C#快速获取指定网页源码的几种方式，并通过字符串截取函数 或 正则 取指定内容(IP)

//只获取网页源码开始到标题位目的进行测试
//第一种方式经过测试，稍微快点
 string url = "http://www.ip.cn";
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Method = "GET";
            req.ContentType = "application/x-www-form-urlencoded";
            HttpWebResponse res = (HttpWebResponse)req.GetResponse();
            Stream ReceiveStream = res.GetResponseStream();
            Encoding encode = System.Text.Encoding.UTF8;
            StreamReader sr = new StreamReader(ReceiveStream, encode);

            string strResult = "";
            Char[] read = new Char[256];
            int count = sr.Read(read, 0, 256);
            while (count > 0)
            {
                String str = new String(read, 0, count);
                strResult += str;
                count = sr.Read(read, 0, 256);
                if (strResult.IndexOf("</title>") != -1)
                {
                    break;
                }
            }
            textBoxTest.Text = strResult;


//第二种获取网页源码

WebClient MyClient = new WebClient();
MyClient.Credentials = CredentialCache.DefaultCredentials;
MyClient.Headers.Add("Host", "www.kuwo.cn");
MyClient.Headers.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");
Byte[] pageData = MyClient.DownloadData(url);
//string pageHtml = Encoding.Default.GetString(pageData);  //GB2312  
string pageHtml = Encoding.UTF8.GetString(pageData); //UTF-8



//字符串截取，从网页源码中截取 两字符串中间信息
private string GetStr(string TxtStr, string FirstStr, string SecondStr)
        {
            if (FirstStr.IndexOf(SecondStr, 0) != -1)
                return "";
            int FirstSite = TxtStr.IndexOf(FirstStr, 0);
            int SecondSite = TxtStr.IndexOf(SecondStr, FirstSite + 1);
            if (FirstSite == -1 || SecondSite == -1)
                return "";
            return TxtStr.Substring(FirstSite + FirstStr.Length, SecondSite - FirstSite - FirstStr.Length);
        }

//正则截取字符串 A.B之间
string title2 = Regex.Match(title, "(?<="+"A"+").*?(?="+"B"+")").Value;
//Regex.Match(sUrl, "(?<=A).*?(?=B)").Value;

 //自定义函数
private string MyGetTitle(string url, string endTag, string startStr, string endStr)
        {
            try
            {
                //HttpWebRequest类继承于WebRequest，并没有自己的构造函数，需通过WebRequest的Creat方法 建立，并进行强制的类型转换
                HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
                req.Method = "GET";
                req.ContentType = "text/html;charset=UTF-8";
                //通过HttpWebRequest的GetResponse()方法建立HttpWebResponse,强制类型转换
                HttpWebResponse res = (HttpWebResponse)req.GetResponse();
                //若成功取得网页的内容，则以System.IO.Stream形式返回，
                //若失败则产生ProtoclViolationException错 误。
                //在此正确的做法应将以下的代码放到一个try块中处理。这里简单处理
                Stream ReceiveStream = res.GetResponseStream();
                //返回的内容是Stream形式的，所以可以利用StreamReader类获取GetResponseStream的内容,
                //并以StreamReader类的Read方法依次读取网页源程序代码每一行的内容，直至行尾（读取的编码格式：UTF8） 
                StreamReader sr = new StreamReader(ReceiveStream, Encoding.UTF8);
                string strResult = "";
                Char[] read = new Char[256];
                //Read(char[] buffer,int index,int count);
                //从文件流的第index个位置开始读，到count个字符，把它们存到buffer中，
                //然后返回一个正数，内部指针后移一位，保证下次从新的位置开始读。
                int count = sr.Read(read, 0, 256);
                while (count > 0)
                {
                    String str = new String(read, 0, count);
                    strResult += str;
                    count = sr.Read(read, 0, 256);
                    if (strResult.IndexOf(endTag) != -1) break;
                }
                res.Close();
                ReceiveStream.Dispose();
                return Regex.Match(strResult, "(?<=" + startStr + ").*?(?=" + endStr + ")").Value;
            }
            catch (Exception ex)
            {
                LogAdd(ListBoxDownLog, "异常：" + ex.Message);
                throw;
            }

        }