IT SOLUTIONS
Your full service technology partner! 
-Collapse +Expand
To/From Code
-Collapse +Expand Cross Ref Guide
-Collapse +Expand Members-Only
Sign in to see member-only pages.
   ► KBTo/From GuidesAccess VBAData Structures    Print This   

Cross Ref > Data Structures

By Mike Prestwood

Access VBA versus C#: A side by side comparison between Access VBA and C#.

 
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.

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:  
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
[Not specified yet. Coming...]




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.

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"))
C#:   Dictionary
Syntax Example:
//using System.Collections.Generic;
 
Dictionary <String, String> airports = new Dictionary <String, String>();
airports.Add("LAX", "Los Angeles"); 
airports.Add("SFO", "San Francisco");
airports.Add("SAN", "San Diego");
MessageBox.Show(airports["LAX"]);




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).

Access VBA:   Not Supported

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

C#: 

Although pointer data types in C# coding are less important than in other languages such as C++, C# does support developer defined pointers. Use the * operator to declare a pointer data type. Use the & operator to return the current address of a variable.

In .Net managed coding the use of pointers is not safe because the garbage collector may move memory around. To safely use pointers, use the unsafe keyword. However, avoid unsafe code if possible.

C++/CLI has more extensive support for pointers than C#. If you have needs that go beyond what C# offers, you can code in C++/CLI and add it to your project.

Syntax Example:
//Declare a pointer of type integer.
Integer *PCounter;




-
  Load Time=less than 1 second.
 
Print This
-
 
Have a question? Need our services? Contact us now.
--Mike Prestwood

Call: 916-726-5675

email: info@prestwood.com


-
 
Connect With Us...
PrestwoodBoards
Join Us!
Facebook
Like our page!!!
Twitter
Follow us!
LinkedIn
Join Group
YouTube
View channel.
Go ahead!   Use Us! Call: 916-726-5675 


©1995-2014 Prestwood IT Solutions.   [Security & Privacy]   Made in the U.S.A..   No H1-B.   No offshoring.