public static string Md5(string str)
        {
            System.Security.Cryptography.MD5CryptoServiceProvider hashmd5;
            hashmd5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
            return BitConverter.ToString(hashmd5.ComputeHash(System.Text.Encoding.Default.GetBytes(str))).Replace("-", "").ToLower();
        }

public string HashTextMD5(string plainString)
        {
            if(plainString.Equals(string.Empty))
            {
                return plainString;
            }            
            MD5CryptoServiceProvider md5=new MD5CryptoServiceProvider();
            byte[] btaValue=System.Text.Encoding.UTF8.GetBytes(plainString);
            byte[] btaHash=md5.ComputeHash(btaValue);            
            md5.Clear();
            string strtemp="";
            string strtemp2;
            for(int ii=0;ii<btaHash.Length;ii++)
            {
                strtemp2=btaHash[ii].ToString("x").ToUpper();
                if(strtemp2.Length<2)
                {
                    strtemp2="0"+strtemp2;
                }
                strtemp=strtemp+strtemp2;
            }
            return strtemp;
        }