Question

I have a CSV file with many rows in which I need to update/replace column four’s value using VB.NET. There are no headers on the columns so the loop can start on row one.

infile.csv
“value1″,”value2″,”value3″,”value4”

After much googling, there are lots of examples on how to read and write CSV files, but none quite what is needed. I know there are multiple ways to accomplish this task, but a requirement is that it’s done with VB.NET. Any help would be greatly appreciated.

---

Final code ported from Marco’s C# answer

    Private Sub CSVmod(ByVal strFileName As String, ByVal newFileName As String)

    Dim strLines As String() = File.ReadAllLines(strFileName)
    Dim strList As New List(Of String)
    Dim strReplace As String = "test"

    For Each line In strLines
        Dim strValues As String() = line.Split(",")
        If (strValues.Length = 14) Then
            strValues(3) = strReplace

            strList.Add(String.Join(",", strValues))
        End If

    Next

    File.WriteAllLines(newFileName, strList.ToArray())

Answer 1

I’m sorry, but I can write it only in C#.
I think you won’t find many problems to convert to VB.NET.
Here is my code:

private void SubstFile(string filename, string newFileName)
{
    // Reading all rows of the file
    string[] lines = File.ReadAllLines(filename);

    List<string> list = new List<string>();
    foreach (string line in lines)
    {
        // For every row I split it with commas
        string[] values = line.Split(',');
        // Check to have 4 values
        if (values.Length == 4)
        {
            // Substitute fourth value
            values[3] = "new value";
            // Add modified row to list
            list.Add(String.Join(",", values));
        }
    }
    // Save list to new file
    File.WriteAllLines(newFileName, list.ToArray());
}

---

VB.NET version:

Private Sub SubstFile(filename As String, newFileName As String)
    ' Reading all rows of the file
    Dim lines As String() = File.ReadAllLines(filename)

    Dim list As List(Of String) = New List(Of String)()
    For Each line As String In lines
        ' For every row I split it with commas
        Dim values As String() = line.Split(","c)
        ' Check to have 4 values
        If values.Length = 4 Then        
            ' Substitute fourth value
            values(3) = "new value"
            ' Add modified row to list
            list.Add(String.Join(",", values))
        End If
    Next
    ' Save list to new file
    File.WriteAllLines(newFileName, list.ToArray())
End Sub