Microsoft Visual Basic 2010 Step by Step eBook

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Chapter 12

Working with Collections

After completing this chapter, you will be able to:

n Manipulate the Controls collection on a form.

n Use a For Each... Next loop to cycle through objects in a collection.

n Create your own collections for managing Web site URLs and other information.

n Use VBA collections within Microsoft Office.

In this chapter, you’ll learn how to use groups of objects called collections in a Microsoft

Visual Basic program. You’ll learn how to manage information with collections and process

collection objects by using For Each... Next loops. When you combine collection- processing

skills with what you learned about arrays in Chapter 11, “Using Arrays to Manage Numeric

and String Data,” you’ll have much of what you need to know about managing data

effectively in a program, and you’ll have taken your first steps in manipulating the object

collections exposed by Microsoft Visual Studio 2010 and popular Windows applications.

Working with Object Collections

In this section, you’ll learn about collections, a powerful mechanism for controlling objects

and other data in a Visual Basic program. The Microsoft .NET Framework maintains several

standard object collections that you can use when you write your programs. You can use

Visual Studio to browse your system for collections and other application objects.

You already know that objects on a form are stored together in the same file. But did you

also know that Visual Basic considers the objects to be members of the same group? In Visual

Studio terminology, the entire set of objects on a form is called the Controls collection. The

Controls collection is created automatically when you open a new form, and when you add

objects to the form, they become part of that collection.

Each collection in a program has its own name so that you can reference it as a distinct unit

in the program code. For example, you use the Controls name to reference the collection of

objects on a form. This grouping method is similar to the way arrays group a list of elements

together under one name, and like Visual Basic arrays, the Controls collection is zero-based.

If you have more than one form in a project, you can create public variables associated with

the form names and use those variables to differentiate one Controls collection from another.

(You’ll learn more about using public variables to store form data in Chapter 14, “Managing

Windows Forms and Controls at Run Time .”) You can even add controls programmatically to

the Controls collection in a form.

Table of Contents

Working with Collections.................................. 297

Working with Object Collections...................................... 297

Referencing Objects in a Collection.............................. 298

Writing For Each... Next Loops................................. 298

Experimenting with Objects in the Controls Collection............. 299

Using the Name Property in a For Each... Next Loop.............. 302

Creating Your Own Collections....................................... 304

Declaring New Collections...................................... 304

One Step Further: VBA Collections.................................... 309

Entering the Word Macro....................................... 310

Chapter 12 Quick Reference.......................................... 311