if (args.Length == 0)
{
    Console.WriteLine("must specify a URL!");
    return;
}
string server = args[0];

// Create the web request 
HttpWebRequest myHttpWebRequest = 
    (HttpWebRequest) WebRequest.Create(server);
myHttpWebRequest.Timeout = 1000;
// Get the associated response for the above request.
HttpWebResponse myHttpWebResponse = 
    (HttpWebResponse) myHttpWebRequest.GetResponse();

// Get the headers associated with the response.
WebHeaderCollection myWebHeaderCollection = 
    myHttpWebResponse.Headers;

for(int i = 0; i < myWebHeaderCollection.Count; i++)
{
    String header = myWebHeaderCollection.GetKey(i);
    String[] values = 
        myWebHeaderCollection.GetValues(header);
    if(values.Length > 0) 
    {
        Console.WriteLine("The values of {0} header are : "
                         , header);
        for(int j = 0; j < values.Length; j++) 
            Console.WriteLine("\t{0}", values[j]);
    }
    else
        Console.WriteLine("There is no value associated" +
            "with the header");
}
Console.WriteLine("");

// Get the headers again, using new properties (Keys, 
// AllKeys, Clear) and methods (Get and GetKey)

string[] headers = myWebHeaderCollection.AllKeys;

// enumerate through the header collection.
foreach (string s in headers)
{
    Console.WriteLine("Header {0}, value {1}",
        s,
        myWebHeaderCollection.Get(s) );
}

Console.WriteLine("");

// show the use of Get(Int32) and GetValue(Int32)
if (myWebHeaderCollection.Count > 0)
{
    // get the name and value of the first header
    int index=0;
    Console.WriteLine("Header {0}: name {1}, value {2}",
        index, 
        myWebHeaderCollection.GetKey(index),
        myWebHeaderCollection.Get(index));
}

myWebHeaderCollection.Clear();

myHttpWebResponse.Close();

//引入命名空间
using System;
using System.IO;
using System.Net;

public class TryURL {
  public static void Main(String [] args) {
    WebClient client = new WebClient();
    client.BaseAddress = "http://www.java2s.com";
    client.DownloadFile("www.java2s.com", "index.htm");
    StreamReader input =new StreamReader(client.OpenRead("index.htm"));
    Console.WriteLine(input.ReadToEnd());
    Console.WriteLine
      ("Request header count: {0}", client.Headers.Count);
    WebHeaderCollection header = client.ResponseHeaders;
    Console.WriteLine
      ("Response header count: {0}", header.Count);
    for (int i = 0; i < header.Count; i++)
      Console.WriteLine("   {0} : {1}", 
                          header.GetKey(i), header[i]);
    input.Close();
  }
}