N342 ActiveX

Microsoft has developed the ActiveX technology in part to provide Web designers with some programming ability to extend VBScript, JavaScript, PerlScript, etc. These can be used on either the client or server side, though use on the client side (the browser) requires:

the browser supports ActiveX, IE does, Netscape does not (though there have been numerous announcements to the contrary over the years).
the ActiveX component must be downloaded and registered on the client machine. Since ActiveX components have complete access to the client machine this presents a serious security issue. This limits the client-side use to intranets where the component can generally be trusted since most sane users would reject downloading a potential virus or merely flawed program to their machine over the Internet.

The server-side use is more positive since a designer can implement their own components, place them on their server, and use them to generate standard HTML for a client. The client would not need to know that an ActiveX component was involved in generating the HTML. Motivations for using ActiveX are driven primarily by a desire (need) to use weak scripting languages like VBScript or JavaScript in ASP that require considerable help to do anything useful in general. Examples of ActiveX use would be to write a TCP protocol handler in Visual Basic to provide a server-side scripting language component for communicating with another server.

The following simple example is intended to provide the nuts and bolts of implementing an ActiveX component in Visual Basic and using the component in a VBScript (or JavaScript or PerlScript would work the same) on a server.

**ActiveX Class Definitions in Visual Basic**
Visual Basic - HelloWorldClass Option Explicit 'Global scripting context Dim ASPsc As ScriptingContext 'Automatically called when object is instantiated Public Sub OnStartPage(ASP_Scripting_Context As ScriptingContext) 'Set global variable to reference 'scripting context in other subs Set ASPsc = ASP_Scripting_Context End Sub Public Sub Greeting(myName As String) Dim ASPResponse ' Create Response object from ' global scripting context object. Set ASPResponse = ASPsc.Response ASPResponse.Write "<textarea>" ASPResponse.Write "Hello World " + myName ASPResponse.Write "</textarea>" End Sub	HelloWorld.Asp <H1>VB HelloWorldClass</H1> <% ' Create our HelloWorldClass object Set HW = Server.CreateObject("HelloWorldProject.HelloWorldClass") ' Call Greetings subroutine HW.Greeting("Ray") %> Output

Exercise 1 - Creating the HelloWorldClass in Visual Basic

VB.
1. New VB ActiveX DLL project.
2. Open menu and check: Project | References | Microsoft Active Server Pages Object Library
3. Enter VB HelloWorldClass program
4. Save as class: HelloWorldClass.cls and project HelloWorldProject. In the ASP script the object is referred as:
  Set HW = Server.CreateObject("HelloWorldProject.HelloWorldClass")
  
  would be class HelloWorldClass and the project HelloWorldProject.
5. File | Make - Save DLL as HelloWorldDLL.dll
ASP: Copy the ASP script and save as HelloWorld.Asp.
Browser: Enter the URL for HelloWorld.Asp