When you add a WebClass designer to an IIS project (either as the first default
WebClass or as a WebClass that you add from the Project menu), VB automatically
puts some default code in the WebClass’ Start event procedure, as shown
in Listing 17.3.
LISTING 17.3
DEFAULT START EVENT PROCEDURE CODE IN A NEW WEBCLASS DESIGNER
Private Sub WebClass_Start()
‘Write a reply to the user
With Response
.Write "<html>"
.Write "<body>"
.Write "<h1><font face=""Arial"">WebClass1’s
Starting
Page</font></h1>"
.Write "<p>This response was created in the Start
event of WebClass1.</p>"
.Write "</body>"
.Write "</html>"
End With
End Sub
The WebClass’ Start event, as you might imagine, runs the first time
that an end user initiates a copy of your WebClass by navigating to the host ASP
page.
Note that the default code in the Start event calls the Write method of the
Response object. The Response object is in charge of sending information back
to the browser. The information to be sent will be HTML code that the browser
will then see as a Web page.
To examine the appearance of the unmodified default page sent back by the WebClass,
just run your project as soon as you have created it. The first time that you
run a WebClass project, you will see the Debugging tab of the Project Properties
dialog box as shown in Figure 17.2. Normally, you will leave the default options
as they are (that is, run the component using the default browser), and just click
the OK button.
After you have passed beyond the Save dialog box for the project’s files,
your browser (typically, Internet Explorer when you develop with Visual Studio)
will display the page created by the calls to Response.Write in the WebClass’
Start event procedure, as shown in Figure 17.3.
Note that the Browser’s Address box (indicating the URL of the current
page) points to an ASP file with the same name as your WebClass. VB automatically
generated the ASP file when you ran the project in the IDE. As mentioned previously,
the function of the ASP is to host the WebClass object that you are programming.
The ASP file will be distributed with your project when you use Package and Deployment
Wizard to create a setup package. You will not want to modify the ASP file, because
VB would only overwrite it the next time that you try to run your application
from the VB environment or distribute it with Package and Deployment Wizard.
If you choose the View, Source option from IE’s menu, you will see the
HTML code that your browser received, as shown in Listing 17.4.
LISTING 17.4
HTML SOURCE CODE SENT TO THE BROWSER BY THE DEFAULT START EVENT PROCEDURE’S
CODE IN WEBCLASS1
<html><body><h1><font face="Arial">WebClass1’s
Starting Page</font></h1><p>This response was created in the
Start event of WebClass1.</p></body></html>
You are seeing the HTML that the Start event procedure of the WebClass generated
with calls to Response.Write. Microsoft’s idea in providing you with the
default code in the Start event procedure is that you can modify the default calls
to Response.Write to suit your own purposes, as shown in Listing 17.5.
LISTING 17.5
CUSTOMIZED START EVENT PROCEDURE OF A WEBCLASS
Private Sub WebClass_Start()
‘Write a reply to the user
With Response
.Write "<html>"
.Write "<body>"
.Write "Page accessed at: " & Format(Now, "hh:mm")
.Write "<h1><font face=""Arial"">Order
Entry
system</font></h1>"
.Write "<p>Make your initial selection from the list.</p>"
.Write "</body>"
.Write "</html>"
End With
End Sub
Of course, such simple modifications as shown in Listing 17.5, no matter how
many lines of pure HTML code they might include, would not take full advantage
of an IIS application’s capabilities. You might as well just create an HTML
page or an ASP page with a text editor or Web authoring tool.
You can use VB’s more advanced processing and logic to create dynamic
HTML code (as illustrated in the line that includes the current time in Listing
17.5).
To take full advantage of the IIS application’s possibilities, however,
you will want to avail yourself of two more advanced IIS application features:
-
The capability to associate an HTML template with each WebClass object.
-
The capability to use WebItems to define and process custom events associated
with the HTML code for a WebClass. The following sections discuss these techniques.
The following sections discuss these techniques.
Programming With an HTML Template
