DataReader to CSV

public static List<string> ToCSV(this IDataReader dataReader, bool includeHeaderAsFirstRow, string separator)
{
    List<string> csvRows = new List<string>();
    StringBuilder sb = null;

    if (includeHeaderAsFirstRow)
    {
        sb = new StringBuilder();
        for (int index = 0; index < dataReader.FieldCount; index++)
        {
            if (dataReader.GetName(index) != null)
                sb.Append(dataReader.GetName(index));

            if (index < dataReader.FieldCount - 1)
                sb.Append(separator);
        }
        csvRows.Add(sb.ToString());
    }

    while (dataReader.Read())
    {
        sb = new StringBuilder();
        for (int index = 0; index < dataReader.FieldCount - 1; index++)
        {
            if (!dataReader.IsDBNull(index))
            {
                string value = dataReader.GetValue(index).ToString();
                if (dataReader.GetFieldType(index) == typeof(String))
                {
                    //If double quotes are used in value, ensure each are replaced but 2.
                    if (value.IndexOf("\"") >= 0)
                        value = value.Replace("\"", "\"\"");

                    //If separtor are is in value, ensure it is put in double quotes.
                    if (value.IndexOf(separator) >= 0)
                        value = "\"" + value + "\"";
                }
                sb.Append(value);
            }

            if (index < dataReader.FieldCount - 1)
                sb.Append(separator);
        }

        if (!dataReader.IsDBNull(dataReader.FieldCount - 1))
            sb.Append(dataReader.GetValue(dataReader.FieldCount - 1).ToString().Replace(separator, " "));

        csvRows.Add(sb.ToString());
    }
    dataReader.Close();
    sb = null;
    return csvRows;
}

List<string> rows = null;
using (SqlDataReader dataReader = command.ExecuteReader())
{
    rows = dataReader.ToCSV(includeHeadersAsFirstRow, separator);
    dataReader.Close();
}