如何抓取网站上的数据

WebClient wc = new WebClient();
string str = wc.DownloadString("需要抓取的url");
String str1 = "正则表达式";
MatchCollection mc = Regex.Matches(str, str1);

//循环获取数据，操作

for (int i = 0; i < mc.Count; i++)
            {
                Match m = mc[i];
.....
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