C#加密解密，包括DES、MD5、SHA256

//加密解密
    public class GF_Encrypt
    {
        /// <summary>
        /// DES加密
        /// </summary>
        /// <param name="pToEncrypt">加密字符串</param>
        /// <param name="sKey">密钥</param>
        /// <returns></returns>
        public static string string_Encrypt(string pToEncrypt, string sKey)
        {
            if (pToEncrypt == "") return "";
            if (sKey.Length < 8) sKey = sKey + "xuE29xWp";
            if (sKey.Length > 8) sKey = sKey.Substring(0, 8);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            //把字符串放到byte数组中  
            //原来使用的UTF8编码，我改成Unicode编码了，不行  
            byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);
            //建立加密对象的密钥和偏移量  
            //原文使用ASCIIEncoding.ASCII方法的GetBytes方法  
            //使得输入密码必须输入英文文本  
            des.Key = ASCIIEncoding.Default.GetBytes(sKey);
            des.IV = ASCIIEncoding.Default.GetBytes(sKey);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            //Write  the  byte  array  into  the  crypto  stream  
            //(It  will  end  up  in  the  memory  stream)  
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //Get  the  data  back  from  the  memory  stream,  and  into  a  string  

            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                //Format  as  hex  
                ret.AppendFormat("{0:X2}", b);
            }
            ret.ToString();
            return ret.ToString();
        }
 
        /// <summary>
        /// DES解密
        /// </summary>
        /// <param name="pToDecrypt">解密字符串</param>
        /// <param name="sKey">解密密钥</param>
        /// <param name="outstr">返回值</param>
        /// <returns></returns> 
        public static bool string_Decrypt(string pToDecrypt, string sKey, out string outstr)
        {
            if (pToDecrypt == "")
            {
                outstr = "";
                return true;
            };
            if (sKey.Length < 8) sKey = sKey + "xuE29xWp";
            if (sKey.Length > 8) sKey = sKey.Substring(0, 8);
            try
            {
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                //Put  the  input  string  into  the  byte  array