Parse CSV in C#

using System;
using System.Collections.Generic;

namespace System.Text
{
    internal static class CsvEncoder
    {
        public static string Encode(List<string> strings)
        {
            StringBuilder result = new StringBuilder();
            char[] specialChars = new char[] { '"', ',', '\r', '\n' };

            foreach (string data in strings)
            {
                if (result.Length > 0)
                {
                    result.Append(',');
                }
                if (data.IndexOfAny(specialChars) == -1)
                {
                    result.Append(data.Trim());
                }
                else
                {
                    result.Append('"' + data.Trim().Replace("\"", "\"\"") + '"');
                }
            }
            return result.ToString();
        }

        public static List<string> Decode(string csvString)
        {
            List<string> result = new List<string>();
            char[] specialChars = new char[] { '"', ',' };

            int pos = 0;
            while (pos < csvString.Length)
            {
                if (csvString[pos] == '"')
                {
                    StringBuilder sb = new StringBuilder();
                    pos++;
                    while (true)
                    {
                        if (pos >= csvString.Length - 1)
                        {
                            if (sb.Length > 0)
                            {
                                result.Add(sb.ToString().Trim());
                            }
                            pos = csvString.Length;
                            break;
                        }
                        if (csvString[pos] == '"')
                        {
                            if (csvString[pos + 1] == ',')
                            {
                                if (sb.Length > 0)
                                {
                                    result.Add(sb.ToString().Trim());
                                    pos += 2;
                                    break;
                                }
                            }
                            else
                            {
                                sb.Append('"');
                                if (csvString[pos + 1] == '"')
                                {
                                    // This is to be expected. If not, then the string is invalid CSV.
                                    pos++;
                                }
                                pos ++;
                            }
                        }
                        else
                        {
                            sb.Append(csvString[pos]);
                            pos++;
                        }
                    }
                }
                else
                {
                    int commaPos = csvString.IndexOf(',', pos);
                    if (commaPos == -1)
                    {
                        string s = csvString.Substring(pos).Trim();
                        if (s.Length > 0)
                        {
                            result.Add(s);
                        }
                        pos = csvString.Length;
                    }
                    else
                    {
                        string s = csvString.Substring(pos, commaPos - pos).Trim();
                        if (s.Length > 0)
                        {
                            result.Add(s);
                        }
                        pos = commaPos + 1;
                    }
                }
            }

            return result;
        }
    }
}