Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Adding Logic to Your User Controls x 297
To add properties or methods to a user control, you add them to the Code Behind of the control.
The properties you add can take various forms. In its simplest form, a property looks exactly like
the properties you saw in Chapter 5. For more advanced scenarios you need to add View State properties
which are able to maintain their state across postbacks. In the next two exercises you see how
to create both types of properties.
Creating Your Own Data Types for Properties
To make the banner control more useful, you can add a second image to it that displays a horizontal
banner. You could also add a property to the control that determines whether to display the vertical
or horizontal image. You could do this by creating a numeric property of type System.Byte. Then
0 would be vertical and 1 would be horizontal, for example. However, this makes it hard to remember
what each number represents. You can make it a bit easier by creating a String property that
accepts the values Horizontal and Vertical. However, strings cannot be checked at compile time,
so you may end up with a spelling mistake, resulting in an error or in the incorrect banner being displayed.
The .NET Framework supplies a nice way to solve this by enabling you to create your own
data type in the form of an enumeration. With an enumeration, or enum for short, you assign numbers
to human-friendly text strings. Developers then use this readable text, while under the hood the
numeric value is used. The following snippet shows a basic example of an enum (notice how the VB
example doesn’t use commas, whereas they are required in C#):
VB.NET
Public Enum Direction
Horizontal
Vertical
End Enum
C#
public enum Direction
{
Horizontal,
Vertical
}
With these enums, the compiler assigns numeric values to the Horizontal and Vertical members
automatically, starting with 0 and counting upward. You can also define numeric values explicitly if
you want:
VB.NET
Public Enum Direction
Horizontal = 0
Vertical = 1
End Enum
C#
public enum Direction
{
Horizontal = 0,
Vertical = 1
}