System.IO.File.ReadAllLines() method with progress bar in vb.net - vb.net

Question

I am reading a large text file in vb.net using System.IO.File.ReadAllLines(TextFileURL). Since the process takes a few seconds to finish, would there be a possibility to use a progress bar?
.
RawFile = System.IO.File.ReadAllLines(TextFileURL)
lines = RawFile.ToList
If arg = "" Then MsgBox("IMPORTER IS DONE")
.
There is no loop or anything that could be used to update the value of the progress bar. Any thoughts or workaround would be appreciated.

Answer 1

The following reads a pretty big .TXT file line by line and reports progress:
Code:
Imports System.IO
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim dialog As New OpenFileDialog
dialog.Filter = "Text|*.txt"
Dim result = dialog.ShowDialog()
If result <> DialogResult.OK Then
Return
End If
Dim stream = File.OpenRead(dialog.FileName)
Dim reader As New StreamReader(stream)
Dim percentage As Integer
While True
Dim line As String = Await reader.ReadLineAsync()
If line Is Nothing Then
Exit While
End If
' TODO do something with your line
Dim percentD As Double = 1D / stream.Length * stream.Position * 100D
Dim percentI As Integer = Math.Floor(percentD)
If percentI > percentage Then
ProgressBar1.Value = percentI
percentage = percentI
End If
End While
Await stream.DisposeAsync()
End Sub
End Class
Result:
Notes:
this puts a burden on the stream as ultimately reading a line is small data
try using a buffered stream to reduce pressure
notice that I only report when integer percentage is greater than previous
you'd overwhelm UI when updating the progress bar otherwise
there is trivial async usage, you may want to improve that overall
the progress bar doesn't exactly reach 100%, I let you fix that, it's pretty EZ to do

Answer 2

You can use ReadLines instead of ReadAllLines
as docs said, when you are working with very large files, ReadLines can be more efficient:
Dim lstOflines as List(Of String)
For Each line As String In File.ReadLines(TextFileURL)
lstOflines.Add(line)
Next line
For get the total number of lines, you can make a guess based on file Size instead processing two times the file
Code for getting filesize: (use before start processing)
Dim myFile As New FileInfo(TextFileURL)
Dim sizeInBytes As Long = myFile.Length