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', '', '', '', '', '', '', '', '', '', '', '+', '/', '=' };
             byte empty = (byte);
             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 / ;
             int use = ;
             if ((use = messageLen % ) > )
             {
                 for (int i = ; i <  - 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 * ); for (int i = ; i < page; i++)
             {
                 //取一组3个字节的组
                 byte[] instr = new byte[]; instr[] = (byte)byteMessage[i * ]; instr[] = (byte)byteMessage[i *  + ]; instr[] = (byte)byteMessage[i *  + ];
                 //六个位为一组，补0变成4个字节
                 int[] outstr = new int[];
                 //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[] = instr[] >> ;
                 //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[] = ((instr[] & 0x03) << ) ^ (instr[] >> );
                 //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[].Equals(empty)) outstr[] = ((instr[] & 0x0f) << ) ^ (instr[] >> ); else outstr[] = ;
                 //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[].Equals(empty)) outstr[] = (instr[] & 0x3f); else outstr[] = ; outmessage.Append(Base64Code[outstr[]]);
                 outmessage.Append(Base64Code[outstr[]]);
                 outmessage.Append(Base64Code[outstr[]]);
                 outmessage.Append(Base64Code[outstr[]]);
             }
             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 % ) != )
             {
                 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 / ;
             System.Collections.ArrayList outMessage = new System.Collections.ArrayList(page * );
             char[] message = Message.ToCharArray();
             for (int i = ; i < page; i++)
             {
                 byte[] instr = new byte[];
                 instr[] = (byte)Base64Code.IndexOf(message[i * ]);
                 instr[] = (byte)Base64Code.IndexOf(message[i *  + ]);
                 instr[] = (byte)Base64Code.IndexOf(message[i *  + ]);
                 instr[] = (byte)Base64Code.IndexOf(message[i *  + ]);
                 byte[] outstr = new byte[];
                 outstr[] = (byte)((instr[] << ) ^ ((instr[] & 0x30) >> ));
                 if (instr[] != )
                 {
                     outstr[] = (byte)((instr[] << ) ^ ((instr[] & 0x3c) >> ));
                 }
                 else
                 {
                     outstr[] = ;
                 }
                 if (instr[] != )
                 {
                     outstr[] = (byte)((instr[] << ) ^ instr[]);
                 }
                 else
                 {
                     outstr[] = ;
                 }
                 outMessage.Add(outstr[]);
                 if (outstr[] != ) outMessage.Add(outstr[]);
                 if (outstr[] != ) outMessage.Add(outstr[]);
             }
             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

     }