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Posted 19 Oct 2004


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Using Structures in VB.NET

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19 Oct 20042 min read
Through this article, I wanted to introduce you to the structures in VB.NET. Also, I compared and contrasted Structures to Classes.


Structures are complex data types that encapsulate small pieces of tightly related data items. As with Classes, Structures can contain data members as well as member methods to work with data inside a structure. Since the in-memory representation of Structure is 'value type', memory management is handled efficiently.

Structures Vs Classes

Value typeReference type
Supports data members, code members (methods) and eventsSupports data members, code members (methods) and events
Can not inheritSupports inheritance
Preferable when you perform large number of operations on each instancePreferable when you need to initialize one or more members upon creation
Can not control initialization using structure variableCan have parameterized constructors
Less flexible, limited event handling supportMore flexible, unlimited event handling support


Structures are declared using Structure ... End Structure statements. Between these two statements, there must be at least one member declared. This member can be of any data type, non-shared and non-event. The following example shows how to encapsulate product info into a structure called Product.

Private Structure Product
    'Declare data members
    Public ProductID as Integer
    Public ProductName as String
    Private UnitPrice as Single

    'Declare code members
    Public Function GetPrice() as Single
        GetPrice = UnitPrice
    End Function
End Structure

In the above example, the Product structure is declared as Private. That means you can not access it from the object of the class where you defined it. As you can see, the data member UnitPrice is declared as Private, yes, you are right, you can't access it outside the structure.

Note that there is a function GetPrice defined within the Structure. Using this code member, one can get UnitPrice of a product. You can also define Sub procedures, properties and events. You can define a property as a default property, but it must accept at least one argument. You can declare events using Shared Sub procedure. To cause an event to actually happen, you have to use RaiseEvent statement.

The default accessibility for a structure is Public. You can use Private, Protected and Friend keywords also. You must specify accessibility for every member you declare inside a Structure. If you declare them with Dim statement, they are considered as Public. Remember that you can not initialize a Structure's data members at the time of instantiation. You have to access and initialize them individually after creation of a Structure variable or through a Structure code member. If you assign one Structure variable to another, a new copy is created in the other variable. Hence the changes to the values of first variable does not happen to the second. On the other hand, if you assign a Class object to another, changes to the data of one object reflects in the other. This is obvious in the case of Classes because the two objects in the above situation share the same instance.


  • Use Structures only if you want to use tiny pieces of related data as a single composite data type that resembles a built-in data type.
  • Use Classes if you can't decide which one to use among Classes and Structures. Because, Classes are more flexible. Though there are storage and performance advantages with Structures, often they are negligible.


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About the Author

India India
I have been using .NET ever since its inception, mostly to develop Web applications. Currently working in Hyderabad, India as .NET Consultant for a global software company. Outside work, I love to create small applications to gain in-depth understanding of a technology. Also, I try to help out fellow developers within my community.

Comments and Discussions

NewsAnother Difference Pin
dodiggitydag27-Jul-06 3:42
Memberdodiggitydag27-Jul-06 3:42 
QuestionStructures-How are they used? Pin
valtech_answer15-Nov-04 9:47
Membervaltech_answer15-Nov-04 9:47 
AnswerRe: Structures-How are they used? Pin
Anonymous29-Jul-05 0:14
MemberAnonymous29-Jul-05 0:14 
GeneralConstuctors Pin
Steven Campbell20-Oct-04 7:46
MemberSteven Campbell20-Oct-04 7:46 
GeneralRe: Constuctors Pin
Tony Phillips21-Jun-05 9:52
MemberTony Phillips21-Jun-05 9:52 
GeneralRe: Constuctors Pin
Steven Campbell22-Jun-05 2:12
MemberSteven Campbell22-Jun-05 2:12 
Tony Phillips wrote:
That is not a constructor

Ah, a well reasoned argument, presented in a thoroughly convincing manner. The final word[^].

my blog
GeneralRe: Constuctors Pin
Hypnotron6-Nov-05 17:43
MemberHypnotron6-Nov-05 17:43 
GeneralRe: Constuctors Pin
Luca Crisi, MCP5-Jun-08 2:05
MemberLuca Crisi, MCP5-Jun-08 2:05 

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