Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Object Orientation Basics x 191
Properties
Properties of an object are the characteristics the object has. Consider a Person object. What kind
of properties does a Person have? It’s easy to come up with many different characteristics, but the
most common are:
‰ First name
‰ Last name
‰ Date of birth
You define a property in a class with the Property keyword (in VB.NET) or with a property header
similar to a method in C#. In both languages, you use a Get block (get in C#) and a Set block
(set in C#) to define the so-called getters and setters of the property. The getter is accessed when
an object is asked for the value of a specific property, and the setter is used to assign a value to the
property. Properties only provide access to underlying data stored in the object; they don’t contain
the actual data. To store the data, you need what is called a backing variable. This is often a simple
field defined in the class that is able to store the value for the external property. In the following
example, the variable _firstName is the backing variable for the FirstName property:
VB.NET
Public Class Person
Private _firstName As String
Public Property FirstName() As String
Get
Return _firstName
End Get
Set(value As String)
_firstName = value
End Set
End Property
End Class
C#
public class Person
{
private string _firstName;
public string FirstName
{
get { return _firstName; }
set { _firstName = value; }
}
}
It is common to prefix the private backing variables with an underscore, followed by the first word in
all lowercase, optionally followed by more words that start with a capital again. So the FirstName
property has a backing variable called _firstName, LastName has one called _lastName, and so on.
This way, all variables that apply to the entire class are nicely packed together in the IntelliSense list.
Simply type an underscore in your code and you’ll get the full list of private variables. Note that the
underscore is typically not used when defining variables inside a function or a subroutine.