asp.net 生成静态页时如何过滤掉viewstate

public static string GetSourceTextByUrl(string url)
{
WebRequest request = WebRequest.Create(url);
request.Timeout = 200000;//20秒超时
WebResponse response = request.GetResponse();
Stream resStream = response.GetResponseStream();
StreamReader sr = new StreamReader(resStream);
string tempstr = sr.ReadToEnd();

Regex r1 = new Regex("<input type="hidden" name="__EVENTTARGET".*/>", RegexOptions.IgnoreCase);
Regex r2 = new Regex("<input type="hidden" name="__EVENTARGUMENT".*/>", RegexOptions.IgnoreCase);
Regex r3 = new Regex("<input type="hidden" name="__VIEWSTATE".*/>", RegexOptions.IgnoreCase);
//过滤<form>代码
Regex r4 = new Regex("<form name="aspnetForm".*id="aspnetForm">", RegexOptions.IgnoreCase);
Regex r5 = new Regex("</form>");
tempstr = r1.Replace(tempstr, "");
tempstr = r2.Replace(tempstr, "");
tempstr = r3.Replace(tempstr, "");
tempstr = r4.Replace(tempstr, "");
tempstr = r5.Replace(tempstr, "");

return tempstr;
}