VB.Net – Web Programming ”; Previous Next A dynamic web application consists of either or both of the following two types of programs − Server-side scripting − these are programs executed on a web server, written using server-side scripting languages like ASP (Active Server Pages) or JSP (Java Server Pages). Client-side scripting − these are programs executed on the browser, written using scripting languages like JavaScript, VBScript, etc. ASP.Net is the .Net version of ASP, introduced by Microsoft, for creating dynamic web pages by using server-side scripts. ASP.Net applications are compiled codes written using the extensible and reusable components or objects present in .Net framework. These codes can use the entire hierarchy of classes in .Net framework. The ASP.Net application codes could be written in either of the following languages − Visual Basic .Net C# Jscript J# In this chapter, we will give a very brief introduction to writing ASP.Net applications using VB.Net. For detailed discussion, please consult the ASP.Net Tutorial. ASP.Net Built-in Objects ASP.Net has some built-in objects that run on a web server. These objects have methods, properties and collections that are used in application development. The following table lists the ASP.Net built-in objects with a brief description − Sr.No. Object & Description 1 Application Describes the methods, properties, and collections of the object that stores information related to the entire Web application, including variables and objects that exist for the lifetime of the application. You use this object to store and retrieve information to be shared among all users of an application. For example, you can use an Application object to create an e-commerce page. 2 Request Describes the methods, properties, and collections of the object that stores information related to the HTTP request. This includes forms, cookies, server variables, and certificate data. You use this object to access the information sent in a request from a browser to the server. For example, you can use a Request object to access information entered by a user in an HTML form. 3 Response Describes the methods, properties, and collections of the object that stores information related to the server”s response. This includes displaying content, manipulating headers, setting locales, and redirecting requests. You use this object to send information to the browser. For example, you use a Response object to send output from your scripts to a browser. 4 Server Describes the methods and properties of the object that provides methods for various server tasks. With these methods you can execute code, get error conditions, encode text strings, create objects for use by the Web page, and map physical paths. You use this object to access various utility functions on the server. For example, you may use the Server object to set a time out for a script. 5 Session Describes the methods, properties, and collections of the object that stores information related to the user”s session, including variables and objects that exist for the lifetime of the session. You use this object to store and retrieve information about particular user sessions. For example, you can use Session object to keep information about the user and his preference and keep track of pending operations. ASP.Net Programming Model ASP.Net provides two types of programming models − Web Forms − this enables you to create the user interface and the application logic that would be applied to various components of the user interface. WCF Services − this enables you to remote access some server-side functionalities. For this chapter, you need to use Visual Studio Web Developer, which is free. The IDE is almost same as you have already used for creating the Windows Applications. Web Forms Web forms consists of − User interface Application logic User interface consists of static HTML or XML elements and ASP.Net server controls. When you create a web application, HTML or XML elements and server controls are stored in a file with .aspx extension. This file is also called the page file. The application logic consists of code applied to the user interface elements in the page. You write this code in any of .Net language like, VB.Net, or C#. The following figure shows a Web Form in Design view − Example Let us create a new web site with a web form, which will show the current date and time, when a user clicks a button. Take the following steps − Select File → New → Web Site. The New Web Site Dialog Box appears. Select the ASP.Net Empty Web Site templates. Type a name for the web site and select a location for saving the files. You need to add a Default page to the site. Right click the web site name in the Solution Explorer and select Add New Item option from the context menu. The Add New Item dialog box is displayed − Select Web Form option and provide a name for the default page. We have kept it as Default.aspx. Click the Add button. The Default page is shown in Source view Set the title for the Default web page by adding a value to the <Title> tag of the page, in the Source view − To add controls on the web page, go to the design view. Add three labels, a text box and a button on the form. Double-click the button and add the following code to the Click event of the button − Protected Sub Button1_Click(sender As Object, e As EventArgs) _ Handles Button1.Click Label2.Visible = True Label2.Text = “Welcome to Tutorials Point: ” + TextBox1.Text Label3.Text = “You visited us at: ” + DateTime.Now.ToString() End Sub When the above code is executed and run using Start button available at the Microsoft Visual Studio tool bar, the following page opens in the browser − Enter your name and click on the Submit button − Web Services A web service is a web application, which is basically a class consisting of methods that could be used by other applications. It also follows a code-behind architecture