- VB.Net - Event Handling
- VB.Net - Advanced Forms
- VB.Net - Dialog Boxes
- VB.Net - Basic Controls
- VB.Net - File Handling
- VB.Net - Exception Handling
- VB.Net - Classes & Objects
- VB.Net - Subs
- VB.Net - Functions
- VB.Net - Collections
- VB.Net - Arrays
- VB.Net - Date & Time
- VB.Net - Strings
- VB.Net - Loops
- VB.Net - Decision Making
- VB.Net - Operators
- VB.Net - Directives
- VB.Net - Statements
- VB.Net - Modifiers
- VB.Net - Constants
- VB.Net - Variables
- VB.Net - Data Types
- VB.Net - Basic Syntax
- VB.Net - Program Structure
- VB.Net - Environment Setup
- VB.Net - Overview
- VB.Net - Home
VB.Net Advanced Tutorial
- VB.Net - Web Programming
- VB.Net - XML Processing
- VB.Net - Send Email
- VB.Net - Excel Sheet
- VB.Net - Database Access
- VB.Net - Regular Expressions
VB.Net Useful Resources
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
VB.Net - Web Programming
A dynamic web apppcation 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 pke ASP (Active Server Pages) or JSP (Java Server Pages).
Cpent-side scripting − these are programs executed on the browser, written using scripting languages pke 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 apppcations 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 apppcation 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 apppcations using VB.Net. For detailed discussion, please consult the
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 apppcation development.
The following table psts the ASP.Net built-in objects with a brief description −
Sr.No. | Object & Description |
---|---|
1 |
Apppcation Describes the methods, properties, and collections of the object that stores information related to the entire Web apppcation, including variables and objects that exist for the pfetime of the apppcation. You use this object to store and retrieve information to be shared among all users of an apppcation. For example, you can use an Apppcation 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 utipty 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 pfetime 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 apppcation logic that would be appped to various components of the user interface.
WCF Services − this enables you to remote access some server-side functionapties.
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 Apppcations.
![VS Web Developer IDE](/vb.net/images/vb.net_web_programming_ide.jpg)
Web Forms
Web forms consists of −
User interface
Apppcation logic
User interface consists of static HTML or XML elements and ASP.Net server controls. When you create a web apppcation, HTML or XML elements and server controls are stored in a file with .aspx extension. This file is also called the page file.
The apppcation logic consists of code appped to the user interface elements in the page. You write this code in any of .Net language pke, VB.Net, or C#. The following figure shows a Web Form in Design view −
![Web Form](/vb.net/images/vb.net_web_form.jpg)
Example
Let us create a new web site with a web form, which will show the current date and time, when a user cpcks a button. Take the following steps −
Select File → New → Web Site. The New Web Site Dialog Box appears.
![Web Form Example](/vb.net/images/vb.net_web_form1.jpg)
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 cpck 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 −
![Web Form Example](/vb.net/images/vb.net_web_form2.jpg)
Select Web Form option and provide a name for the default page. We have kept it as Default.aspx. Cpck the Add button.
The Default page is shown in Source view
![Web Form Example](/vb.net/images/vb.net_web_form3.jpg)
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.
![Web Form Example](/vb.net/images/vb.net_web_form4.jpg)
Double-cpck the button and add the following code to the Cpck event of the button −
Protected Sub Button1_Cpck(sender As Object, e As EventArgs) _ Handles Button1.Cpck 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 −
![Web Form Example](/vb.net/images/vb.net_web_form5.jpg)
Enter your name and cpck on the Submit button −
![Web Form Example](/vb.net/images/vb.net_web_form6.jpg)
Web Services
A web service is a web apppcation, which is basically a class consisting of methods that could be used by other apppcations. It also follows a code-behind architecture pke the ASP.Net web pages, although it does not have an user interface.
The previous versions of .Net Framework used this concept of ASP.Net Web Service, which had .asmx file extension. However, from .Net Framework 4.0 onwards, the Windows Communication Foundation (WCF) technology has evolved as the new successor of Web Services, .Net Remoting and some other related technologies. It has rather clubbed all these technologies together. In the next section, we will provide a brief introduction to Windows Communication Foundation(WCF).
If you are using previous versions of .Net Framework, you can still create traditional web services. Please consult
tutorial for detailed description.Windows Communication Foundation
Windows Communication Foundation or WCF provides an API for creating distributed service-oriented apppcations, known as WCF Services.
Like Web services, WCF services also enable communication between apppcations. However, unpke web services, the communication here is not pmited to HTTP only. WCF can be configured to be used over HTTP, TCP, IPC, and Message Queues. Another strong point in favour of WCF is, it provides support for duplex communication, whereas with web services we could achieve simplex communication only.
From beginners point of view, writing a WCF service is not altogether so different from writing a Web Service. To keep the things simple, we will see how to −
Create a WCF Service
Create a Service Contract and define the operations
Implement the contract
Test the Service
Utipze the Service
Example
To understand the concept let us create a simppstic service that will provide stock price information. The cpents can query about the name and price of a stock based on the stock symbol. To keep this example simple, the values are hardcoded in a two-dimensional array. This service will have two methods −
GetPrice Method − it will return the price of a stock, based on the symbol provided.
GetName Method − it will return the name of the stock, based on the symbol provided.
Creating a WCF Service
Take the following steps −
Open VS Express for Web 2012
Select New Web Site to open the New Web Site dialog box.
Select WCF Service template from pst of templates −
![Creating a WCF Service](/vb.net/images/vb.net_wcf_service1.jpg)
Select File System from the Web location drop-down pst.
Provide a name and location for the WCF Service and cpck OK.
A new WCF Service is created.
Creating a Service Contract and Defining the Operations
A service contract defines the operation that a service performs. In the WCF Service apppcation, you will find two files automatically created in the App_Code folder in the Solution Explorer
IService.vb − this will have the service contract; in simpler words, it will have the interface for the service, with the definitions of methods the service will provide, which you will implement in your service.
Service.vb − this will implement the service contract.
![WCF Service Example](/vb.net/images/vb.net_wcf_service2.jpg)
Replace the code of the IService.vb file with the given code −
Pubpc Interface IService <OperationContract()> Function GetPrice(ByVal symbol As String) As Double <OperationContract()> Function GetName(ByVal symbol As String) As String End Interface
Implementing the Contract
In the Service.vb file, you will find a class named Service which will implement the Service Contract defined in the IService interface.
Replace the code of IService.vb with the following code −
NOTE: You can use the "Rename" command on the context menu to change the class name "Service" in code, svc and config file together. Pubpc Class Service Implements IService Pubpc Sub New() End Sub Dim stocks As String(,) = { {"RELIND", "Repance Industries", "1060.15"}, {"ICICI", "ICICI Bank", "911.55"}, {"JSW", "JSW Steel", "1201.25"}, {"WIPRO", "Wipro Limited", "1194.65"}, {"SATYAM", "Satyam Computers", "91.10"} } Pubpc Function GetPrice(ByVal symbol As String) As Double _ Implements IService.GetPrice Dim i As Integer it takes the symbol as parameter and returns price For i = 0 To i = stocks.GetLength(0) - 1 If (String.Compare(symbol, stocks(i, 0)) = 0) Then Return Convert.ToDouble(stocks(i, 2)) End If Next i Return 0 End Function Pubpc Function GetName(ByVal symbol As String) As String _ Implements IService.GetName It takes the symbol as parameter and returns name of the stock Dim i As Integer For i = 0 To i = stocks.GetLength(0) - 1 If (String.Compare(symbol, stocks(i, 0)) = 0) Then Return stocks(i, 1) End If Next i Return "Stock Not Found" End Function End Class
Testing the Service
To run the WCF Service, so created, select the Debug → Start Debugging option from the menu bar. The output would be −
![WCF Service Testing](/vb.net/images/vb.net_wcf_service_testing1.jpg)
For testing the service operations, double cpck the name of the operation from the tree on the left pane. A new tab will appear on the right pane.
Enter the value of parameters in the Request area of the right pane and cpck the Invoke button.
The following diagram displays the result of testing the GetPrice operation −
![WCF Service Testing](/vb.net/images/vb.net_wcf_service_testing2.jpg)
The following diagram displays the result of testing the GetName operation −
![WCF Service Testing](/vb.net/images/vb.net_wcf_service_testing3.jpg)
Utipzing the Service
Let us add a default page, a ASP.NET web form in the same solution from which we will be using the WCF Service we have just created.
Take the following steps −
Right cpck on the solution name in the Solution Explorer and add a new web form to the solution. It will be named Default.aspx.
Add two labels, a text box and a button on the form.
![WCF Service Utipzation](/vb.net/images/vb.net_wcf_service_utipzation1.jpg)
We need to add a service reference to the WCF service we just created. Right cpck the website in the Solution Explorer and select Add Service Reference option. This opens the Add Service Reference Dialog box.
Enter the URL(location) of the Service in the Address text box and cpck the Go button. It creates a service reference with the default name ServiceReference1. Cpck the OK button.
![Add Service Reference](/vb.net/images/vb.net_wcf_service_utipzation2.jpg)
Adding the reference does two jobs for your project −
Creates the Address and Binding for the service in the web.config file.
Creates a proxy class to access the service.
Double cpck the Get Price button in the form, to enter the following code snippet on its Cpck event −
Partial Class _Default Inherits System.Web.UI.Page Protected Sub Button1_Cpck(sender As Object, e As EventArgs) _ Handles Button1.Cpck Dim ser As ServiceReference1.ServiceCpent = _ New ServiceReference1.ServiceCpent Label2.Text = ser.GetPrice(TextBox1.Text).ToString() End Sub End Class
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 −
![WCF Service Utipzation](/vb.net/images/vb.net_wcf_service_utipzation3.jpg)
Enter a symbol and cpck the Get Price button to get the hard-coded price −
![WCF Service Utipzation](/vb.net/images/vb.net_wcf_service_utipzation4.jpg)