Guestbook for ASP.NET - The Code Project - AS...

Contents
IntroductionDatabaseApplicationSigningViewingConclusionFaced Problems
Introduction
It is a project permitting people to sign a guestbook on a website. The project is built in two parts:
Signing the guestbook. Viewing the guestbook.
Database
The guestbook will be stored in an XML file on the server, named guestbook.xml. The encoding of the XML file is changed to ISO-8859-1 to be able to handle special characters. Here is the structure of the XML file:
Laurent Kemp?t;/name>Tech HeadIllzach, FranceFirst to sign the guestbook ;)Thursday, May 30, 2002 - 10:29 AM
You will be prompted to enter the following information:
Name E-Mail Homepage title Homepage URL Location Comments PRIVATE - I only want the web site owner to see my email
Application
To be free to change the way the guestbook is displayed, it is needed to separate the coding from the data. To achieve this requirement, I chose to use XSLT to transform the XML file to an HTML file returned to the client.
Signing
The page that will permit people to sign the guestbook is the Web Form called 'Sign.aspx'. This page will require that the user fill some textboxes with information to be displayed on the guestbook. To be able to validate the information, we use RequiredFieldValidator. We also use a RegularExpressionValidator to validate the email address.
When the guest has filled all his information, he presses the Continue button and the page gets back the event in the method ButtonContinue_Click. The method loads the XML database, retrieves the information entered by the guest and adds them at the beginning of the XML file. Then the new database is saved on the server disk and the guest is redirected to the view page.
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private void ButtonContinue_Click(object sender, System.EventArgs e){//Load guestbook databaseXmlDocument xmldoc = new XmlDocument();xmldoc.Load( Server.MapPath("guestbook.xml") );//Get private statusstring strPrivate;if ( CheckBoxPrivate.Checked )strPrivate = "yes";elsestrPrivate = "no";//Create a new elementXmlElement elem = xmldoc.CreateElement("guest");elem.SetAttribute("private", strPrivate);//Add the new guest as the first nodexmldoc.DocumentElement.PrependChild(elem);addTextElement( xmldoc, elem, "name", TextBoxName.Text );addTextElement( xmldoc, elem, "email", TextBoxEMail.Text );addTextElement( xmldoc, elem, "homepage", TextBoxHomepageTitle.Text );XmlAttribute newAttr = xmldoc.CreateAttribute("url");newAttr.Value = TextBoxHomepageURL.Text;elem.LastChild.Attributes.Append( newAttr );addTextElement( xmldoc, elem, "location", TextBoxLocation.Text );addTextElement( xmldoc, elem, "comment", TextBoxComments.Text );//Write datestring strDate = DateTime.Now.ToLongDateString() +" - " +DateTime.Now.ToLongTimeString();addTextElement( xmldoc, elem, "date", strDate );xmldoc.Save( Server.MapPath("guestbook.xml") );Response.Redirect("view.aspx");}
We use the method addTextElement to build the new guest entry into the database:
private void addTextElement( XmlDocument doc, XmlElement nodeParent,string strTag, string strValue ){XmlElement nodeElem = doc.CreateElement( strTag );XmlText nodeText = doc.CreateTextNode( strValue );nodeParent.AppendChild( nodeElem );nodeElem.AppendChild( nodeText );}Viewing
To view all guestbook entries, we add another Web Form called 'View.aspx' to the project. In the Page_Load method of the page, we load the XML database and the XSLT file. We do the transformation and output the result in a Literal Web Form control.
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private void Page_Load(object sender, System.EventArgs e){//Load guestbook database from the xml fileXmlDocument doc = new XmlDocument( );doc.Load( Server.MapPath("guestbook.xml") );// Get the page number askedstring strPageAsked = Request.QueryString["page"];// If the page is not defined then set it to first oneif ( strPageAsked == null ){strPageAsked = "1";}int nGuestPerPage = 5;int nGuests = doc.ChildNodes[1].ChildNodes.Count;int nPageAsked = System.Convert.ToInt32(strPageAsked);int lowerbound = 1 + ( nPageAsked - 1 ) * nGuestPerPage;int upperbound = lowerbound + nGuestPerPage - 1;//Do XSLT transformationXslTransform xslt = new XslTransform();xslt.Load( Server.MapPath("guestbook.xslt") );//Build XLST Param listXsltArgumentList xsltArgs = new XsltArgumentList();xsltArgs.AddParam("lowerbound", "", lowerbound.ToString());xsltArgs.AddParam("upperbound", "", upperbound.ToString());//Transform XML to HTMLMemoryStream ms = new MemoryStream();xslt.Transform( doc, xsltArgs, ms );ms.Seek( 0, SeekOrigin.Begin );StreamReader sr = new StreamReader(ms);//Insert result in the View.aspx pageLiteralGuests.Text = sr.ReadToEnd();//Insert the pages navigator at the bottom of the pageint nPages = 0;if (( nGuests % nGuestPerPage) != 0 )nPages = 1 + (nGuests / nGuestPerPage);elsenPages = (nGuests / nGuestPerPage);LiteralGuests.Text += "Page(s) ";for (int n = 1; n <= nPages; n++){LiteralGuests.Text += ""LiteralGuests.Text += "";LiteralGuests.Text += n.ToString();LiteralGuests.Text += " ";}sr.Close();}
All transformation from XML to HTML is done in the guestbook.xslt file. This transformation requests two parameters: lowerbound and upperbound, representing the lower and upper indexed values according to the guestbook page to display. Basically, what we do is to loop from lower bound to upper bound and do the transformation:
= $lowerbound]">
This is, for example, the transformation used to display a guest with its email, if it is not defined as private:

You may look at the file guestbook.xslt for further details.
Conclusion
I would say that you gain to separate data from processes, and in this matter, XML helps a lot. If you would like to change the looks of the guestbook view, you need only to change the guestbook.xslt file.
Problems Faced