C#帮助类：Base64

    public class Base64
    {
        #region Base64加密
        ///<summary>
        ///Base64加密
        ///</summary>
        ///<paramname="Message"></param>
        ///<returns></returns>
        public static string Base64Code(string Message)
        {
            char[] Base64Code = new char[] { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/', '=' };
            byte empty = (byte)0;
            System.Collections.ArrayList byteMessage = new System.Collections.ArrayList(System.Text.Encoding.Default.GetBytes(Message));
            System.Text.StringBuilder outmessage;
            int messageLen = byteMessage.Count;
            //将字符分成3个字节一组，如果不足，则以0补齐
            int page = messageLen / 3;
            int use = 0;
            if ((use = messageLen % 3) > 0)
            {
                for (int i = 0; i < 3 - use; i++) byteMessage.Add(empty);
                page++;
            }
            //将3个字节的每组字符转换成4个字节一组的。3个一组，一组一组变成4个字节一组
            //方法是：转换成ASCII码，按顺序排列24位数据，再把这24位数据分成4组，即每组6位。再在每组的的最高位前补两个0凑足一个字节。
            outmessage = new System.Text.StringBuilder(page * 4); for (int i = 0; i < page; i++)
            {
                //取一组3个字节的组
                byte[] instr = new byte[3]; instr[0] = (byte)byteMessage[i * 3]; instr[1] = (byte)byteMessage[i * 3 + 1]; instr[2] = (byte)byteMessage[i * 3 + 2];
                //六个位为一组，补0变成4个字节
                int[] outstr = new int[4];
                //第一个输出字节：取第一输入字节的前6位，并且在高位补0，使其变成8位（一个字节）
                outstr[0] = instr[0] >> 2;
                //第二个输出字节：取第一输入字节的后2位和第二个输入字节的前4位（共6位），并且在高位补0，使其变成8位（一个字节）
                outstr[1] = ((instr[0] & 0x03) << 4) ^ (instr[1] >> 4);
                //第三个输出字节：取第二输入字节的后4位和第三个输入字节的前2位（共6位），并且在高位补0，使其变成8位（一个字节）
                if (!instr[1].Equals(empty)) outstr[2] = ((instr[1] & 0x0f) << 2) ^ (instr[2] >> 6); else outstr[2] = 64;
                //第四个输出字节：取第三输入字节的后6位，并且在高位补0，使其变成8位（一个字节）
                if (!instr[2].Equals(empty)) outstr[3] = (instr[2] & 0x3f); else outstr[3] = 64; outmessage.Append(Base64Code[outstr[0]]);
                outmessage.Append(Base64Code[outstr[1]]);
                outmessage.Append(Base64Code[outstr[2]]);
                outmessage.Append(Base64Code[outstr[3]]);
            }
            return outmessage.ToString();
        }
        #endregion Base64加密
        #region Base64解密
        ///<summary>///Base64解密
        ///</summary>
        ///<paramname="Message"></param>
        ///<returns></returns>
        public static string Base64Decode(string Message)
        {
            if ((Message.Length % 4) != 0)
            {
                throw new ArgumentException("不是正确的BASE64编码，请检查。", "Message");
            }
            if (!System.Text.RegularExpressions.Regex.IsMatch(Message, "^[A-Z0-9/+=]*$", System.Text.RegularExpressions.RegexOptions.IgnoreCase))
            {
                throw new ArgumentException("包含不正确的BASE64编码，请检查。", "Message");
            }
            string Base64Code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
            int page = Message.Length / 4;
            System.Collections.ArrayList outMessage = new System.Collections.ArrayList(page * 3);
            char[] message = Message.ToCharArray();
            for (int i = 0; i < page; i++)
            {
                byte[] instr = new byte[4];
                instr[0] = (byte)Base64Code.IndexOf(message[i * 4]);
                instr[1] = (byte)Base64Code.IndexOf(message[i * 4 + 1]);
                instr[2] = (byte)Base64Code.IndexOf(message[i * 4 + 2]);
                instr[3] = (byte)Base64Code.IndexOf(message[i * 4 + 3]);
                byte[] outstr = new byte[3];
                outstr[0] = (byte)((instr[0] << 2) ^ ((instr[1] & 0x30) >> 4));
                if (instr[2] != 64)
                {
                    outstr[1] = (byte)((instr[1] << 4) ^ ((instr[2] & 0x3c) >> 2));
                }
                else
                {
                    outstr[2] = 0;
                }
                if (instr[3] != 64)
                {
                    outstr[2] = (byte)((instr[2] << 6) ^ instr[3]);
                }
                else
                {
                    outstr[2] = 0;
                }
                outMessage.Add(outstr[0]);
                if (outstr[1] != 0) outMessage.Add(outstr[1]);
                if (outstr[2] != 0) outMessage.Add(outstr[2]);
            }
            byte[] outbyte = (byte[])outMessage.ToArray(Type.GetType("System.Byte"));
            return System.Text.Encoding.Default.GetString(outbyte);
        }
        #endregion Base64解密
        #region RSA加密解密
        /// <summary>
        /// RSA加密
        /// </summary>
        /// <param name="publickey"></param>
        /// <param name="content"></param>
        /// <returns></returns>
        public static string RSAEncrypt(string publickey, string content)
        {
            publickey = @"<RSAKeyValue><Modulus>5m9m14XH3oqLJ8bNGw9e4rGpXpcktv9MSkHSVFVMjHbfv+SJ5v0ubqQxa5YjLN4vc49z7SVju8s0X4gZ6AzZTn06jzWOgyPRV54Q4I0DCYadWW4Ze3e+BOtwgVU1Og3qHKn8vygoj40J6U85Z/PTJu3hN1m75Zr195ju7g9v4Hk=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            byte[] cipherbytes;
            rsa.FromXmlString(publickey);
            cipherbytes = rsa.Encrypt(Encoding.UTF8.GetBytes(content), false);

            return Convert.ToBase64String(cipherbytes);
        }

        /// <summary>
        /// RSA解密
        /// </summary>
        /// <param name="privatekey"></param>
        /// <param name="content"></param>
        /// <returns></returns>
        public static string RSADecrypt(string privatekey, string content)
        {
            privatekey = @"<RSAKeyValue><Modulus>5m9m14XH3oqLJ8bNGw9e4rGpXpcktv9MSkHSVFVMjHbfv+SJ5v0ubqQxa5YjLN4vc49z7SVju8s0X4gZ6AzZTn06jzWOgyPRV54Q4I0DCYadWW4Ze3e+BOtwgVU1Og3qHKn8vygoj40J6U85Z/PTJu3hN1m75Zr195ju7g9v4Hk=</Modulus><Exponent>AQAB</Exponent><P>/hf2dnK7rNfl3lbqghWcpFdu778hUpIEBixCDL5WiBtpkZdpSw90aERmHJYaW2RGvGRi6zSftLh00KHsPcNUMw==</P><Q>6Cn/jOLrPapDTEp1Fkq+uz++1Do0eeX7HYqi9rY29CqShzCeI7LEYOoSwYuAJ3xA/DuCdQENPSoJ9KFbO4Wsow==</Q><DP>ga1rHIJro8e/yhxjrKYo/nqc5ICQGhrpMNlPkD9n3CjZVPOISkWF7FzUHEzDANeJfkZhcZa21z24aG3rKo5Qnw==</DP><DQ>MNGsCB8rYlMsRZ2ek2pyQwO7h/sZT8y5ilO9wu08Dwnot/7UMiOEQfDWstY3w5XQQHnvC9WFyCfP4h4QBissyw==</DQ><InverseQ>EG02S7SADhH1EVT9DD0Z62Y0uY7gIYvxX/uq+IzKSCwB8M2G7Qv9xgZQaQlLpCaeKbux3Y59hHM+KpamGL19Kg==</InverseQ><D>vmaYHEbPAgOJvaEXQl+t8DQKFT1fudEysTy31LTyXjGu6XiltXXHUuZaa2IPyHgBz0Nd7znwsW/S44iql0Fen1kzKioEL3svANui63O3o5xdDeExVM6zOf1wUUh/oldovPweChyoAdMtUzgvCbJk1sYDJf++Nr0FeNW1RB1XG30=</D></RSAKeyValue>";
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            byte[] cipherbytes;
            rsa.FromXmlString(privatekey);
            cipherbytes = rsa.Decrypt(Convert.FromBase64String(content), false);

            return Encoding.UTF8.GetString(cipherbytes);
        }
        #endregion RSA加密解密

    }