Print-to-screen log window - vb.net

Question

I have to run a process - through the execution of a batch script - which produces an output that is saved as a text file. Furthermore, I need to see this output on a form of the application of mine and, to do this, I've set an iterative timer which updates every second the content of a non-editable RichTextBox but I have two issues:
Each time the timer stops and restarts, I need to create a copy the output file, since the file is used from another process and can't be loaded onto the software as it is;
Creating and loading this text file may be honerous in terms of hardware capability, since this file may reach really big size (even more than 5 GB).
Here is the code I'm providing:
Private Sub Form9_Load(sender As Object, e As EventArgs) Handles MyBase.Load
[...]
Me.Timer1.Interval = TimeSpan.FromSeconds(1).TotalMilliseconds
Me.Timer1.Start()
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
Application.DoEvents()
Dim p = Process.GetProcessesByName("fds2ftmi_win_64")
Dim appPath As String = Path.GetDirectoryName(Application.ExecutablePath)
If My.Computer.FileSystem.FileExists(Form1.TextBox5.Text + "/HTAoutput.dat") Then
If p.Count > 0 Then
RichTextBox1.Refresh()
My.Computer.FileSystem.CopyFile(Form1.TextBox5.Text + "/HTAoutput.dat", Form1.TextBox5.Text + "/HTAoutemp.dat", Microsoft.VisualBasic.FileIO.UIOption.OnlyErrorDialogs, FileIO.UICancelOption.DoNothing)
RichTextBox1.LoadFile(Form1.TextBox5.Text + "/HTAoutemp.dat", RichTextBoxStreamType.PlainText)
RichTextBox1.SelectionStart = RichTextBox1.TextLength
RichTextBox1.ScrollToCaret()
Else
Call Button3_Click(sender, e)
End If
End If
End Sub
Is there a more efficient way to show this stream-writing onto my log-window?
Thanks all are gonna answer me
EDIT 1:
Here is the code I'm providing:
Dim p = Process.GetProcessesByName("fds2ftmi_win_64")
Dim appPath As String = Path.GetDirectoryName(Application.ExecutablePath)
Dim str As FileStream
str = File.Open(Form1.TextBox5.Text + "/HTAoutput.dat", FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
If My.Computer.FileSystem.FileExists(Form1.TextBox5.Text + "/HTAoutput.dat") Then
If p.Count > 0 Then
RichTextBox1.LoadFile(str, RichTextBoxStreamType.PlainText)
RichTextBox1.SelectionStart = RichTextBox1.TextLength
RichTextBox1.ScrollToCaret()
Application.DoEvents()
Else
Call Button3_Click(sender, e)
End If
End If

Answer 1

Here is a simple demonstration of opening a file once and continuing to read only new data as it is added to that file.
Create a new WinForms Application project with two forms. Add a TextBox and a Button to each form. Make the TextBox multiline on Form1. Add a text file to your project named Test.txt and set Copy to Output Directory to Copy always. Add some default text to the file. Add this code to Form1:
Imports System.IO
Public Class Form1
Private reader As StreamReader
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Open the file for reading and allow sharing.
Dim filePath = Path.Combine(Application.StartupPath, "Test.txt")
Dim strm = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
reader = New StreamReader(strm)
'Read all available text and append to the existing text.
TextBox1.Text = reader.ReadToEnd()
Form2.Show()
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Read all available text and append to the existing text.
TextBox1.AppendText(reader.ReadToEnd())
End Sub
End Class
and add this code to Form2:
Imports System.IO
Public Class Form2
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim filePath = Path.Combine(Application.StartupPath, "Test.txt")
'Write a new line of text to the file.
File.AppendAllText(filePath, Environment.NewLine & TextBox1.Text)
'Get ready for the next line of text.
TextBox1.Clear()
TextBox1.Select()
End Sub
End Class
Run the project and you'll see your default text in Form1. Enter some text into Form2 and click the Button. Do that a few times. Now click the Button on Form1. Voila! Repeat that cycle and see the text you enter on one form magically appear on the other.
Now go back and examine the code more closely. You can see that Form2 appends a line of code to the file each time you click the Button. Form1 reads the initial contents of the file when it loads and displays that, but it keeps the file open. Each time you click the Button, it will read only the new data, i.e. only the data after where it previously read up to. It then appends that new text to the existing text in the TextBox.