Professional ASP.NET 3.5 in C# and Visual Basic Part 123 pps

Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1180 Chapter 25: File I/O and Streams { #region IHttpModule Members void IHttpModule.Dispose() { throw new Exception("The method or operation is not implemented."); } void IHttpModule.Init(HttpApplication context) { context.BeginRequest += new EventHandler(context_BeginRequest); } void context_BeginRequest(object sender, EventArgs e) { HttpApplication app = (HttpApplication)sender; //Get the Accept-Encoding HTTP header from the request. //The requesting browser sends this header which we will use // to determine if it supports compression, and if so, what type // of compression algorithm it supports string encodings = app.Request.Headers.Get("Accept-Encoding"); if (encodings == null) return; Stream s = app.Response.Filter; encodings = encodings.ToLower(); if (encodings.Contains("gzip")) { app.Response.Filter = new GZipStream(s, CompressionMode.Compress); app.Response.AppendHeader("Content-Encoding", "gzip"); app.Context.Trace.Warn("GZIP Compression on"); } else { app.Response.Filter = new DeflateStream(s, CompressionMode.Compress); app.Response.AppendHeader("Content-Encoding", "deflate"); app.Context.Trace.Warn("Deflate Compression on"); } } #endregion } } After you create and b uild the module, add the assembly to your Web site’s Bin directory. After that’s done, you let your Web application know that it should use the HttpModule when it runs. Do this by adding the module to the web.config file. Listing 25-23 shows the nodes to add to the web.config system.web configuration section. 1180 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1181 Chapter 25: File I/O and Streams Listing 25-23: Adding an HttpCompression module to the web.config < httpModules > < add name="HttpCompressionModule" type="Wrox.Demo.Compression.CompressionModule, HttpCompressionModule"/ > < /httpModules > < trace enabled="true" / > Notice that one other change you are making is to enable page tracing. You use this to demonstrate that the page is actually being compressed. When you run the page, you should see the trace output shown in Figure 25-14. Notice a new entry under the trace information showing that the GZip compression has been enabled on this page. Figure 25-14 Working with Serial Ports Also introduced in the .NET 2.0 Framework was the System.IO.Ports namespace. This namespace contains classes that enable you to work with and communicate through serial ports. .NET provides a SerialPort component that you can add to the Component Designer of your Web page. Adding this component enables your application to communicate via the serial port. Listing 25-24 shows how to write some text to the serial port. 1181 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1182 Chapter 25: File I/O and Streams Listing 25-24: Writing text to the serial port VB < script runat="server" > Dim SerialPort1 As New System.IO.Ports.SerialPort() Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Me.SerialPort1.PortName = "COM1" If (Not Me.SerialPort1.IsOpen()) Then Me.SerialPort1.Open() End If Me.SerialPort1.Write("Hello World") Me.SerialPort1.Close() End Sub < /script > C# < script runat="server" > System.IO.Ports.SerialPort SerialPort1 = new System.IO.Ports.SerialPort(); protected void Page_Load(object sender, EventArgs e) { this.SerialPort1.PortName = "COM1"; if (!this.SerialPort1.IsOpen) { this.SerialPort1.Open(); } this.SerialPort1.Write("Hello World"); this.SerialPort1.Close(); } < /script > This code simply attempts to open the serial port COM1 and write a bit of text. The SerialPort component gives you control over most aspects of the serial port, including baud rate, parity, and stop bits. Network Communications Finally, this chapter takes you beyond your own systems and talks about how you can use the .NET Framework to communicate with other systems. The .NET Framework contains a rich set of classes in the System.Net namespace that allow you to communicate over a network using a variety of protocols and communications layers. You can perform all types of actions, from DNS resolution to programmatic HTTP Posts to sending e-mail through SMTP. 1182 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1183 Chapter 25: File I/O and Streams WebRequest and WebResponse The first series of classes to discuss are the WebRequest and WebResponse classes. You can use these two classes to develop applications that can make a request to a Uniform Resource Identifier (URI) and receive a response from that resource. The .NET Framework provides three derivatives of the WebRequest and WebResponse classes, each designed to communicate to a specific type of end point via HTTP, FTP, and file:// protocols. HttpWebRequest and HttpWebResponse The first pair of classes are the HttpWebRequest and HttpWebResponse classes. As you can probably guess based on their names, these two classes are designed to communicate using the HTTP protocol. Perhaps the most famous use of the HttpWebRequest and HttpWebResponse classes is t o write applications that can make requests to other Web pages via HTTP and parse the resulting text to extract data. This is known as screen scraping. For an example of using the HttpWebRequest and HttpWebResponse classes to screen scrape, you can use the following code to build a Web page that will serve as a simple Web browser. You also learn how another Web page can be displayed inside of yours using an HttpWebRequest .Inthisexample,you scrape the wrox.com home page a nd display it in a panel on your Web page. Listing 25-25 shows the code. Listing 25-25: Using an HttpWebRequest to retrieve a Web page VB < %@ Page Language="VB" % > < %@ Import Namespace=System.IO % > < %@ Import Namespace=System.Net % > < script runat="server" > Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Dim uri As New Uri("http://www.wrox.com/") If (uri.Scheme = uri.UriSchemeHttp) Then Dim request As HttpWebRequest = HttpWebRequest.Create(uri) request.Method = WebRequestMethods.Http.Get Dim response As HttpWebResponse = request.GetResponse() Dim reader As New StreamReader(response.GetResponseStream()) Dim tmp As String = reader.ReadToEnd() response.Close() Me.Panel1.GroupingText = tmp End If End Sub < /script > < html xmlns="http://www.w3.org/1999/xhtml" > < head runat="server" > < title > Untitled Page < /title > < /head > < body > < form id="form1" runat="server" > < div > Continued 1183 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1184 Chapter 25: File I/O and Streams < p > This is the wrox.com website: < /p > < asp:Panel ID="Panel1" runat="server" Height="355px" Width="480px" ScrollBars=Auto > < /asp:Panel > < /div > < /form > < /body > < /html > C# < script runat="server" > protected void Page_Load(object sender, EventArgs e) { Uri uri = new Uri("http://www.wrox.com/"); if (uri.Scheme == Uri.UriSchemeHttp) { HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create( uri ); request.Method = WebRequestMethods.Http.Get; HttpWebResponse response = (HttpWebResponse)request.GetResponse(); StreamReader reader = new StreamReader(response.GetResponseStream()); string tmp = reader.ReadToEnd(); response.Close(); this.Panel1.GroupingText = tmp; } } < /script > Figure 25-15 shows what the Web page look likes when you execute the code in Listing 25-25. The Http- WebRequest to the Wrox.com home page returns a string containing the scraped HTML. The sample assigns the value of this string to the GroupingText property of the Panel control. When the final page is rendered, the browser renders the HTML that was scraped as literal content on the page. Oneotheruseofthe HttpWebRequest and HttpWebResponse classes is to programmatically post data to another Web page, as shown in Listing 25-26. Listing 25-26: Using an HttpWebRequest to post data to a remote Web page VB < %@ Page Language="VB" % > < %@ Import Namespace=System.IO % > < %@ Import Namespace=System.Net % > < script runat="server" > Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Dim uri As New Uri("http://www.amazon.com/" & _ "exec/obidos/search-handle-form/102-5194535-6807312") Dim data As String = "field-keywords=Professional ASP.NET 3.5" If (uri.Scheme = uri.UriSchemeHttp) Then Dim request As HttpWebRequest = HttpWebRequest.Create(uri) Continued 1184 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1185 Chapter 25: File I/O and Streams request.Method = WebRequestMethods.Http.Post request.ContentLength = data.Length request.ContentType = "application/x-www-form-urlencoded" Dim writer As New StreamWriter(request.GetRequestStream()) writer.Write(data) writer.Close() Dim response As HttpWebResponse = request.GetResponse() Dim reader As New StreamReader(response.GetResponseStream()) Dim tmp As String = reader.ReadToEnd() response.Close() Me.Panel1.GroupingText = tmp End If End Sub < /script > < html xmlns="http://www.w3.org/1999/xhtml" > < head runat="server" > < title > Untitled Page < /title > < /head > < body > < form id="form1" runat="server" > < div > < asp:Panel ID="Panel1" runat="server" Height="355px" Width="480px" ScrollBars=Auto > < /asp:Panel > < /div > < /form > < /body > < /html > C# < script runat="server" > protected void Page_Load(object sender, EventArgs e) { Uri uri = new Uri("http://www.amazon.com/" + "exec/obidos/search-handle-form/102-5194535-6807312"); string data = "field-keywords=Professional ASP.NET 3.5"; if (uri.Scheme == Uri.UriSchemeHttp) { HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(uri); request.Method = WebRequestMethods.Http.Post; request.ContentLength = data.Length; request.ContentType = "application/x-www-form-urlencoded"; StreamWriter writer = new StreamWriter( request.GetRequestStream() ); writer.Write(data); writer.Close(); HttpWebResponse response = (HttpWebResponse)request.GetResponse(); Continued 1185 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1186 Chapter 25: File I/O and Streams StreamReader reader = new StreamReader(response.GetResponseStream()); string tmp = reader.ReadToEnd(); response.Close(); this.Panel1.GroupingText = tmp; } } < /script > Figure 25-15 You can see that the preceding code posts a search query to Amazon.com and receives the HTML as the response. As in the example shown earlier in Listing 25-25, you can simply use a Panel to display the resulting text as HTML. The results of the query are shown in Figure 25-16. FtpWebRequest and FtpWebResponse The next pair of classes are the FtpWebRequest and FtpWebResponse classes. These two classes were new additions to the .NET 2.0 Framework, and they make it easy to execute File Transfer Protocol (FTP) commands from your Web page. Using these classes, it is now possible to implement an entire FTP client right from your Web application. Listing 25-27 shows an e xample of downloading a text file from the public Microsoft.com FTP site. (See Figure 25-17.) 1186 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1187 Chapter 25: File I/O and Streams Figure 25-16 Figure 25-17 1187 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1188 Chapter 25: File I/O and Streams Listing 25-27: Using an FtpWebRequest to download a file from an FTP site VB < %@ Page Language="VB" % > < %@ Import Namespace=System.IO % > < %@ Import Namespace=System.Net % > < script runat="server" > Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Dim uri As New Uri("ftp://ftp.microsoft.com/SoftLib/ReadMe.txt") If (uri.Scheme = uri.UriSchemeFtp) Then Dim request As FtpWebRequest = FtpWebRequest.Create(uri) request.Method = WebRequestMethods.Ftp.DownloadFile Dim response As FtpWebResponse = request.GetResponse() Dim reader As New StreamReader(response.GetResponseStream()) Dim tmp As String = reader.ReadToEnd() response.Close() Me.Panel1.GroupingText = tmp End If End Sub < /script > < html xmlns="http://www.w3.org/1999/xhtml" > < head runat="server" > < title > Using FTP from an ASP.NET webpage < /title > < /head > < body > < form id="form1" runat="server" > < div > < div runat="server" id="ftpContent" style="overflow:scroll; height: 260px; width: 450px;" > < /div > < /div > < /form > < /body > < /html > C# < script runat="server" > protected void Page_Load(object sender, EventArgs e) { Uri uri = new Uri("ftp://ftp.microsoft.com/SoftLib/ReadMe.txt "); if (uri.Scheme == Uri.UriSchemeFtp) { FtpWebRequest request = (FtpWebRequest)FtpWebRequest.Create(uri); request.Method = WebRequestMethods.Ftp.DownloadFile; FtpWebResponse response = (FtpWebResponse)request.GetResponse(); StreamReader reader = new StreamReader(response.GetResponseStream()); Continued 1188 Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1189 Chapter 25: File I/O and Streams string tmp = reader.ReadToEnd(); response.Close(); this.Panel1.GroupingText = tmp; } } < /script > FileWebRequest and FileWebResponse Next, look at the FileWebRequest and FileWebResponse classes. These classes provide a file system implementation of the WebRequest and WebResponse classes and are designed to make it easy to transfer files using the file:// protocol, as shown in Listing 25-28. Listing 25-28: Using the FileWebRequest to write to a remote file VB Dim uri As New Uri("file://DEMOXP/Documents/lorum.txt") If (uri.Scheme = uri.UriSchemeFile) Then Dim request As System.Net.FileWebRequest = _ System.Net.FileWebRequest.Create(uri) Dim response As System.Net.FileWebResponse = request.GetResponse() Dim reader As New System.IO.StreamReader(response.GetResponseStream()) Dim tmp As String = reader.ReadToEnd() response.Close() End If C# Uri uri = new Uri("file://DEMOXP/Documents/lorum.txt "); if (uri.Scheme == Uri.UriSchemeFile) { System.Net.FileWebRequest request = (System.Net.FileWebRequest)System.Net.FileWebRequest.Create(uri); System.Net.FileWebResponse response = (System.Net.FileWebResponse)request.GetResponse(); System.IO.StreamReader reader = new System.IO.StreamReader(response.GetResponseStream()); string tmp = reader.ReadToEnd(); response.Close(); } In this listing, we are requesting the lorum.txt file that exists in the Documents folder on the DEMOXP machine on our local network. Sending Mail Finally, consider a feature common to many Web applications — the capability to send e-mail from a Web page. The capability to send m ail was part of the 1.0 Framework and located in the System.Web.Mail namespace. In the 2.0 Framework, this functionality was enhanced and moved to the System.Net.Mail namespace. Listing 25-29 shows an example of sending an e-mail. 1189 . Uri("http://www.amazon.com/" & _ "exec/obidos/search-handle-form/102 -51 94 53 5 -680 731 2") Dim data As String = "field-keywords =Professional ASP. NET 3. 5& quot; If (uri.Scheme = uri.UriSchemeHttp). displayed inside of yours using an HttpWebRequest .Inthisexample,you scrape the wrox.com home page a nd display it in a panel on your Web page. Listing 25- 25 shows the code. Listing 25- 25: Using an. Uri("http://www.amazon.com/" + "exec/obidos/search-handle-form/102 -51 94 53 5 -680 731 2"); string data = "field-keywords =Professional ASP. NET 3. 5& quot;; if (uri.Scheme == Uri.UriSchemeHttp) { HttpWebRequest