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

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.

CodePudding user response：

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

CodePudding user response：

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