How to eliminate some rows and columns from a CSV file and save to new CSV? - vb.net

Question

I have a csv file, where the first 3 rows have unwanted data. The 4th row has needed data in the first column only. There are 4 more rows with unwanted data. Rows 9 through the end have needed data. Starting with row 9 there are 11 columns of data, columns 1 through 6 are needed, columns 7 through 11 are unwanted.
I have code that uses a DataGridView for temporary storage. It provides the parsing described above, however I don't need to view the data, I need to create a new CSV file resulting from the parsing.
There is probably a method using a data table for temporary storage, instead of the DataGridView, however maybe there is a simpler way using LINQ. I have no experience with LINQ and my experience with data tables is very limited. I am very comfortable with DataGridView since I use it extensively, but as I wrote earlier I don't need to display the result.
I tried the code in: https://www.codeproject.com/questions/634373/how-to-delete-the-rows-in-csv-file. But it doesn't fit my situation. The code below works using a DataGridView for temporary storage but I am sure there is a better way.
Using MyReader As New TextFieldParser(racerFile)
Dim currentRow As String()
MyReader.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
MyReader.Delimiters = New String() {","}
currentRow = MyReader.ReadFields()
currentRow = MyReader.ReadFields()
currentRow = MyReader.ReadFields()
boatClass = MyReader.ReadFields()(0)
currentRow = MyReader.ReadFields()
currentRow = MyReader.ReadFields()
currentRow = MyReader.ReadFields()
currentRow = MyReader.ReadFields()
While Not MyReader.EndOfData
Try
Dgvs.Rows.Add()
currentRow = MyReader.ReadFields()
Dgvs(0, rd).Value = boatClass
Dgvs(1, rd).Value = currentRow(1)
Dgvs(2, rd).Value = currentRow(2)
Dgvs(3, rd).Value = currentRow(3)
Dgvs(4, rd).Value = currentRow(4)
Dgvs(5, rd).Value = currentRow(5)
rd += 1
Catch ex As Exception
End Try
End While
End Using
Using WriteFile As New StreamWriter(myFile)
For x As Integer = 0 To Dgvs.Rows.Count - 1
For y As Integer = 0 To Dgvs.Columns.Count - 1
WriteFile.Write(Dgvs.Rows(x).Cells(y).Value)
If y <> Dgvs.Columns.Count - 1 Then
WriteFile.Write(", ")
End If
Next
WriteFile.WriteLine()
Next
End Using
I need a CSV file for output.

Answer 1

Instead of storing values in a DatGridView, you could store them in a List(Of String), where each string in the list is a line of the output csv file.
Dim output As New List(Of String)
While Not MyReader.EndOfData
Try
currentRow = MyReader.ReadFields()
Dim line As String
line = boatClass
line = line & "," & currentRow(1).ToString
line = line & "," & currentRow(2).ToString
line = line & "," & currentRow(3).ToString
line = line & "," & currentRow(4).ToString
line = line & "," & currentRow(5).ToString
output.Add(line)
Catch ex As Exception
End Try
End While
And then you write output lines as follows.
Using WriteFile As New StreamWriter(myFile)
For Each line As String In output
WriteFile.Write(line)
Next
End Using