How to skip first line while reading csv using streamreader

Question

I have my following code to read values from CSV file and do some processing. I would like to skip the first row of the input CSV file as it contains header text but I'd want to add it back after the processing is done.

List<string> values = new List<string>();
using (StreamReader sr = new StreamReader(filePath))
{
    while (sr.Peek() != -1)
    {
        string line = sr.ReadLine();
        List<string> lineValues = line.Split(',').ToList();
        var tempMinInt = 1;
        var tempValue = 1;
        var tempValInt = Convert.ToInt32(lineValues[4]);
        if (lineValues[3] == "1876")
        {
            if (tempValInt % 60 != 0)
            {
                tempMinInt = (tempValInt / 60) + 1;
                tempValue = tempMinInt * 30;
            }
            else
            {
                tempMinInt = tempValInt / 60;
                tempValue = tempMinInt * 30;
            }
        }
        else if (lineValues[3] == "1875")
        {
            if (tempValInt != 0)
            {
                tempValue = 500;
            }
            else
                tempValue = 0;
        }

        if (lineValues[3] == "1876")
        {
            values.Add(string.Join(",", lineValues) + "," + "0" + "," + "30" + "," + tempValue.ToString());
        }
        else if (lineValues[3] == "1875")
        {
            values.Add(string.Join(",", lineValues) + "," + "1" + "," + "500" + "," + tempValue.ToString());
        }

    }
}

Sample input csv looks like this:

id, datetime, msisdn, num, duration
33083,2011-12-19 05:17:57+06:30,98590149,1875,258
33084,2011-12-19 05:22:28+06:30,98590149,1875,69
33085,2011-12-19 05:23:45+06:30,98590149,1875,151
33086,2011-12-19 05:30:21+06:30,98590149,1875,58
33087,2011-12-19 06:44:19+06:30,949826259,1875,66

And I'd like to have my output like this:

id, datetime, msisdn, num, duration, type, ammount, total
33083,2011-12-19 05:17:57+06:30,98590149,1875,258,1,500,500
33084,2011-12-19 05:22:28+06:30,98590149,1875,69,1,500,500
33085,2011-12-19 05:23:45+06:30,98590149,1875,151,1,500,500
33086,2011-12-19 05:30:21+06:30,98590149,1875,58,1,500,500

score 78 · Answer 1 · answered Feb 01 '12 at 09:11

78

Just read it first before you get into the loop. I'd do this:

using (StreamReader sr = new StreamReader(filePath))
{
    string headerLine = sr.ReadLine();
    string line;
    while ((line = sr.ReadLine()) != null)
    {
         ...
    }
}

(I don't like using Peek, personally.)

Then when you write out the output, start with headerLine.

answered Feb 01 '12 at 09:11

Jon Skeet

1,421,763
867
9,128
9,194

I rarely, if ever use Peek, but just curious...why don't you like using Peek? – Justin Mar 14 '22 at 01:49
1

@Justin: I tend to worry that there's a possibility of the data changing when you next read it - it feels cleaner to "read once and act" than to "read, check, then read again" and assume that the two reads will have the same results. It's entirely possible that the buffering details of whatever abstraction is in use (`StreamReader` in this case) can guarantee the result of `Peek` is consistent with the next read, but it feels cleaner not to have to worry about that. – Jon Skeet Mar 14 '22 at 06:52

score 20 · Answer 2 · answered Feb 01 '12 at 09:11

Just read the first line and do nothing with it...

List<string> values = new List<string>();
using (StreamReader sr = new StreamReader(filePath))
{
    sr.ReadLine();
    while (sr.Peek() != -1)
    {
        string line = sr.ReadLine();
        List<string> lineValues = line.Split(',').ToList();

        //***//
    }
}

score 6 · Answer 3 · answered Feb 01 '12 at 09:17

6

Something like this:

bool isFirst=true;
using (StreamReader sr = new StreamReader(filePath))
{
    while (sr.Peek() != -1)
    {
        if(isFirst)
        {
            isFirst=false;
            continue;
        }
    }
}

answered Feb 01 '12 at 09:17

Arion

31,011
10
70
88

score 2 · Answer 4 · answered Apr 17 '20 at 06:51

I recommend, to use technique to handle such situation,

                int row = 0;
                using (StreamReader sr = new StreamReader(filePath))

                {
                   While(reader.Read()) //Each row of the file
                    {
                        row++;
                        if(row==1)
                        {
                            continue;
                        }
               }
... code..
}

score 1 · Answer 5 · answered Feb 01 '12 at 09:11

1

You could read the first line before your while loop and store it, or you could use a counter / boolean field to check where in the file you are.

answered Feb 01 '12 at 09:11

cjk

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How to skip first line while reading csv using streamreader

5 Answers5

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