Streamreader reading the same line multiple times C#

Question

My old method (other than being wrong in general) takes too long to get multiple lines from a file and then store the parameters into a dictionary. Essentially it's open file, grab every second line one at a time, modify the line then store the data (line pos and the first element of the line (minus) ">") close the file and then repeat.

for (int i = 0; i < linecount - 1; i += 2)
{
    string currentline = File.ReadLines 
    (datafile).Skip(i).Take(1).First();
    string[] splitline = currentline.Split(' ');
    string filenumber = splitline[0].Trim('>');
}   for (int i = 0; i < linecount - 1; i += 2)

Answer 1

The issue is that you only ever read the first line of the file. To solve this you need to ensure you call sr.ReadLine() on every iteration through the loop. This would look like:

using (StreamReader sr = File.OpenText(datafile))
{
    string line = sr.ReadLine();
    while (line != null)
    {
        count = count ++;
        if (count % 2 == 0)
        {
            string[] splitline = line.Split(' ');
            string datanumber = splitline[0].Trim('>');
            index.Add(datanumber, count);
        }

        line = sr.ReadLine();
    }
}

This means on each iteration, the value of line will be a new value (from the next line of the file).