1.使用TripleDES加密和解密:强度比较高

using System;
using System.Security.Cryptography;
using System.Text;

namespace CSST.Common
{
    public class TripleDESHelper
    {

        //-----------------:a1c2e3g4i5k6m7o8q9s0u1w2-----------

        private TripleDESHelper()
        {

        }

        public static string Encrypt(string toEncrypt, string key, bool useHashing)
        {
            try
            {
                byte[] keyArray;
                byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

                if (useHashing)
                {
                    MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                    keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                }
                else
                    keyArray = UTF8Encoding.UTF8.GetBytes(key);

                TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();

                tdes.Key = keyArray;
                tdes.Mode = CipherMode.ECB;
                tdes.Padding = PaddingMode.PKCS7;

                ICryptoTransform cTransform = tdes.CreateEncryptor();
                byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

                return Convert.ToBase64String(resultArray, 0, resultArray.Length);
            }
            catch
            {

            }
            return string.Empty;
        }

        public static string Decrypt(string toDecrypt, string key, bool useHashing)
        {
            try
            {
                byte[] keyArray;
                byte[] toEncryptArray = Convert.FromBase64String(toDecrypt);

                if (useHashing)
                {
                    MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                    keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                }
                else
                    keyArray = UTF8Encoding.UTF8.GetBytes(key);

                TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
                tdes.Key = keyArray;
                tdes.Mode = CipherMode.ECB;
                tdes.Padding = PaddingMode.PKCS7;

                ICryptoTransform cTransform = tdes.CreateDecryptor();
                byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

                return UTF8Encoding.UTF8.GetString(resultArray);

            }
            catch
            {

            }
            return string.Empty;

        }


    }
}


 2.MD5加密
        public static string MD5(string str)
        {
            if (str.Length > 0)
            {
                byte[] bytes = Encoding.Default.GetBytes(str);
                bytes = new MD5CryptoServiceProvider().ComputeHash(bytes);
                string str2 = "";
                for (int i = 0; i < bytes.Length; i++)
                {
                    str2 = str2 + bytes[i].ToString("x").PadLeft(2, '0');
                }
                return str2;
            }
            else
            {
                return string.Empty;
            }
        }
3.发送邮件

using System;
using System.Collections;

using System.Net.Mail;

namespace CSST.Common
{
    public class MailUnit
    {
        public string smtp;
        public string from;
        public string pwd;
        public string to;
        public string subject;
        public string body;
        public ArrayList paths;
        public MailUnit(string Psmtp, string Pfrom, string Ppwd, string Pto, string Psubject, string Pbody, ArrayList Ppaths)
        {
            smtp = Psmtp;
            from = Pfrom;
            pwd = Ppwd;
            to = Pto;
            subject = Psubject;
            body = Pbody;
            paths = Ppaths;
        }
        /*发邮件*/
        public bool SendMail()
        {
            //创建smtpclient对象
            System.Net.Mail.SmtpClient client = new SmtpClient();
            client.Host = smtp;
            client.UseDefaultCredentials = false;
            client.Credentials = new System.Net.NetworkCredential(from, pwd);
            client.DeliveryMethod = SmtpDeliveryMethod.Network;

            //创建mailMessage对象
            System.Net.Mail.MailMessage message = new MailMessage(from, to);
            message.Subject = subject;
            //正文默认格式为html
            message.Body = body;
            message.IsBodyHtml = true;
            message.BodyEncoding = System.Text.Encoding.UTF8;

            //添加附件
            if (paths.Count != 0)
            {
                foreach (string path in paths)
                {
                    Attachment data = new Attachment(path, System.Net.Mime.MediaTypeNames.Application.Octet);
                    message.Attachments.Add(data);
                }
            }

            try
            {
                client.Send(message);
                //MessageBox.Show("Email successfully sent.");
                return true;
            }
            catch (Exception ex)
            {
                //MessageBox.Show("Send Email Failed." + ex.ToString());
                throw new Exception(ex.Message);
                return false;
            }
        }

        /*发邮件：线程中使用*/
        public void SendMail2()
        {
            //All.runing++;
            //创建smtpclient对象
            System.Net.Mail.SmtpClient client = new SmtpClient();
            client.Host = smtp;
            client.UseDefaultCredentials = false;
            client.Credentials = new System.Net.NetworkCredential(from, pwd);
            client.DeliveryMethod = SmtpDeliveryMethod.Network;

            //创建mailMessage对象
            System.Net.Mail.MailMessage message = new MailMessage(from, to);
            message.Subject = subject;
            //正文默认格式为html
            message.Body = body;
            message.IsBodyHtml = true;
            message.BodyEncoding = System.Text.Encoding.UTF8;

            //添加附件
            if (paths.Count != 0)
            {
                foreach (string path in paths)
                {
                    Attachment data = new Attachment(path, System.Net.Mime.MediaTypeNames.Application.Octet);
                    message.Attachments.Add(data);
                }
            }

            try
            {
                client.Send(message);
                //All.success++;
                //All.runing--;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
                //All.fail++;
                //All.runing--;
            }
        }
    }
}