MELJUN CORTES Vb.net understanding web service.net

Visual Basic .NET Programming

What is a What is a What is a What is a Web Service?Web Service?Web Service?Web Service?

� allows access to components by means of

Internet and HTTP

� a class that is stored on one computer

that can be accessed on another computer

over the network

Understanding Web Service * Property of STIPage 1 of 14

� supporting frameworks for the Web

services:

� Open Internet Protocols

� XML Messages and SOAP

� Messages defined by Web Services

Description Language (WSDL)


Web Service Web Service Web Service Web Service ModuleModuleModuleModule

� used to group the files needed to create a

Web service

� contains two files:

� .asmx

• includes the WebService directive

.asmx.vb file


� .asmx.vb file

• contains the code that executes when a

Web Service method is invoked

<%@ WebService Language=”vb”

CodeBehind=”AdminUsr.asmx.vb”

Class=”WebApp.AdminUsr” %>


Adding Public Adding Public Adding Public Adding Public Subroutines or FunctionsSubroutines or FunctionsSubroutines or FunctionsSubroutines or Functions

� Example:

<WebMethod()> Public Function

AddAdminUsr(ByVal strName As

String) As String

‘ Functionality to add a user and

return new ID


return new ID

…

Return strNewId

End Function

<WebMethod()> Public Sub

DeleteAdminUsr(ByVal strId As

String)

‘ Functionality to delete a user based

on ID

…

End Sub


Dynamic Dynamic Dynamic Dynamic Discovery DocumentDiscovery DocumentDiscovery DocumentDiscovery Document

� contains information about the Web

service

� used to locate and discover Web services

� automatically created by ASP.NET


� automatically created by ASP.NET

� return the details of all Web Services

� uses the .vsdisco file extension

� used to exclude particular folders from

the dynamic discovery process


HTML Description Page HTML Description Page HTML Description Page HTML Description Page and WSDL Documentand WSDL Documentand WSDL Documentand WSDL Document

� The HTML description page

� describes Web services methods and

arguments

� displayed when Web service URL is entered

without specifying a particular method

name

� contains simple test utility methods

� provides test facilities for each methods of


� provides test facilities for each methods of

the Web service

� allows you to provide parameter through

an input field

� follows the format:

http://webservername:port/webservi

ce.asmx.

� Example:

http://localhost:3163/MyService.as

mx


HTML Description Page HTML Description Page HTML Description Page HTML Description Page and WSDL Documentand WSDL Documentand WSDL Documentand WSDL Document

� Web Services Description Language (WSDL)

� describes methods, arguments and

responses of a Web service

� created automatically by adding the ?WSDL

switch to the Web service URL

� Example:


� Example:

http://localhost:3163/MyService.as

mx?WSDL


Invoking a Web Service Invoking a Web Service Invoking a Web Service Invoking a Web Service from a Browser from a Browser from a Browser from a Browser

and a Clientand a Clientand a Clientand a Client

� To invoke a Web Service from a browser:

� enter the URL of the service, specify the

method name to run as well as parameter

values

� Syntax:

http://webservername/vdir/webservi


http://webservername/vdir/webservi

cename.asmx/MethodName?parameter

=value

� Examples:

http://www.myserver.com/User/Admin

Usr.asmx/AddAdminUsr?strName=Man

ny

<?xml version=”1.0” ?>

<string

xmlns=http://tempuri.org/>43-

124-21</string>




� HTTP GET method

� used to send the form data to the Web

server

� most commonly used for testing purposes

� SOAP protocol

� used for real application-to-application


� used for real application-to-application

communication

� difference between the HTTP-GET and

SOAP

� the way of sending data to the Web server




� To invoke a Web service from a client:

� add a Web reference to the Web Service

� enter the URL for the .asmx file

� select the required references

� create the client code for accessing a

component


� Example:

Private Sub btnSubmit_Click(ByVal

sender As System.Object, _

ByVal e As System.EventArgs)

Handles btnSubmit.Click

’Services is the given namespace

Dim usr As New Services.user( )

MessageBox.Show(usr.AddUser(txtNam

e.Text))

End Sub


Demo: Creating a Demo: Creating a Demo: Creating a Demo: Creating a Web ServiceWeb ServiceWeb ServiceWeb Service

� open Visual Studio 2005

� File > New Web Site

� select ASP.NET Web Service

� set Location to File System

� set Language to Visual Basic then click

OK

� delete the asmx file


� delete the asmx file

� delete the vb file

� right-click on the project name and click

Add New Item

� select Web Service in the Templates list

then set the Web service and click Add

� right-click on the App_Code and click

Add New Item

� select Class from the Installed Templates

list

� set the class name then click Add



� open the Code Editor for the .asmx file,

locate the Public Class definition then

modify the WebService attribute

<WebService(Namespace:=”http://tem

puri.org/”, _

Description:=” Web service demo

information.”


information.”

)> Public Class WebServiceDemo

� delete the code:

<WebMethod()> _

Public Function HelloWorld()

As String

Return "Hello World"

End Function



� To define the Web Service methods:

� add WebMethod attribute and Web service

method

<WebMethod(Description:="Retrieves

welcome message.")> _

Public Function GetMessage()

As String


As String

GetMessage = "Learning Web

services is fun!"

End Function

� To test the Web Service:

� right-click on the project name and select

Build Web Site

� right-click the .asmx file, and then click

View in Browser




� click the Service Description hyperlink



� click the Back button

� click the hyperlink of the method of the

Web Service


� click the Invoke button

Technology

MELJUN CORTES Vb.net understanding web service.net