How to read the text file lines with passing over some lines?

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I have a text file that contains some info in lines. I wanna read it by passing over some lines. For example, let's say i have 1-10 in the lines. When i'm reading i want to read it in the following way

1 <- i wanna read this
2 <- Skip this
3 <- read this
4 <- Skip this
5 <- read this
6 <- Skip this
7 <- read this
8 <- Skip this
9 <- read this
10 <- Skip this

you get the pattern right? how can i achieve this using c#? and i wanna get the lines i skipped at a later time too. Any ideas?

Posted 22-Jun-12 12:28pm

phantomlakshan

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Pascal Ganaye · Accepted Answer · 2012-06-22T12:55:00

Because you can't really know how long is each line, there is no easy way to skip a line without reading it first.
Typically you'll have to read all the lines but discard the 2 even lines.

C#

string filePath = @"c:\windows\win.ini";

using (var fileReader = new System.IO.StreamReader(filePath))
{
    int lineNo = 1;
    string line;
    while (true)
    {
        line = fileReader.ReadLine();
        if (line == null) break; // we have reached the end of the file
        bool oddLine = ((lineNo % 2) == 1);
        if (oddLine) Console.WriteLine(lineNo + " " + line);
        lineNo++;
    }
}

This will output every other line:

1 ; for 16-bit app support
3 [extensions]
5 [files]
7 MAPI=1
9 CMC=1
11 MAPIXVER=1.0.0.1
13 [MCI Extensions.BAK]
15 3gp=MPEGVideo
17 3gpp=MPEGVideo
19 adt=MPEGVideo
21 m2t=MPEGVideo
23 m2v=MPEGVideo

Clifford Nelson · Accepted Answer · 2012-06-22T14:21:00

Solution 2

You have the problem as stated above. However, I can give you an even easier way to readlines:

string[] lines = File.ReadLines(filePath);

See http://msdn.microsoft.com/en-us/library/dd383503.aspx[^]

Posted 22-Jun-12 14:21pm

Clifford Nelson

Comments

Tim Corey 22-Jun-12 21:38pm

Nice addition. +5

Prosan · Accepted Answer · 2012-06-22T19:43:00

look this example:-

C#

private void ReadLinesNoFromFile(string FileNameWithPath)
        {
            string[] bt = null;
            if (System.IO.File.Exists(FileNameWithPath))
            {
                bt = System.IO.File.ReadAllLines(FileNameWithPath);
            }
string str =""
            for (int i = 0; i < bt.Length; i++)
            {
                if ((i+1 % 2)==1)
           str = str +i.ToString() + "<- read this" + bt[i].ToString();// read file line
        else
          str = str + i.ToString() + "<- Skip this" // no read file line

            }
        }

kishhr · Accepted Answer · 2012-06-23T00:28:00

Solution 4

A variation and most effecient method to do the same:

C#

string filePath = @"c:\windows\win.ini";

using (var fileReader = new System.IO.StreamReader(filePath))
{
    int lineNo = 1;
    string line;
    while (true)
    {
        if(line % 2 ==0)
           {
               line = fileReader.ReadLine();
         }
    }
}

Posted 23-Jun-12 0:28am

kishhr

Comments

Sandeep Mewara 23-Jun-12 9:36am

How is this an answer? your while loop will never end and it will go into infinite loop.

[no name] 23-Jun-12 14:26pm

There is something called commonsense my friend, what you need to see there is line%2 == 0

Sandeep Mewara 23-Jun-12 16:12pm

:) and you think that 'if' not executing will take execution out of while loop? Yeah... common-sense!

Richard MacCutchan 24-Jun-12 6:46am

Take a look at his rant in Bugs & Sugs; it tells you a lot.

Richard MacCutchan 24-Jun-12 6:48am

Even if this would compile it will not work.

How to read the text file lines with passing over some lines?

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