM5" is your port number (replace this with the value from your ComboBox).

Option 2:

Add Imports

• Imports Microsoft.Win32

SetUserEnvironmentVarReg:

Private Sub SetUserEnvironmentVarReg(name As String, val As String, Optional regView As RegistryView = RegistryView.Registry64)
    Using currentUserKey As RegistryKey = RegistryKey.OpenBaseKey(RegistryHive.CurrentUser, regView)
        Using envKey As RegistryKey = currentUserKey.OpenSubKey("Environment", True)
            If envKey IsNot Nothing Then
                'set value
                envKey.SetValue(name, val)
            End If
        End Using
    End Using
End Sub

Usage:

SetUserEnvironmentVarReg("port", "COM5")

where "COM5" is your port number (replace this with the value from your ComboBox).

---

Let's create a test batch script. The test batch script will allow one command-line argument which will allow it to be used with the different options shown below. If a command-line argument is supplied, the batch script will used the specified value, otherwise it will use the value inherited from the environment variable.

TestEnvVar.bat:

@echo off

if not "%1" equ "" (
    set port=%1
)

echo port: %port%

---

One can use System.Diagnostics.Process to run the batch script.

RunProcessInheritEnvironmentVar:

Private Sub RunProcessInheritEnvironmentVar(filename As String, portName As String)

    'set environment variable (process-level)
    Environment.SetEnvironmentVariable("port", portName, EnvironmentVariableTarget.Process)

    'set environment variable (user-level)
    'sets environment variable in HKEY_CURRENT_USER\Environment
    Environment.SetEnvironmentVariable("port", portName, EnvironmentVariableTarget.User)

    Dim startInfo As ProcessStartInfo = New ProcessStartInfo(filename) With {.CreateNoWindow = True, .RedirectStandardError = True, .RedirectStandardOutput = True, .UseShellExecute = False, .WindowStyle = ProcessWindowStyle.Hidden}

    Using p As Process = New Process() With {.EnableRaisingEvents = True, .StartInfo = startInfo}

        AddHandler p.ErrorDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                            If Not String.IsNullOrEmpty(e.Data) Then
                                                'ToDo: add desired code
                                                Debug.WriteLine("error: " & e.Data)
                                            End If
                                        End Sub

        AddHandler p.OutputDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                             If Not String.IsNullOrEmpty(e.Data) Then
                                                 'ToDo: add desired code
                                                 Debug.WriteLine("output: " & e.Data)
                                             End If
                                         End Sub

        p.Start()

        p.BeginErrorReadLine()
        p.BeginOutputReadLine()

        'wait for exit
        p.WaitForExit()

    End Using
End Sub

Usage:

RunProcessInheritEnvironmentVar("C:\Temp\TestEnvVar.bat", "COM5")

where "COM5" is your port number (replace this with the value from your ComboBox).

---

It's not clear whether or not you actually need to set the environment variable permanently (ie: in HKEY_CURRENT_USER\Environment). If the environment variable is only being used for the batch script being executed, one may consider one of the alternate methods shown below.

When using System.Diagnostics.Process an environment variable can be set using ProcessStartInfo.EnvironmentVariables which sets the environment variable within the scope of the System.Diagnostics.Process process. The code below doesn't change the value in the registry.

RunProcessSetEnvironmentVar :

Private Sub RunProcessSetEnvironmentVar(filename As String, portName As String)
    Dim startInfo As ProcessStartInfo = New ProcessStartInfo(filename) With {.CreateNoWindow = True, .RedirectStandardError = True, .RedirectStandardOutput = True, .UseShellExecute = False, .WindowStyle = ProcessWindowStyle.Hidden}

    'add environment variable
    startInfo.Environment.Add("port", portName)

    Using p As Process = New Process() With {.EnableRaisingEvents = True, .StartInfo = startInfo}

        AddHandler p.ErrorDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                            If Not String.IsNullOrEmpty(e.Data) Then
                                                'ToDo: add desired code
                                                Debug.WriteLine("error: " & e.Data)
                                            End If
                                        End Sub

        AddHandler p.OutputDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                             If Not String.IsNullOrEmpty(e.Data) Then
                                                 'ToDo: add desired code
                                                 Debug.WriteLine("output: " & e.Data)
                                             End If
                                         End Sub


        p.Start()

        p.BeginErrorReadLine()
        p.BeginOutputReadLine()

        'wait for exit
        p.WaitForExit()

    End Using
End Sub

Usage:

RunProcessSetEnvironmentVar("C:\Temp\TestEnvVar.bat", "COM5")

where "COM5" is your port number (replace this with the value from your ComboBox).

---

Lastly, let's look at how one could specify the port name as an argument because the test batch script allows command-line arguments. The code below doesn't change the value in the registry.

RunProcessWithArgument:

Private Sub RunProcessWithArgument(filename As String, Optional arguments As String = Nothing)
    Dim startInfo As ProcessStartInfo = New ProcessStartInfo(filename) With {.CreateNoWindow = True, .RedirectStandardError = True, .RedirectStandardOutput = True, .UseShellExecute = False, .WindowStyle = ProcessWindowStyle.Hidden}

    If Not String.IsNullOrEmpty(arguments) Then
        startInfo.Arguments = arguments
    End If

    Using p As Process = New Process() With {.EnableRaisingEvents = True, .StartInfo = startInfo}

        AddHandler p.ErrorDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                            If Not String.IsNullOrEmpty(e.Data) Then
                                                'ToDo: add desired code
                                                Debug.WriteLine("error: " & e.Data)
                                            End If
                                        End Sub

        AddHandler p.OutputDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                             If Not String.IsNullOrEmpty(e.Data) Then
                                                 'ToDo: add desired code
                                                 Debug.WriteLine("output: " & e.Data)
                                             End If
                                         End Sub


        p.Start()

        p.BeginErrorReadLine()
        p.BeginOutputReadLine()

        'wait for exit
        p.WaitForExit()

    End Using
End Sub

Usage

RunProcessWithArgument("C:\Temp\TestEnvVar.bat", "COM5")

where "COM5" is your port number (replace this with the value from your ComboBox).

---

I've shown a variety of methods that can be used to specify an environment variable that can be used for a batch script depending upon your needs. For a slight variation of System.Diagnostics.Process usage see here.

---

Update:

When using System.Diagnostics.Process, one can also use StandardInput to provide value(s) for prompt(s).

TestEnvVar.bat:

@echo off

set /p port= "What is your port number:  "
setx port "%port%"

echo port: %port%

for /f "delims=" %%a in ('^(reg query "HKCU\Environment" /v "port" ^|find /i "port"^)') do (
  echo %%a
)

RunProcessWithStandardInput:

Private Sub RunProcessWithStandardInput(filename As String, portName As String)
    If String.IsNullOrEmpty(filename) Then
        Throw New Exception("Error: 'filename' is null or empty.")
    ElseIf Not System.IO.File.Exists(filename) Then
        Throw New Exception($"Error: '{filename}' could not be found.")
    End If

    If String.IsNullOrEmpty(portName) Then
        Throw New Exception("Error: 'portName' is null or empty.")
    End If

    Dim startInfo As ProcessStartInfo = New ProcessStartInfo(filename) With {.CreateNoWindow = True, .RedirectStandardError = True, .RedirectStandardInput = True, .RedirectStandardOutput = True, .UseShellExecute = False, .WindowStyle = ProcessWindowStyle.Hidden}

    Using p As Process = New Process() With {.EnableRaisingEvents = True, .StartInfo = startInfo}

        AddHandler p.ErrorDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                            If Not String.IsNullOrEmpty(e.Data) Then
                                                'ToDo: add desired code
                                                Debug.WriteLine("error: " & e.Data)
                                            End If
                                        End Sub

        AddHandler p.OutputDataReceived, Sub(sender As Object, e As DataReceivedEventArgs)
                                             If Not String.IsNullOrEmpty(e.Data) Then
                                                 'ToDo: add desired code
                                                 Debug.WriteLine("output: " & e.Data)
                                             End If
                                         End Sub


        p.Start()

        p.BeginErrorReadLine()
        p.BeginOutputReadLine()

        Using sw As System.IO.StreamWriter = p.StandardInput
            'provide values for each input prompt
            'ToDo: add values for each input prompt - changing the for loop as necessary
            'Note: Since we only have 1 prompt, using a loop Is unnecessary - a single 'WriteLine' statement would suffice

            'if there are additional prompts add them below; else if (i = 1)...
            For i As Integer = 0 To 1
                If i = 0 Then
                    'write port name to StandardInput
                    sw.WriteLine(portName)
                End If
            Next
        End Using

        'wait for exit
        p.WaitForExit()
    End Using
End Sub

Usage:

RunProcessWithStandardInput("C:\Temp\TestEnvVar.bat", "COM5")

where "COM5" is your port number (replace this with the value from your ComboBox).

Additional Resources:

• Environment.GetEnvironmentVariable
• Environment.SetEnvironmentVariable
• RegistryKey Class

Answer 2

Well after much hard work and back and forth I finally figured out how to achieve my goal, I would like to thank @User09938 for sticking with me and for offering all the advice, is was just down to me to interpret it as a VB newbie and make it work for me.
I followed this guide see what is attached to a com port and show in combo box

and added the statement

Environment.SetEnvironmentVariable("port", ComboBoxComPorts.SelectedValue.ToString(), EnvironmentVariableTarget.Process) 

and

Environment.SetEnvironmentVariable("port", ComboBoxComPorts.SelectedValue.ToString(), EnvironmentVariableTarget.User)

Which worked.

To those who are adventuring into VB for the first time I have to say that this site is so very helpful