// CODE1  建立MD5加密主函数
using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Web;
 using System.Security.Cryptography;
 using System.Text;

 namespace Ts.BusinessRules
 {
     /// <summary>
     /// 公共方法类
     /// </summary>
     public class Utitly
     {
         /// <summary>
         /// 使用MD5加密字符串
         /// </summary>
         /// <param name="str">待加密的字符</param>
         /// <returns></returns>
         public static string GetStrUseMD5(string str)
         {
             if(str.IsNullOrEmpty())
             {
                 return string.Empty;
             }
             MD5CryptoServiceProvider md5=new MD5CryptoServiceProvider();
             byte[] arr = UTF8Encoding.Default.GetBytes(str);
             byte[] bytes = md5.ComputeHash(arr);
             str = BitConverter.ToString(bytes);
             str=str.Replace("-", "");
             return str;
         }
     }
 } 
// CODE2 建立 string 类型的扩展方法
using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Web;

 namespace Ts.BusinessRules
 {
     /// <summary>
     /// 扩展方法
     /// </summary>
     public static class ExtendMethod
     {
         /// <summary>
         /// 判断字符串是否为空或Null
         /// </summary>
         /// <param name="str">字符串</param>
         /// <returns></returns>
         /// <remarks>创建人员(日期):★ben★(101029 13:41)</remarks>
         public static bool IsNullOrEmpty(this string str)
         {
             return string.IsNullOrEmpty(str);
         }
         /// <summary>
         /// 得到MD5加密后的字符
         /// </summary>
         /// <param name="str">待转换字符</param>
         /// <returns></returns>
         public static string ToMD5(this string str)
         {
             return Utitly.GetStrUseMD5(str);
         }
     }
 } 
 
// CODE3  字符串加密的使用方法
namespace Ts.BusinessRules
 {
     /// <summary>
     /// 公共方法类
     /// </summary>
     public class Utitly
     {        public string Test(string str)
         {
              string md5=str.ToMD5();             return md5;
         }    }
}