MD5算法的使用

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


StringBuilder sb = new StringBuilder();//构建一个字符串,来接受进行算法后的字符串
            using (MD5 md=MD5.Create())//通过静态方法Creat()创建一个MD5对象
            {
　　　　　　　　　　//ComputeHash()方法接受的参数为byte[]数组或者流,所以要通过编码将"aa"编码为byte数组,然后再传参
                byte[] byteArr = md.ComputeHash(Encoding.UTF8.GetBytes("aa"));
                
                for (int i = 0; i < byteArr.Length; i++)
                {
                    sb.Append(byteArr[i].ToString("x2"));
                }
            }
            Console.WriteLine(sb.ToString());

 =====================================

对文件的MD5计算:

class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Please input the file's path...");
            string path = Console.ReadLine();

            FileStream aFiles = new FileStream(path, FileMode.Open, FileAccess.Read) ;
            Program a = new Program();
            a.comput(aFiles);
            Console.ReadLine();
        }
       public void comput(FileStream mdByteArr)
        {
                StringBuilder sb = new StringBuilder();
                using (MD5 md = MD5.Create())
                {
                    byte[] aFile = md.ComputeHash(mdByteArr);//直接传入一个流的重载
                    for (int i = 0; i < aFile.Length; i++)
                    {
                        sb.Append(aFile[i].ToString("x2"));
                    }
                }
                Console.WriteLine(" md5 value is: {0}", sb.ToString());
        }

    }

 用MD5来存储用户密码,实现登陆功能:

　　

 private void btnLogin_Click(object sender, EventArgs e)
        {
            string name = txtName.Text.Trim();
            string pwd = txtPwd.Text.Trim();
            string sqlstr = "select count(*)  from T_Seats where CC_LoginId=@id and CC_LoginPassword=@pwd";
            SqlParameter[] spt = new SqlParameter[] { 
                new SqlParameter("@id",name),
                new SqlParameter("@pwd",GetMd5Value(pwd))//拿到用户输入的密码的MD5值去跟数据库中的进行比较
            };
            if ((int)SqlHelper.ExecuteScalar(sqlstr, spt) > 0)
            {
                MessageBox.Show("access");
                txtRePwd.Visible = true;
                btnChangePwd.Visible = true;
            }
            else
            {
                MessageBox.Show("no");
            }
        }



private string GetMd5Value(string original)
        {
            StringBuilder sb = new StringBuilder();
            byte[] bytes = Encoding.Default.GetBytes(original);
            MD5 mdf = MD5.Create();
            byte[] endBytes = mdf.ComputeHash(bytes);
            for (int i = 0; i < endBytes.Length; i++)
            {
                sb.Append(endBytes[i].ToString("x2"));
            }
            mdf.Clear();
            return sb.ToString();
        }