Asp Classic Vbscript

How to Traverse a Collection in Classic ASP

When working with Classic ASP, one common task is to traverse collections of objects. A frequent programmatic approach could involve iteration through a set of items using the familiar For Each construct. However, if you’re accustomed to environments like VB.NET or modern frameworks, you may find this process in Classic ASP a bit different. In this post, we’ll explore how you can successfully traverse a collection in Classic ASP and address some of the challenges related to it.

The Problem with Traversing Collections in Classic ASP

In Classic ASP, using For Each is a straightforward concept, but implementing this concept requires preparation, especially if you’re coming from a modern programming background. Specifically, the types of collections you can iterate over should be correctly set up outside the VBScript environment due to Classic ASP’s limitations. For many, this can lead to confusion, particularly if you’re trying to apply modern logic to a legacy system.

A Simple Example of What You Want to Accomplish

You might wish to achieve the following syntax in your Classic ASP application:

For Each thing In things
    ' Process thing
Next

The challenge arises because the elements within things must be set up properly before this syntax can be applied.

Solution: Setting Up Your Collection

To traverse a collection in Classic ASP, you will need to utilize custom collections effectively. Here’s how you can do it:

Step 1: Create a Custom Collection

In Classic ASP, you cannot directly use VBScript to create collections that can be traversed. Instead, you must define a custom collection in VB6. Here’s a basic outline of how to set that up:

  1. Define a Custom Collection Class: Write your collection class in VB6 which allows you to manage your objects. You may refer to the VB Helper guide for detailed instructions.
  2. Compile to ActiveX DLL: After crafting your collection class, compile it into an ActiveX DLL. This step may involve numerous configurations specific to your environment, so be sure to follow VB6 guidelines closely.
  3. Register the DLL on Your Web Server: This allows ASP to access the collection you just created. Use the regsvr32 command to register your DLL on the server.

Step 2: Accessing Your Collection in ASP

Once your collection is created and registered, you can access it in your ASP script like this:

<%
Set myCollection = Server.CreateObject("Your.Collection.ClassName")
' Populate your collection
For Each thing In myCollection
    Response.Write(thing.PropertyName) ' Output item property
Next
%>

Key Points to Remember

  • Custom Collections: Always define and register your custom collection outside of VBScript.
  • Collection Access: Use the ActiveX DLL through Server.CreateObject to access your collection in ASP code.
  • Processing Individual Items: Utilize properties or methods accessible via each item in your collection during traversal.

Conclusion

Traversing a collection in Classic ASP might not be as seamless as in younger frameworks, but with a few steps involving creating and registering a custom collection, you can achieve effective iteration using For Each. Understanding how to properly set up your environment and the tools you have at your disposal can make all the difference in successful collection management.

If you’re still feeling overwhelmed, don’t hesitate to consult the resource links or community forums dedicated to Classic ASP for further clarification and support. Happy coding!