How to replace a row in a file in vb.net

Question

2.50/5 (2 votes)

See more:

I have a csv file which have data like this:

Date,val1,val2,val3,val4,val5,val6,.......val47,val48
18/07/2011,0,0,0,10.98,0,0,0,10.98,10.98,0,0,0,0,0....,0,0

Now i need to compare the date value of existing row with new row's date value. If equal then need to replace the existing row with new row. If not append the existing row. I tried in following way. If dates are not equal, the new row is getting added but if dates are equal could not able to replace the existing row. Any suggestions please?????

Imports System.IO
     Public Class Form1
    Private _fileName As String = "C:\Desktop\demo.csv"
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim reader As New StreamReader(_fileName)
        Dim line As String = reader.ReadLine
        Dim _newLine As String = "18/07/2011,0,0,0,0,0,0,0,10.98,10.98,0,0,0,0,10.98,0,0,0,10.98"
        While line <> ""

            line = reader.ReadLine

            If line <> "" Then
                Dim values() As String = line.Split(",")

                If values(0) = "18/07/2011" Then

                    _fileName.Replace(line, _newLine)

                End If

            End If

        End While
        reader.Close()
    End Sub
End Class

Posted 18-Jul-11 0:39am

Member 8001800

Updated 18-Jul-11 0:40am

Tarun.K.S

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Shameel · Answer 1 · 2011-07-18T00:46:00

Solution 1

You seem to use string comparison for comparing dates. You should always use DateTime.Equals() to compare dates, string comparison is prone to errors.
And what is this code?

VB

_fileName.Replace(line, _newLine)

Why are you replacing it in the filename variable, you should be replacing it in the actual file content.

Posted 18-Jul-11 0:46am

Shameel

Comments

Member 8001800 18-Jul-11 6:51am

So what is the suitable method in this case to replace the file contents?

[no name] 18-Jul-11 7:37am

If the file is not very large, you can read the contents using StreamReader, make the replacements on the fly and then save the new contents using a StreamWriter.

Member 8001800 18-Jul-11 8:40am

modified the while loop as below:

While line <> ""

line = reader.ReadLine

If line <> "" Then
Dim values() As String = line.Split(",")

If values(0) = "18/07/2011" Then

Dim newRow as string=line.Replace(line, _newLine)
Dim writer as new StreamWriter(_fileName)
writer.writeline(newRow)
writer.close()

End If

End If

End While

but while executing the Dim writer statement,getting exception as the file is being used by another process

Sergey Alexandrovich Kryukov · Answer 2 · 2011-07-18T08:55:00

Solution 2

Best suggestion I can make: stop using CSV. How much longer? As if XML is not enough (and much much more robust). Better yet, use Data Contract to stop this manual coding of persistence at all. See http://msdn.microsoft.com/en-us/library/ms733127.aspx[^].

—SA

Posted 18-Jul-11 8:55am

Sergey Alexandrovich Kryukov