c# Add a Column to end of CSV file

Question

Trying to add a column to the end of a cvs file, which will just count up the number of lines (or can all be the same number it doesn\'t really mater) as the main aim is to

Answer 1

Without examining much more, I can tell you that you definitely have a challenge with the lambda you're using for the update:

    //add new column value for each row.
    lines.Skip(1).ToList().ForEach(line =>
    {
        //-1 for header
        lines[index] += "," + newColumnData[index - 1];
        index++;
    });

This would make more sense to me:

    //add new column value for each row.
    lines.Skip(1).ToList().ForEach(line =>
    {
        line += "," + newColumnData[++index - 2];
    });

The lines[index] part doesn't make sense in a ForEach since you're looping through each line separately.