C# 4 and .NET 4

Classes ❘ 77
This code shows how the color preference is stored in a static variable, which is initialized in the static
constructor. This field is declared as read-only, which means that its value can only be set in a constructor.
You learn about read-only fields in more detail later in this chapter. The code uses a few helpful structs that
Microsoft has supplied as part of the Framework class library: System.DateTime and System.Drawing.
Color. DateTime implements a static property — Now, which returns the current time — and an instance
property — DayOfWeek, which works out what day of the week a date-time represents. Color (which is
discussed in the online Chapter 48, “Graphics with GDI+”) is used to store colors. It implements various
static properties, such as Red and Green as used in this example, which returns commonly used colors. To
use Color, you need to reference the System.Drawing.dll assembly when compiling, and you must add a
using statement for the System.Drawing namespace:
using System;
using System.Drawing;
You test the static constructor with this code:
class MainEntryPoint
{
static void Main(string[] args)
{
Console.WriteLine("User-preferences: BackColor is: " +
UserPreferences.BackColor.ToString());
}
}
Compiling and running this code results in this output:
User-preferences: BackColor is: Color [Red]
Of course if the code is executed during the weekend, your color preference would be Green.
Calling Constructors from Other Constructors
You may sometimes find yourself in the situation where you have several constructors in a class, perhaps
to accommodate some optional parameters for which the constructors have some code in common. For
example, consider this:
class Car
{
private string description;
private uint nWheels;
public Car(string description, uint nWheels)
{
this.description = description;
this.nWheels = nWheels;
}
public Car(string description)
{
this.description = description;
this.nWheels = 4;
}
// etc.
Both constructors initialize the same fields. It would clearly be neater to place all the code in one place. C#
has a special syntax known as a constructor initializer to allow this:
class Car
{
private string description;
private uint nWheels;
public Car(string description, uint nWheels)
{
this.description = description;
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