C# Parsing a text file misses the first line of every text file

Question

I am making a number to music note value converter from text files and I am having trouble parsing text files in my C# code. The stream reader or parser seems to ignore every first line of text from different text files, I am learning from parsing CSV and assumed that I can parse text files the same way that I can parse CSV files. Here is my code:

static List<NoteColumns> ReadNoteValues(string fileName)
    {
        var allNotes = new List<NoteColumns>();
        using (var reader = new StreamReader(fileName))
        {
            string line = "";
            reader.ReadLine();
            while ((line = reader.ReadLine()) != null)
            {
                string[] cols = line.Split('|');
                var noteColumn = new NoteColumns();
                if (line.StartsWith("-"))
                {
                    continue;
                }
                double col;
                if (double.TryParse(cols[0], out col))
                {
                    noteColumn.QCol = col;
                }
                if (double.TryParse(cols[1], out col))
                {
                    noteColumn.WCol = col;
                }
            }
        }
        return allNotes;
    }

Here are the first 4 lines of one of my text file:

0.1|0.0|
0.0|0.1|
0.3|0.0|
0.1|0.0|

So every time that I have an output it will always skip the first line and move onto the next line. After it misses the first line it converts all the other values perfectly.

I have tried using a foreach loop but I end up getting an 'Index Out Of Range Exception'. Am I missing something/being stupid? Thanks for your time

If you copied that code for some CSV parsing algorithm it's likely that the `reader.ReadLine` before the `while` loop as intentionally skipping the first line because it expected that to be a line of headers for the columns. — juharr, Jul 20 '18 at 14:19

score 4 · Accepted Answer · answered Jul 20 '18 at 14:15

4

You have a call to reader.ReadLine(); before your loop, which you don't assign to anything

answered Jul 20 '18 at 14:15

johnny 5

19,893
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Oh dear, how silly of me. Thank goodness for your good eyes! Thank you so much for your help! – 50Wizards Jul 20 '18 at 14:19
Np, this happens to me all the time, sometimes you just need a second pair of eyes to find the issue, – johnny 5 Jul 20 '18 at 14:20

score 4 · Answer 2 · answered Jul 20 '18 at 14:16

4

It's because you have already added ReadLine() before the while loop which skips the first line

answered Jul 20 '18 at 14:16

Ipsit Gaur

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score 1 · Answer 3 · answered Jul 20 '18 at 14:22

In order to avoid such errors (erroneous reader.ReadLine() in the beginning) get rid of Readers at all and query file with Linq (let .Net open and close the file, read it line after line and do all low level work for you):

using System.IO;
using System.Linq;

...  

static List<NoteColumns> ReadNoteValues(string fileName) {
  return File
    .ReadLines(fileName)
    .Where(line => !line.StartsWith('-'))
    .Select(line => line.Split('|'))
    .Select(cols => {
        var noteColumn = new NoteColumns();

        if (double.TryParse(cols[0], out var col))
          noteColumn.QCol = col;

        if (double.TryParse(cols[1], out var col))
          noteColumn.WCol = col;

        return noteColumn;  
     })
    .ToList();
}

Wow, this fixes the OP's issue and cleans up the code +1 – johnny 5 Jul 20 '18 at 14:30 — johnny 5, Jul 20 '18 at 14:30

C# Parsing a text file misses the first line of every text file

3 Answers3