chap24.lst

Csharp2完全参考手册源代码 详细的说明可以在书里看到 该书是08年刚出炉很新鲜

listing 1
// Access the Internet. 
 
using System; 
using System.Net; 
using System.IO; 
 
class NetDemo {  
  public static void Main() { 
    int ch; 
 
    // First, create a WebRequest to a URI. 
    HttpWebRequest req = (HttpWebRequest) 
           WebRequest.Create("http://www.McGraw-Hill.com"); 
 
    // Next, send that request and return the response. 
    HttpWebResponse resp = (HttpWebResponse) 
           req.GetResponse(); 
 
    // From the response, obtain an input stream. 
    Stream istrm = resp.GetResponseStream(); 
 
 
    /* Now, read and display the html present at 
       the specified URI.  So you can see what is 
       being displayed, the data is shown 
       400 characters at a time.  After each 400 
       characters are displayed, you must press 
       ENTER to get the next 400. */ 
   
    for(int i=1; ; i++) { 
      ch =  istrm.ReadByte(); 
      if(ch == -1) break; 
      Console.Write((char) ch); 
      if((i%400)==0) { 
        Console.Write("\nPress Enter."); 
        Console.ReadLine(); 
      } 
    } 
 
    // Close the Response. This also closes istrm. 
    resp.Close(); 
  } 
}

listing 2
// Handle network exceptions. 
 
using System; 
using System.Net; 
using System.IO; 
 
class NetExcDemo {  
  public static void Main() { 
    int ch; 
 
    try { 
 
      // First, create a WebRequest to a URI. 
      HttpWebRequest req = (HttpWebRequest) 
             WebRequest.Create("http://www.McGraw-Hill.com"); 
 
      // Next, send that request and return the response. 
      HttpWebResponse resp = (HttpWebResponse) 
             req.GetResponse(); 
 
      // From the response, obtain an input stream. 
      Stream istrm = resp.GetResponseStream(); 
 
      /* Now, read and display the html present at 
         the specified URI.  So you can see what is 
         being displayed, the data is shown 
         400 characters at a time.  After each 400 
         characters are displayed, you must press 
         ENTER to get the next 400. */ 
   
      for(int i=1; ; i++) { 
        ch =  istrm.ReadByte(); 
        if(ch == -1) break; 
        Console.Write((char) ch); 
        if((i%400)==0) { 
          Console.Write("\nPress Enter."); 
          Console.ReadLine(); 
        } 
      } 
 
      // Close the Response. This also closes istrm. 
      resp.Close(); 
 
    } catch(WebException exc) { 
      Console.WriteLine("Network Error: " + exc.Message +  
                        "\nStatus code: " + exc.Status); 
    } catch(ProtocolViolationException exc) { 
      Console.WriteLine("Protocol Error: " + exc.Message); 
    } catch(UriFormatException exc) { 
      Console.WriteLine("URI Format Error: " + exc.Message); 
    } catch(NotSupportedException exc) { 
      Console.WriteLine("Unknown Protocol: " + exc.Message); 
    } catch(IOException exc) { 
      Console.WriteLine("I/O Error: " + exc.Message); 
    } catch(System.Security.SecurityException exc) { 
      Console.WriteLine("Security Exception: " + exc.Message); 
    } catch(InvalidOperationException exc) { 
      Console.WriteLine("Invalid Operation: " + exc.Message); 
    } 
  } 
}

listing 3
// Use Uri. 
 
using System; 
using System.Net; 
 
class UriDemo {  
  public static void Main() { 
 
    Uri sample = new Uri("http://MySite.com/somefile.txt?SomeQuery"); 
 
    Console.WriteLine("Host: " + sample.Host); 
    Console.WriteLine("Port: " + sample.Port); 
    Console.WriteLine("Scheme: " + sample.Scheme); 
    Console.WriteLine("Local Path: " + sample.LocalPath); 
    Console.WriteLine("Query: " + sample.Query); 
    Console.WriteLine("Path and query: " + sample.PathAndQuery); 
 
  } 
}

listing 4
// Examine the headers. 
 
using System; 
using System.Net; 
 
class HeaderDemo {  
  public static void Main() { 
 
    // Create a WebRequest to a URI. 
    HttpWebRequest req = (HttpWebRequest) 
           WebRequest.Create("http://www.McGraw-Hill.com"); 
 
    // Send that request and return the response. 
    HttpWebResponse resp = (HttpWebResponse) 
           req.GetResponse(); 
 
    // Obtain a list of the names. 
    string[] names = resp.Headers.AllKeys; 
 
    // Display the header name/value pairs. 
    Console.WriteLine("{0,-20}{1}\n", "Name", "Value"); 
    foreach(string n in names) 
      Console.WriteLine("{0,-20}{1}", n, resp.Headers[n]); 
 
    // Close the Response.  
    resp.Close(); 
  } 
}

listing 5
/* Examine Cookies. 
 
   To see what cookies a web site uses, 
   specify its name on the command line. 
   For example, if you call this program 
   CookieDemo, then 
  
     CookieDemo http://msn.com 
  
   displays the cookies associated with msn.com. 
*/ 
 
using System; 
using System.Net; 
 
class CookieDemo {  
  public static void Main(string[] args) { 
 
    if(args.Length != 1) { 
      Console.WriteLine("Usage: CookieDemo <uri>"); 
      return ; 
    } 
 
    // Create a WebRequest to the specified URI. 
    HttpWebRequest req = (HttpWebRequest) 
           WebRequest.Create(args[0]);  
 
    // Get an empty cookie container. 
    req.CookieContainer = new CookieContainer(); 
 
    // Send the request and return the response. 
    HttpWebResponse resp = (HttpWebResponse) 
           req.GetResponse(); 
 
    // Display the cookies. 
    Console.WriteLine("Number of cookies: " +  
                        resp.Cookies.Count); 
    Console.WriteLine("{0,-20}{1}", "Name", "Value"); 
 
    for(int i=0; i < resp.Cookies.Count; i++) 
      Console.WriteLine("{0, -20}{1}", 
                         resp.Cookies[i].Name, 
                         resp.Cookies[i].Value); 
 
    // Close the Response.  
    resp.Close(); 
  } 
}

listing 6
/* Use LastModified.  
  
   To see the date on which a web site was 
   last modified, enter its URI on the command 
   line. For example, if you call this program 
   LastModified, then see the date of last 
   modification for HerbSchildt.com enter 
   
     LastModifiedDemo http://HerbSchildt.com  
*/  
  
using System;  
using System.Net;  
  
class LastModifiedDemo {   
  public static void Main(string[] args) {  
  
    if(args.Length != 1) {  
      Console.WriteLine("Usage: LastModifiedDemo <uri>");  
      return ;  
    }  
  
    HttpWebRequest req = (HttpWebRequest)  
           WebRequest.Create(args[0]);  
  
    HttpWebResponse resp = (HttpWebResponse)  
           req.GetResponse();  
  
    Console.WriteLine("Last modified: " + resp.LastModified);  
  
    resp.Close();  
  }  
}

listing 7
/* MiniCrawler: A skeletal Web crawler. 
 
   Usage: 
     To start crawling, specify a starting 
     URI on the command line. For example, 
     to start at McGraw-Hill.com use this 
     command line: 
   
       MiniCrawler http://McGraw-Hill.com  
   
*/  
 
using System; 
using System.Net; 
using System.IO; 
 
class MiniCrawler {  
 
  // Find a link in a content string. 
  static string FindLink(string htmlstr,  
                         ref int startloc) { 
    int i; 
    int start, end; 
    string uri = null; 
    string lowcasestr = htmlstr.ToLower(); 
 
    i = lowcasestr.IndexOf("href=\"http", startloc); 
    if(i != -1) { 
      start = htmlstr.IndexOf('"', i) + 1; 
      end = htmlstr.IndexOf('"', start); 
      uri = htmlstr.Substring(start, end-start); 
      startloc = end; 
    } 
             
    return uri; 
  } 
 
  public static void Main(string[] args) { 
    string link = null; 
    string str; 
    string answer; 
 
    int curloc; // holds current location in response 
 
    if(args.Length != 1) { 
      Console.WriteLine("Usage: MiniCrawler <uri>"); 
      return ; 
    } 
 
    string uristr = args[0]; // holds current URI 
 
    try { 
 
      do { 
        Console.WriteLine("Linking to " + uristr); 
 
        // Create a WebRequest to the specified URI. 
        HttpWebRequest req = (HttpWebRequest) 
               WebRequest.Create(uristr); 
 
        uristr = null; // disallow further use of this URI 
 
        // Send that request and return the response. 
        HttpWebResponse resp = (HttpWebResponse) 
               req.GetResponse(); 
 
        // From the response, obtain an input stream. 
        Stream istrm = resp.GetResponseStream(); 
 
        // Wrap the input stream in a StreamReader. 
        StreamReader rdr = new StreamReader(istrm); 
 
        // Read in the entire page. 
        str = rdr.ReadToEnd(); 
 
        curloc = 0; 
        
        do { 
          // Find the next URI to link to. 
          link = FindLink(str, ref curloc); 
 
          if(link != null) { 
            Console.WriteLine("Link found: " + link); 
 
            Console.Write("Link, More, Quit?"); 
            answer = Console.ReadLine(); 
 
            if(string.Compare(answer, "L", true) == 0) { 
              uristr = string.Copy(link); 
              break; 
            } else if(string.Compare(answer, "Q", true) == 0) { 
              break; 
            } else if(string.Compare(answer, "M", true) == 0) { 
              Console.WriteLine("Searching for another link."); 
            } 
          } else { 
            Console.WriteLine("No link found."); 
            break; 
          } 
 
        } while(link.Length > 0); 
 
        // Close the Response. 
        resp.Close(); 
      } while(uristr != null); 
 
    } catch(WebException exc) { 
      Console.WriteLine("Network Error: " + exc.Message +  
                        "\nStatus code: " + exc.Status); 
    } catch(ProtocolViolationException exc) { 
      Console.WriteLine("Protocol Error: " + exc.Message); 
    } catch(UriFormatException exc) { 
      Console.WriteLine("URI Format Error: " + exc.Message); 
    } catch(NotSupportedException exc) { 
      Console.WriteLine("Unknown Protocol: " + exc.Message); 
    } catch(IOException exc) { 
      Console.WriteLine("I/O Error: " + exc.Message); 
    } 
 
    Console.WriteLine("Terminating MiniCrawler."); 
  } 
}

listing 8
// Use WebClient to download information into a file. 
 
using System; 
using System.Net; 
using System.IO; 
 
class WebClientDemo {  
  public static void Main() { 
    WebClient user = new WebClient(); 
    string uri = "http://www.McGraw-Hill.com"; 
    string fname = "data.txt"; 
     
    try { 
      Console.WriteLine("Downloading data from " + 
                        uri + " to " + fname); 
      user.DownloadFile(uri, fname); 
    } catch (WebException exc) { 
      Console.WriteLine(exc); 
    } 
 
    Console.WriteLine("Download complete."); 
  } 
}