XML Web Services 

Sample Service 2

In this section we will create a Calculator Web service that works similar to a Calculator and performs operations like Add, Subtract, Multiply, Divide and we will consume this Web service with a Visual Basic Windows Application. To start, open a new project and select ASP .NET Web service or add a new Web service to the existing ASP .NET Web service project by right-clicking the project name in Solution Explorer and selecting Add->Add Web service. Name this project as Calculator, open the code behind file and start writing the following code.

Imports System Imports System.Web.Services <WebService(Namespace := "http://tempuri.org/")> _ Public Class Service1 Inherits System.Web.Services.WebService #Region " Web Services Designer Generated Code " #End Region <WebMethod(Description:="Click to Add numbers")> Public Function Add_ (ByVal x As Integer, ByVal y As Integer) As Integer 'this method adds two numbers by accepting the input from the user 'Description property allows to document the functionality of the Web method. Return x + y End Function <WebMethod(Description:="Click to Subtract numbers")> Public Function Subtract_ (ByVal x As Integer,ByVal y As Integer) As Integer 'this method subtracts by accepting the input from the user Return x - y End Function <WebMethod(Description:="Click to Multiply numbers")> Public Function Multiply_ (ByVal x As Integer,ByVal y As Integer) As Integer 'this method multiplies two numbers by accepting the input from the user Return x * y End Function <WebMethod(Description:="Click to Divide numbers")> Public Function Divide_ (ByVal x As Integer,ByVal y As Integer) As Integer 'this method divides two numbers by accepting the input from the user If (y = 0) Then Throw New Exception("Can't divide by zero") 'if number entered is 0 throws an exception End If Return x / y End Function End Class

Once when you finish with the code run the service by selecting Debug->Start from the main menu or by pressing F5 on the keyboard. The Service that loads can be viewed by clicking here. You can view all the methods we created in code along with the method description on that page. Also you can enter some values in the Textboxes and test the service. We will consume this service in a Windows Form.

Consuming this Web service

Open a new Visual Basic Project and select Windows Application from the template. From the toolbox add a Button to the form. Our intention here is to consume the Web service which we created with this Windows Application. When we click the Button it will call the method which we specify in it's click event and will return the calculated result in a MessageBox.

Adding Web Service Reference to the Windows Application

We can add a reference to the Web service in two ways, with Solution Explorer and using WSDL tool. In the Solution Explorer right click on references and select Add Web Reference. That opens up a template similar to the image below.

In the address bar type the URL of the Calculator service which we created. Since it's in the root directory of IIS you need to type the following address: http://localhost/Calculator/Service1.asmx.  It should look like the image below.

After the Calculator service is loaded, click Add Reference. That adds a reference to the Calculator service.

To use WSDL tool to add a reference to this Web service, open Visual Studio .NET command prompt, change the folder in the command prompt to the location where you created Calculator and type the following:
WSDL "http://localhost/Calculator/Service1.asmx" /l:VB. After you finish typing the command, in Solution Explorer, right-click Calculator, select Add and then click Add Existing Item. Locate Service1.vb, and then click to select it. Click Open.

Calling the Service from Windows Form

Open Form1 and place the following code. Recall that we are calling a method when the Button in this application is clicked. We need to create an instance of the proxy class localhost.Service1 and call the function, passing a string argument. The code for that looks like this:

Public Class Form1 Inherits System.Windows.Forms.Form #Region " Windows Form Designer generated code " #End Region Dim myService As localhost.Service1 = New localhost.Service1() 'creating an instance  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As_ System.EventArgs) Handles MyBase.Load End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As_ System.EventArgs) Handles Button1.Click MessageBox.Show("Sum is " & myService.Add(10, 20)) 'calling the Add method in the Web Service returning the result in a messagebox End Sub End Class

Once you finish with the application, run the form and click on the Button. The sum of two numbers will be displayed in a MessageBox. We not only created a Web service but also consumed the service in other application.