Encryption decryption of user passwords in C#

public string base64Encode(string data)
    {
        try
        {
            byte[] encData_byte = new byte[data.Length];
            encData_byte = System.Text.Encoding.UTF8.GetBytes(data);
            string encodedData = Convert.ToBase64String(encData_byte);
            return encodedData;
        }
        catch (Exception e)
        {
            throw new Exception("Error in base64Encode" + e.Message);
        }
    }

    public string base64Decode2(string sData)
    {
        System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
        System.Text.Decoder utf8Decode = encoder.GetDecoder();
        byte[] todecode_byte = Convert.FromBase64String(sData);
        int charCount = utf8Decode.GetCharCount(todecode_byte, 0, todecode_byte.Length);
        char[] decoded_char = new char[charCount];
        utf8Decode.GetChars(todecode_byte, 0, todecode_byte.Length, decoded_char, 0);
        string result = new String(decoded_char);
        return result;
    }