截取网页代码，并查找字符串是否存在

 1        public string GetPage(string url, string postData)
 2        {
 3            Stream outstream = null;
 4            Stream instream = null;
 5            StreamReader sr = null;
 6            HttpWebResponse response = null;
 7            HttpWebRequest request = null;
 8            Encoding encoding = Encoding.UTF8;
 9            byte[] data = encoding.GetBytes(postData);
10            // 准备请求Encoding
11            try
12            {
13                // 设置参数
14                request = WebRequest.Create(url) as HttpWebRequest;
15                CookieContainer cookieContainer = new CookieContainer();
16                request.CookieContainer = cookieContainer;
17                request.AllowAutoRedirect = true;
18                request.Method = "POST";
19                request.ContentType = "application/x-www-form-urlencoded";
20                request.ContentLength = data.Length;
21                outstream = request.GetRequestStream();
22                outstream.Write(data, 0, data.Length);
23                outstream.Close();
24                //发送请求并获取相应回应数据
25                response = request.GetResponse() as HttpWebResponse;
26                //直到request.GetResponse()程序才开始向目标网页发送Post请求
27                instream = response.GetResponseStream();
28                sr = new StreamReader(instream, encoding);
29                //返回结果网页（html）代码
30                string content = sr.ReadToEnd();
31                
32                return content.ToString();
33            }
34            catch (Exception ex)
35            {
36                string err = ex.Message;
37                return string.Empty;
38            }
39        }
40        public bool ConpareUrl(string s,string sUrl)
41        {
42            String Pattern = GetPage(sUrl,"a"); 
43            Regex r = new Regex(s);
44            Match m = r.Match(Pattern);
45            if(m.Success)
46            {
47                return true;
48            }
49            else
50            {
51                return false;
52            }
53        }
54