方法1 比较推荐  

/// <summary> 
 
 /// 用HttpWebRequest取得网页源码 
 /// 对于带BOM的网页很有效，不管是什么编码都能正确识别 
 /// </summary> 
 /// <param name="url">网页地址" </param> 
 /// <returns>返回网页源文件</returns> 
 public static string GetHtmlSource2(string url)
 {
 //处理内容 
 string html = "";
 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
 request.Accept = "*/*"; //接受任意文件
 request.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.1.4322)"; // 模拟使用IE在浏览 http://www.52mvc.com
 request.AllowAutoRedirect = true;//是否允许302
 //request.CookieContainer = new CookieContainer();//cookie容器，
 request.Referer = url; //当前页面的引用
 
 
 HttpWebResponse response = (HttpWebResponse)request.GetResponse();
 Stream stream = response.GetResponseStream();
 StreamReader reader = new StreamReader(stream, Encoding.Default);
 html = reader.ReadToEnd();
 stream.Close();
 
 
 return html;
 }

方法2 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;
using System.Text;
using System.Net;

namespace MySql
{
 public class GetHttpData
 {
 public static string GetHttpData2(string Url)
 {
 string sException = null;
 string sRslt = null;
 WebResponse oWebRps = null;
 WebRequest oWebRqst = WebRequest.Create(Url);
 oWebRqst.Timeout = 50000;
 try
 {

 oWebRps = oWebRqst.GetResponse();

 }
 catch (WebException e)
 {
 sException = e.Message.ToString();
 }
 catch (Exception e)
 {
 sException = e.ToString();
 
 }
 finally
 {
 if (oWebRps != null)
 {
 
 StreamReader oStreamRd = new StreamReader(oWebRps.GetResponseStream(), Encoding.GetEncoding("utf-8"));
 sRslt = oStreamRd.ReadToEnd();
 oStreamRd.Close();
 oWebRps.Close();
 }
 }
 
 return sRslt;
 }
 
 }
}

方法3

public static string getHtml(string url, params string [] charSets)//url是要访问的网站地址，charSet是目标网页的编码，如果传入的是null或者""，那就自动分析网页的编码
 {
 try
 {
 string charSet = null;
 if (charSets.Length == 1) {
 charSet = charSets[0];
 }
 WebClient myWebClient = new WebClient(); //创建WebClient实例myWebClient
 // 需要注意的：
 //有的网页可能下不下来，有种种原因比如需要cookie,编码问题等等
 //这是就要具体问题具体分析比如在头部加入cookie
 // webclient.Headers.Add("Cookie", cookie);
 //这样可能需要一些重载方法。根据需要写就可以了
 
 
 //获取或设置用于对向 Internet 资源的请求进行身份验证的网络凭据。
 myWebClient.Credentials = CredentialCache.DefaultCredentials;
 //如果服务器要验证用户名,密码
 //NetworkCredential mycred = new NetworkCredential(struser, strpassword);
 //myWebClient.Credentials = mycred;
 //从资源下载数据并返回字节数组。（加@是因为网址中间有"/"符号）
 byte[] myDataBuffer = myWebClient.DownloadData(url);
 string strWebData = Encoding.Default.GetString(myDataBuffer);
 
 
 //获取网页字符编码描述信息
 Match charSetMatch = Regex.Match(strWebData, "<meta([^<]*)charset=([^<]*)\"", RegexOptions.IgnoreCase | RegexOptions.Multiline);
 string webCharSet = charSetMatch.Groups[2].Value;
 if (charSet == null || charSet == "")
 charSet = webCharSet;
 
 
 if (charSet != null && charSet != "" && Encoding.GetEncoding(charSet) != Encoding.Default)
 {
 strWebData = Encoding.GetEncoding(charSet).GetString(myDataBuffer);
 }
 else {
 strWebData = Encoding.GetEncoding("utf-8").GetString(myDataBuffer);
 }
 return strWebData;
 }
 catch (Exception e) { return ""; }
 }

asp.net 获取网页源文件的方法

有时候我们需要获取 网页源文件，所以用以下这个方法很容易完成任务！

private string GetStringByUrl(string strUrl) 
{ 
 WebRequest wrt = WebRequest.Create(strUrl); 
 WebResponse wrse = wrt.GetResponse(); 
 Stream strM = wrse.GetResponseStream(); 
 StreamReader SR = new StreamReader(strM, Encoding.GetEncoding("gb2312")); 
 string strallstrm = SR.ReadToEnd(); 
 return strallstrm; 
} 

只要传入要下载网页的地址就OK了！
通过这个方法做个源码导出:

private string SaveHTML() 
 { 
string str = RenderPage("Default2.aspx"); 
 Response.ContentEncoding = System.Text.Encoding.GetEncoding("UTF-8"); //解决中文乱码 
 Response.AddHeader("Content-Disposition","attachment;filename=index.html"); //解决中文文件名乱码 
 Response.AddHeader("Content-length",str.Length.ToString()); 
 Response.Write(str); 
 Response.End(); 
｝