C#怎么判断域名是否合法

[zn3051644]

C#怎么判断域名是否合法

[人傻且呆但不萌]

string input = Console.ReadLine();
bool b=Regex.IsMatch(input,"[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+.?")
if(b)
Console.WriteLine("合法");
else
Console.WriteLine("不合法");

[心灵彩虹]

C# 正则域名 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Text.RegularExpressions;

namespace rexurl
{
    class Program
    {
        static void Main(string[] args)
        {
            string regex = @"(?i)http://(\w+\.){2,3}(com(\.cn)?|cn|net)\b";
            string content = "http://www.17meiman.com/u/20090313/15/5ad5d3f2-094f-4b01-9c91-a6d4052a8255.html";
            Regex re1 = new Regex(regex);
            MatchCollection matches = re1.Matches(content);
            System.Collections.IEnumerator enu = matches.GetEnumerator();

            while (enu.MoveNext() && enu.Current != null)
            {

                Match match = (Match)(enu.Current);
                string str = match.Value;
                Console.Write(str);

            }
            Console.Read();
        }
    }
}

[心灵彩虹]

1\关于域名解析  作用：可以把域名转换成IP地址

[csharp] view plaincopyprint?
using System.Net;  
  
        public static string domain2ip(string str)  
        {  
            string _return = "";  
            try  
            {  
               IPHostEntry hostinfo = Dns.GetHostByName(str);  
               IPAddress[] aryIP = hostinfo.AddressList;  
                _return = aryIP[0].ToString();  
  
            }  
            catch (Exception e)  
            {  
                _return = e.Message;            
            }  
            return _return;  
       }  
using System.Net;

        public static string domain2ip(string str)
        {
            string _return = "";
            try
            {
                IPHostEntry hostinfo = Dns.GetHostByName(str);
                IPAddress[] aryIP = hostinfo.AddressList;
                _return = aryIP[0].ToString();

            }
            catch (Exception e)
            {
                _return = e.Message;          
            }
            return _return;
        }

2 正则式匹配 作用：验证一个字串是否符合IP规则

using System.Text.RegularExpressions;  
  
            Match m = Regex.Match(ip, "(//d{1,3}//.){3}//d{1,3}");  
  
            if (m.Success)  
                data_ip = ip;//IP合法   
           else  
            {   //IP不合法   
                lab_prompt.Text = "服务器连接失败...";  
               this.btn_login.Enabled = false;  
            }