.net下几种实现MD5算法的途径

		/// <summary>
		/// 获取MD5得值，转换成BASE64
		/// </summary>
		/// <param name="Sourcein"></param>
		/// <returns></returns>
		public static string MD5(string Sourcein)
		{
			System.Security.Cryptography.MD5CryptoServiceProvider MD5CSP = new System.Security.Cryptography.MD5CryptoServiceProvider();
			byte[] MD5Source = System.Text.Encoding.UTF8.GetBytes(Sourcein);
			byte[] MD5Out = MD5CSP.ComputeHash(MD5Source);
			
			return Convert.ToBase64String(MD5Out);
		}


		/// <summary>
		/// 获取MD5得值，没有转换成Base64的
		/// </summary>
		/// <param name="sDataIn">需要加密的字符串</param>
		/// <param name="move">偏移量</param>
		/// <returns>sDataIn加密后的字符串</returns>
		public string GetMD5(string sDataIn, string move) 
		{
			System.Security.Cryptography.MD5CryptoServiceProvider md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
			byte[]byt, bytHash;
			byt = System.Text.Encoding.UTF8.GetBytes(move + sDataIn);
			bytHash = md5.ComputeHash(byt);
			md5.Clear();
			string sTemp = "";
			for (int i = 0; i < bytHash.Length; i ++ ) 
			{
				sTemp += bytHash[i].ToString("x").PadLeft(2, '0');
			}
			return sTemp;
		}

		/// <summary>
		/// ASP.net下获取Md5
		/// </summary>
		/// <param name="source"></param>
		/// <returns></returns>
		public string MD5AspDotNet(string source)
		{
			return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(source, "MD5");
		}

以上第一种方法获得的结果和后面几种方法的结果不一样，但是效果是一样的，如果你的程序是从ASP转过来的话，推荐使用第2种或第3种方法

扩展方法：

    static class StringExtensions
    {
        public static string Nl2Br(this string s)
        {
            return s.Replace("\r\n", "<br />").Replace("\n", "<br />");
        }

        public static string MD5(this string s)
        {
            MD5CryptoServiceProvider provider;
            provider = new MD5CryptoServiceProvider();
            byte[] bytes = Encoding.UTF8.GetBytes(s);
            StringBuilder builder = new StringBuilder();

            bytes = provider.ComputeHash(bytes);
           
            foreach (byte b in bytes)
                builder.Append(b.ToString("x2").ToLower());
           
            return builder.ToString();
        }
    }