Loading large text (log file) into a text box without freezing up / hanging the form

Question

I want to create a log viewer in my app to view log files create by my app (plain .txt files), they can be quite large.

I want to show them on screen.

I assume best control will be a simple multi-line text box?

How to load them without freezing up the form whilst it is loading all the lines.

Currently using below but as I say it does lockup form for a short while if log file is large

TextBox1.Text = System.IO.File.ReadAllText(filename)

Any better solutions.

Second question - any text boxes or other controls where I can show line numbers?

Thanks

Answer 1

    Private Sub RichTextBox1_VScroll(sender As Object, e As EventArgs) Handles RichTextBox1.VScroll
        If Not BackgroundWorker1.IsBusy AndAlso pointer < lines.Count Then BackgroundWorker1.RunWorkerAsync()
    End Sub
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        If Not BackgroundWorker1.IsBusy AndAlso pointer < lines.Count Then BackgroundWorker1.RunWorkerAsync()
    End Sub

Answer 2

Found two other great solutions - which I wanted to share here for anyone else finding this question

Fast Coloured Text Box (FCTB) - has a control for WinForms - works really quickly and very customizable with great demos

https://github.com/PavelTorgashov/FastColoredTextBox

https://www.nuget.org/packages/FCTB/

ScintillaNET - which also has a control for WinForms - this loads large text files almost instantly and allows you to show numbering down left hand side

https://github.com/jacobslusser/ScintillaNET

https://github.com/robinrodricks/ScintillaNET.Demo

https://www.nuget.org/packages/Scintilla.NET/

Answer 3

Hi

The time is mostly used by the interaction with whatever 'container' you are putting the text. I can read in a 135MB text file in less than 1 second, but more than a minute to put it into a TextBox or RichTextBox.

The Form 'lockup' is easily overcome, using (say) a BackGroundWorker, which would load the text in the background keeping the UI responsive for the User.

What is the largest file size you would expect to use?

Try out this example to see if it helps - just change path to suit, and edit the block size (maybe a little experimentation with different sizes)

' Form1 with:  
' RichTextBox1,  Button1  
' and Label1  
  
Option Strict On  
Option Explicit On  
Public Class Form1  
	Dim lines() As String  
	Dim pointer As Integer = 0  
  
	' set blocksize to suit  
	Dim blocksize As Integer = 10  
	Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
		lines = IO.File.ReadAllLines("C:\Users\lesha\Desktop\freddy.txt")  
  
		' read in first chunk  
		BackgroundWorker1.RunWorkerAsync()  
  
	End Sub  
	Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork  
		Dim current As Integer = pointer + blocksize  
		Do  
			Invoke(Sub() RichTextBox1.AppendText(lines(pointer) & vbCrLf))  
			pointer += 1  
		Loop Until pointer = current Or pointer = lines.Count  
		Invoke(Sub() Label1.Text = pointer.ToString)  
	End Sub  
	Private Sub RichTextBox1_VScroll(sender As Object, e As EventArgs) Handles RichTextBox1.VScroll  
		If pointer < lines.Count Then BackgroundWorker1.RunWorkerAsync()  
	End Sub  
	Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click  
		If pointer < lines.Count Then BackgroundWorker1.RunWorkerAsync()  
	End Sub  
End Class  

Answer 4

Hi

OK, sorry that my code is not of use. Maybe someone else will offer a more reliable solution that doesn't require any work on your part.