源码
 internal string Creat_Code(string s)
    {
        s = s.Replace("http", "");
        s = s.Replace("/", "");
        s = s.Replace(":", "");
        s = s.Replace(".", "");
        s = s + "goodkdhfd%$$h";
        string str = this.MD5_Method(s);
        string str2 = str.Substring(1, 5);
        string str3 = str.Substring(6, 5);
        string str4 = str.Substring(11, 5);
        string str5 = str.Substring(0x10, 5);  /*我就想知道这句市什么意思，其它的已经明白了*/
        return (str2 + "-" + str3 + "-" + str4 + "-" + str5);
    }

明白了~~~谢谢~~~很详细

不过还是有问题~~我按照这个算法计算出来的注册码不能注册
下面的市源代码

using System;
using System.Configuration;
using System.Web;
using System.Web.Security;

public class Program
{
    private string code;
    private string key;
    private string regcode;
    private string webUrl;

    public Program()
    {
    }

    public Program(string url)
    {
        this.webUrl = url;
    }

    public Program(string regcode, string code)
    {
        this.code = code;
        this.regcode = regcode;
    }

    internal string Creat_Code(string s)
    {
        s = s.Replace("http", "");
        s = s.Replace("/", "");
        s = s.Replace(":", "");
        s = s.Replace(".", "");
        s = s + "goodkdhfd%$$h";
        string str = this.MD5_Method(s);
        string str2 = str.Substring(1, 5);
        string str3 = str.Substring(6, 5);
        string str4 = str.Substring(11, 5);
        string str5 = str.Substring(0x10, 5);
        return (str2 + "-" + str3 + "-" + str4 + "-" + str5);
    }

    public bool Is_reg()
    {
        string host = HttpContext.Current.Request.Url.Host;
        if (host.ToUpper().Contains("LOCALHOST") || host.Contains("127.0.0.1"))
        {
            return true;
        }
        string s = ConfigurationManager.get_AppSettings()["weburl"].ToString();
        return (ConfigurationManager.get_AppSettings()["key"].ToString() == this.strkey(this.Creat_Code(s)));
    }

    internal string MD5_Method(string strSource)
    {
        return FormsAuthentication.HashPasswordForStoringInConfigFile(strSource, "MD5");
    }

    public bool reg(Program p)
    {
        string str = this.Creat_Code(p.regcode);
        if (p.code == str)
        {
            DB.SetValue("key", this.strkey(str));
            return true;
        }
        return false;
    }

    internal string strkey(string str)
    {
        return this.MD5_Method(str.Substring(5)).Substring(10, 20);
    }

    public string Code
    {
        get
        {
            return this.code;
        }
        set
        {
            this.code = value;
        }
    }

    public string Regcode
    {
        get
        {
            return this.regcode;
        }
        set
        {
            this.regcode = value;
        }
    }

    public string Weburl
    {
        get
        {
            return this.webUrl;
        }
        set
        {
            this.webUrl = value;
        }
    }
}


按照这个算法的话我用192.168.0.168做域名，最终S=1921680168goodkdhfd%$$h   
经过MD5加密以后就市fb68d 96173 a0c96 43754 d830f 527cc d7（空格我自己加的）
那它的注册码应该是b68d9-6173a-0c964-3754d
可是注册确是失败的，能告诉我市为什么吗？

我得出的结果正确了·~是我的大小写忘记了~~要大写，嘿嘿，谢谢你哈！