在C# Winform 应用程序中，获取某网页的源文件，可以用以下方法：
首先引入名称空间using System.IO;
using ;
WebClient MyWebClient = new WebClient();
MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于向Internet资源的请求进行身份验证的网络凭据
Byte[] pageData = MyWebClient.DownloadData("");
//string pageHtml = Encoding.Default.GetString(pageData);
FileStream file = new FileStream("C:\\test.html", FileMode.Create);
file.Write(pageData, 0, pageData.Length);
附，c# 获取网页源码的代码举例。
C# 获取指定网页HTML原代码可使用：WebClient WebRequest HttpWebRequest 三种方式。
当然也可使用webBrowse，有兴趣的朋友，可以自己研究下。
1，WebClient方式
private string GetWebClient(string url)
{
string strHTML = "";
WebClient myWebClient = new WebClient();
Stream myStream = myWebClient.OpenRead(url);
StreamReader sr = new StreamReader(myStream, System.Text.Encoding.GetEncoding("utf-8"));
strHTML = sr.ReadToEnd();
myStream.Close();
return strHTML;
}
2，WebRequest方式
private string GetWebRequest(string url)
{
Uri uri = new Uri(url);
WebRequest myReq = WebRequest.Create(uri);
WebResponse result = myReq.GetResponse();
Stream receviceStream = result.GetResponseStream();
StreamReader readerOfStream = new StreamReader(receviceStream, System.Text.Encoding.GetEncoding("utf-8"));
string strHTML = readerOfStream.ReadToEnd();
readerOfStream.Close();
receviceStream.Close();
result.Close();
return strHTML;
}
3，HttpWebRequest方式
private string GetHttpWebRequest(string url)
{
Uri uri = new Uri(url);
HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(uri);
myReq.UserAgent = "User-Agent:Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705";
myReq.Accept = "*/*";
myReq.KeepAlive = true;
myReq.Headers.Add("Accept-Language", "zh-cn,en-us;q=0.5");
HttpWebResponse result = (HttpWebResponse)myReq.GetResponse();
Stream receviceStream = result.GetResponseStream();
StreamReader readerOfStream = new StreamReader(receviceStream, System.Text.Encoding.GetEncoding("utf-8"));
string strHTML = readerOfStream.ReadToEnd();
readerOfStream.Close();
receviceStream.Close();
result.Close();
return strHTML;
}
注意：“utf-8”应与指定网页的编码对应。
总结
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，如果使用WebClient WebRequest方式获取，将获取到的是错误提示页面的内容。
HttpWebRequest没有这个问题。
测试环境：WIN + VS + C# + winForm
