FileIO.TextFieldParser

Question

Hello,

Dim Blah As New FileIO.TextFieldParser(src)
MyTextParser.TextFieldType / .SetDelimiters / .TrimWhiteSpace etc
While Not MyTextParser.EndOfData
   Blah.ReadFields()...
End While

Before entering the While loop, how can I get how many times this loop will run to set a progress bar's max value?

I can try something like:

File.ReadAllLines(src).Length

But blank lines will make it invalid, does TextFieldParser return the number of elements going to read prior to the read?

Any way?

Thanks.

Answer 1

Try this approach too:

Dim fs As FileStream = New FileStream("...path...", FileMode.Open, FileAccess.Read, FileShare.Read, 1024)

ProgressBar1.Maximum = 100

Dim MyTextParser = New TextFieldParser(fs)
' set delimiters, etc...

While Not MyTextParser.EndOfData

    ProgressBar1.Value = CInt(fs.Position * 100 / fs.Length)

    Dim row As String() = MyTextParser.ReadFields()

    ' process the row...

End While

It will not scan the file twice.

Answer 2

Hi,@StewartBW. Welcome to Microsoft Q&A. To determine how many times the loop will run when using TextFieldParser in Visual Basic .NET, you could count the non-blank lines in the file.

TextFieldParser does not provide a direct method to get the number of records beforehand, but You can read the file once to count the non-blank lines. This will give you the number of iterations the loop will execute, which you can use to set the progress bar's maximum value.

This function reads the file line by line. It returns the total count of non-blank lines.

Imports System.IO

Imports Microsoft.VisualBasic.FileIO

Class MainWindow

    Sub Main(src As String, progressBar1 As ProgressBar)

        Dim totalLines As Integer = CountNonBlankLines(src)

        progressBar1.Maximum = totalLines

        progressBar1.Value = 0

        Dim MyTextParser As New FileIO.TextFieldParser(src)

        MyTextParser.TextFieldType = FileIO.FieldType.Delimited

        MyTextParser.SetDelimiters(",")

        While Not MyTextParser.EndOfData

            Dim fields As String() = MyTextParser.ReadFields()

            progressBar1.Value += 1

        End While

        MyTextParser.Close()

    End Sub

    Function CountNonBlankLines(ByVal filePath As String) As Integer

        Dim lineCount As Integer = 0

        Using reader As New StreamReader(filePath)

            While Not reader.EndOfStream

                Dim line As String = reader.ReadLine()

                If Not String.IsNullOrWhiteSpace(line) Then

                    lineCount += 1

                End If

            End While

        End Using

        Return lineCount

    End Function

    Private Sub Button_Click(sender As Object, e As RoutedEventArgs)

        Dim filePath As String = "C:\...\WpfApp1\file.csv"

        Main(filePath, ProgressBar1)

        tb.Text = CountNonBlankLines(filePath)

    End Sub

End Class

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation enable e-mail notifications if you want to receive the related email notification for this thread.