To/From Code

	Languages
BROWSEBYLANGUAGE Access VBA ASP Classic C# C++ C++/CLI Corel Paradox Delphi Delphi Prism Java JavaScript Perl PHP VB Classic VB.Net

	Categories
BROWSEBYCATEGORY +Tool Basics +Language Basics +Language Details -Data Structures ◄╣ Array Associative Array Pointers +Statements +Operators +Commands +Database +OOP Basics +OOP Details

	VB.Net Guides
VB.Net To/From Conversion Guides VB.Net and ASP Classic VB.Net and C# VB.Net and C++ VB.Net and C++/CLI VB.Net and Corel Paradox VB.Net and Delphi VB.Net and Delphi Prism VB.Net and Java VB.Net and JavaScript VB.Net and Perl VB.Net and PHP VB.Net and VB Classic

Cross Ref Guide

VB.NETLANGUAGE

VB.Net

VB.NETANDACCESS VBATOC

Overview

+Tool Basics

Report Tools Overview

+Language Basics

+Language Details

-Data Structures◄╣

Array

+Statements

+Operators

+Commands

+OOP Basics

+OOP Details

	Members-Only
Sign in to see member-only pages.

► KB ► To/From Guides ► VB.Net ► Data Structures

Print This

Cross Ref > Data Structures

By Mike Prestwood

VB.Net versus Access VBA: A side by side comparison between VB.Net and Access VBA.

Data Structures

Data structures allow you to store and work with data. Common data structures include arrays, associative arrays, etc.

Array

[Other Languages]

Languages Focus

A data structure in which individual values (called elements or items) may be located by reference to one or more integer index variables, the number of such indices being the number of dimensions in the array.

Arrays can start with an index value of 0 or 1, sometimes referred to as 0 based or 1 based.

[Not specified yet. Coming...]

Access VBA: x = Array()

Arrays in Access VBA use a 0-based indice. Use UBound to get the number of elements. UBound returns -1 if the array has no elements, 0 if it has 1, 1 if it has 2, etc.

Syntax Example: 1 certification question.

Dim MyArray As Variant
Dim i As Integer
 
MyArray = Array("Mike", "Lisa", "Felicia", "Nathan")
 
If UBound(MyArray) > -1 Then
  For i = 0 To UBound(MyArray)
    MsgBox (MyArray(i))
  Next
End If

Associative Array

[Other Languages]

A set of unique keys linked to a set of values. Each unique key is associated with a value. Think of it as a two column table. MyArray['CA'] = 'California' MyArray['AR'] = 'Arizona'

Languages Focus

Associative arrays are also known as a dictionary or a hash table in other languages.

VB.Net: Dictionary

An associative array links a set of keys to a set of values. In Visual Basic, associative arrays are implemented as Dictionaries.

This code produces a message box saying "Nevada."

Syntax Example: 1 certification question.

//Imports System.Collections.Generic
�

Dim States As New Dictionary(Of String, String)


States.Add("CA", "California")
States.Add("NV", "Nevada")

MsgBox(States("NV"))

Associative Arrays in Visual Basic (a Dictionary)

Access VBA: Collection

In addition to Add and Item, collections also offer Count and Remove. Notice that Add uses the format of Value, Key (which is backwards from many other languages).

Syntax Example:

Dim States As New Collection
   
States.Add "California", "CA"
States.Add "Nevada", "NV"
     
MsgBox (States.Item("CA"))

Access VBA Associative Array (Collection)

Pointers

[Other Languages]

General Info: Pointers / References

A pointer is a variable type that allows you to refer indirectly to another object. Instead of holding data, a pointer holds the address to data -- the address of another variable or object. You can change the address value a pointer points to thus changing the variable or object the pointer is pointing to.

A reference is a type of pointer that cannot change and it must always point to a valid storage (no nulls).

VB.Net: None

VB.Net doesn't support pointers. The closest it comes is IntPtr which you use to get pointer handles on windows, files, etc.

C# does have better support for pointers and C++/CLI has extensive support. One solution when it's really needed in VB.Net is to code in C# or C++/CLI and add it to your project.

However, VB.Net does support references.

More Info / Comment 1 certification question.

Access VBA: Not Supported

Same as VB Classic. Access VBA does not offer developer defined pointers.