Reading and writing CSV files is something that will come up soon or later in your life as developer.

This is a small solution I've cooked up in a coupe of hours for a job interview.

public interface ICsvReaderWriter
{
    List Read(string filePath, char delimiter);
    void Write(string filePath, List lines, char delimiter);
}

public class CsvReaderWriter : ICsvReaderWriter
{
    public List Read(string filePath, char delimiter)
    {
        var fileContent = new List();
        using (var reader = new StreamReader(filePath, Encoding.Unicode))
        {
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                if (!string.IsNullOrEmpty(line))
                {
                    fileContent.Add(line.Split(delimiter));
                }
            }
        }
        return fileContent;
    }

    public void Write(string filePath, List lines, char delimiter)
    {
        using (var writer = new StreamWriter(filePath, true, Encoding.Unicode))
        {
            foreach (var line in lines)
            {
                var data = line.Aggregate(string.Empty, 
                                         (current, column) => current +
                                          string.Format("{0}{1}", column,delimiter))
                    .TrimEnd(delimiter);
                writer.WriteLine(data);
            }
        }
    }
}

This is a quick and dirty solution, I am sure there is plenty of room for improvment...let me know how you would improve it!!