- Abstraction in Visual Basic.NET
- Encapsulation in VB.NET
- Polymorphism in VB.NET
- Inheritance in VB.NET
- Interface-Based Programming
- Summary
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Encapsulation in VB.NET
Encapsulation is the exposure of properties and methods of an object while hiding the actual implementation from the outside world. In other words, the object is treated as a black box—developers who use the object should have no need to understand how it actually works.
Encapsulation allows developers to build objects that can be changed without affecting the client code that uses them. The key is that the interface of the object, the set of exposed properties and methods of the object, doesn't change even if the internal implementation does. VB has supported encapsulation since version 4.0.
Lets take a look at two trivial examples of a Person class. Listings 3.5 and 3.6 and implement the same functionality in two different ways.
Listing 3.5 Person Class Implementation #1
Public Class Person
Private m_sFirstName as String
Private m_sLastName as String
Public Property FirstName() as String
Get
FirstName = m_sFirstName
End Get
Set(ByVal Value as String)
m_sFirstName = Value
End Set
End Property
Public Property LastName() as String
Get
LastName = m_sLastName
End Get
Set(ByVal Value as String)
m_sLastName = Value
End Set
End Property
ReadOnly Property FullName() as String
Get
FullName = m_sLastName & ", " & m_sFirstName
End Get
End Property
End Class
Listing 3.6 Person Class Implementation #2
Public Class Person
Private m_sFirstName as String
Private m_sLastName as String
Private m_sFullName as String
Public Property FirstName() as String
Get
FirstName = m_sFirstName
End Get
Set(ByVal Value as String)
m_sFirstName = Value
m_sFullName = m_sLastName & ", " & m_sFirstName
End Set
End Property
Public Property LastName() as String
Get
LastName = m_sLastName
End Get
Set(ByVal Value as String)
m_sLastName = Value
m_sFullName = m_sLastName & ", " & m_sFirstName
End Set
End Property
ReadOnly Property FullName() as String
Get
FullName = m_sFirstName
End Get
End Property
End Class
This illustrates how the internal implementation of the classes is different but the external interface encapsulates how the class works internally. That is the goal of encapsulation: to allow a developer to transparently use different implementations of the same object.