获取指定网页的远程资源可使用 WebClient、WebRequest、HttpWebRequest 三种方式来实现。当然也可使用webBrowse，webBrowse不做介绍。

　　通过 System.Net 名称空间下 WebClient 类下载文件。

//通过WebClient下载网页的源码            string url = "http://www.example.com";         System.Net.WebClient client = new System.Net.WebClient();        client.Encoding = System.Text.Encoding.UTF8;        string strHtml = client.DownloadString(url);

 

 综合实例：

using System;using System.Text;using System.IO;using System.Net;namespace SnapUtility{    public class ServerResourceHelper    {        /// 
        /// 通过WebClient获取远程资源        /// 
        ///         /// 
             public static string GetByWebClient(string url)        {            string strReturn = null;            WebClient client = new WebClient();            //client.Headers.Add(HttpRequestHeader.Accept, @"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8");            //client.Headers.Add(HttpRequestHeader.Referer, null);            //client.Headers.Add(HttpRequestHeader.UserAgent, @" Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36");            //client.Headers.Add(HttpRequestHeader.ContentType, "application/octet-stream");                        string strExtension = Path.GetExtension(url); //扩展名            if (String.IsNullOrEmpty(strExtension))            {                Stream stream = client.OpenRead(url);                StreamReader streamReader = new StreamReader(stream, Encoding.GetEncoding("utf-8"));                strReturn = streamReader.ReadToEnd();                streamReader.Close();                stream.Close();            }            else            {                string path = "../WebSnap/DownLoad/";                path = System.Web.HttpContext.Current.Server.MapPath(path);                //自动创建文件夹                if (!Directory.Exists(path))                {                    Directory.CreateDirectory(path);                }                path += DateTime.Now.ToString("hhmmss") + strExtension;                client.DownloadFile(new Uri(url), path);            }            client.Dispose();            return strReturn;        }        /// 
        /// 通过WebRequest获取远程资源        /// 
        ///         /// 
             public static string GetByWebRequest(string url)        {            string strReturn = null;            Uri uri = new Uri(url);            WebRequest request = WebRequest.Create(uri);            WebResponse response = request.GetResponse();            Stream stream = response.GetResponseStream();            string strExtension = Path.GetExtension(url); //扩展名            if (String.IsNullOrEmpty(strExtension))            {                StreamReader streamReader = new StreamReader(stream, Encoding.GetEncoding("utf-8"));                strReturn = streamReader.ReadToEnd();                streamReader.Close();                stream.Close();                response.Close();            }            else            {                string fileName = DateTime.Now.ToString("hhmmss") + strExtension;                long length = response.ContentLength;                strReturn = SaveFile(ref stream, fileName, length);            }            return strReturn;        }        /// 
        /// 通过WebRequest的Http特定实现获取远程资源        /// 
        /// 远程地址        /// 
             public static string GetByHttpWebRequest(string url)        {            string strReturn = null;            Uri uri = new Uri(url);            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);            HttpWebResponse response = (HttpWebResponse)request.GetResponse();            Stream stream = response.GetResponseStream();            string strExtension = Path.GetExtension(url); //扩展名            if (String.IsNullOrEmpty(strExtension))            {                StreamReader streamReader = new StreamReader(stream, System.Text.Encoding.GetEncoding("utf-8"));                strReturn = streamReader.ReadToEnd();                streamReader.Close();                stream.Close();                response.Close();            }            else            {                string fileName = DateTime.Now.ToString("hhmmss") + strExtension;                long length = response.ContentLength;                strReturn = SaveFile(ref stream, fileName, length);            }            return strReturn;        }        /// 
        /// FileStream保存文件        /// 
        ///         private static string SaveFile(ref Stream stream, string fileName, long length)        {            byte[] buffer = new byte[length];            stream.Read(buffer, 0, buffer.Length);            stream.Close();            string path = AppDomain.CurrentDomain.BaseDirectory + "DownLoad\\" + fileName;            FileStream fileStream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write);            fileStream.Write(buffer, 0, buffer.Length);            fileStream.Flush();            fileStream.Close();            return path;        }        /// 
        /// 保存图片        /// 
        ///         private static string SavePicture(ref Stream stream, string fileName)        {            System.Drawing.Image image = System.Drawing.Image.FromStream(stream);            stream.Close();            string path = "../WebSnap/DownLoad/";            path = System.Web.HttpContext.Current.Server.MapPath(path);            //自动创建文件夹            if (!Directory.Exists(path))            {                Directory.CreateDirectory(path);            }            path += fileName;            image.Save(path, System.Drawing.Imaging.ImageFormat.Png);            image.Dispose(); //释放资源            return path;        }    }}

 

注意：

“utf-8”应与指定网页的编码对应。

可以看到HttpWebRequest 方式最复杂，但确提供了更多的选择性。

有的网站检测客户端的UserAgent！如163