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Sample Web Service: EG1

The first APLExample sample is supplied in samples\asp.net\webservices\eg1.asmx which is mapped via an IIS Virtual Directory to the URL: 

 http://localhost/dyalog.net.15.0.unicode.32/webservices/eg1.asmx

<%@ WebService Language="Dyalog" Class="APLExample" %>

:Class APLEXample: System.Web.Services.WebService
:Using System

 ∇ R←Add args
   :Access WebMethod
   :Signature Int32←Add Int32 arg1,Int32 arg2
   R←+/args
 ∇

:EndClass

The Add function defined above is exported as a method that takes exactly (and only) two parameters of type Int32 and returns a result of type Int32.

Line [3] could in fact be coded as: 

   R←args[1]+args[2]

because .NET guarantees that a client can only call the method by providing two 32-bit integers as parameters.

Testing APLExample from a Browser

If you connect to a URL that represents a Web Service, the browser displays a page that provides information about the service and the methods that it contains. In certain cases, but by no means all, the page also contains form fields that let you invoke a method from the browser.

The screen shot below shows the page displayed by Google Chrome when it is pointed at eg1.asmx. It shows that the Web Service is called APLExample, and that it exports a single method called Add. Furthermore, the Add method takes two parameters of type int, named arg1 and arg2.

eg1_1
Figure 1: eg1_1

The following screen shot shows the result of entering the values 23 and 19 into the form fields and then pressing the Invoke button.

In this case, the method returns an int value 42.

eg1_2
Figure 2: eg1_2

It is important to understand what is happening here.

Accessed in this way from a browser, a Web Service appears to be behaving like a Web Server; this is not the case.

It is simply that the browser detects that the target URL is a Web Service, and invokes an ASP+ page named DefaultSdlHelpGenerator.aspx that inspects the compiled class and returns an HTML view of the Web service.