Revision #2

How To execute a dos script in Visual Basic without creating an external process.
​Not all dos commands can be executed with this, such as CLS, diskpart, echo, etc.... If you discover unsupported commands, please add them to this list:
Unsupported Dos Commands:

• ​CLS
• Echo
• DiskPart
• ?

Option Strict On

Public Class Form1

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

        Dim OFD As New OpenFileDialog With {.Filter = "DOS Batch Files|*.bat", .Multiselect = False}

        If OFD.ShowDialog = DialogResult.OK Then

            ExecuteBatchFile(OFD.FileName)

        End If

    End Sub

    Public Function ExecuteDosScript(ByVal BatchScriptLines As List(Of String)) As String

        Dim OutputString As String = String.Empty

        Using Process As New Process

            AddHandler Process.OutputDataReceived, Sub(sendingProcess As Object, outLine As DataReceivedEventArgs)

                                                       OutputString = OutputString & outLine.Data & vbCrLf

                                                   End Sub

            Process.StartInfo.FileName = "cmd"

            Process.StartInfo.UseShellExecute = False

            Process.StartInfo.CreateNoWindow = True

            Process.StartInfo.RedirectStandardInput = True

            Process.StartInfo.RedirectStandardOutput = True

            Process.StartInfo.RedirectStandardError = True

            Process.Start()

            Process.BeginOutputReadLine()

            Using InputStream As System.IO.StreamWriter = Process.StandardInput

                InputStream.AutoFlush = True

                For Each ScriptLine As String In BatchScriptLines

                    InputStream.Write(ScriptLine & vbCrLf)

                Next

            End Using

            Do

                Application.DoEvents()

            Loop Until Process.HasExited

        End Using

        Return OutputString

    End Function

    Sub ExecuteBatchFile(ByVal Filename As String)

        If Not IO.Path.GetExtension(Filename).ToLower = ".bat" Then Throw New Exception("Invalid batch file extension")

        Dim BatchScriptLines As List(Of String) = IO.File.ReadAllLines(Filename).ToList

        MsgBox(ExecuteDosScript(BatchScriptLines))

    End Sub

End Class