1. Open the myFirstWebService.asmx file in Code view.
   
    
2. Add code for a WebMethod called Subtract. The function has two input parameters and one output parameter containing the difference of the two input parameters. All parameters are of type Integer:

    

   <WebMethod> Public Function Subtract(a As Integer, b As Integer) As Integer 
       Return a - b
   End Function
   

3. Save and run the XML Web Service (hit the start button or press F5 to launch it).
   
    
4. A dynamically generated page describing your XML Web Service will automatically appear in a new instance of your Web browser.
   
    
5. You will see the XML Web service's HTML description file, containing two methods (Add and Subtract). 

   

6. Click the Subtract link at the top of the HTML description file.   This will bring up a details page about the Subtract web method -- including schema details about the SOAP payload used to invoke it, as well as an HTML form to invoke and test the method.

   

7. Enter 8 in the a parameter box.
   
    
8. Enter 3 in the b parameter box.
   
    
9. Click Invoke. 
   
    
10. The Web service will return an XML response that gives the difference of the two input parameters in a new instance of your Web browser.

    

11. Close the Web browser instance.

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