Tài liệu The System.Object Class ppt

The System.Object Class
One of the most important reference types in the .NET Framework is the Object class in
the System namespace. To fully appreciate the significance of the System.Object class
requires that you understand inheritance, which is described in Chapter 12, “Working
with Inheritance.” For the time being, simply accept that all classes are specialized types
of System.Object, and that you can use System.Object to create a variable that can refer
to any reference type. System.Object is such an important class that C# provides the
object keyword as an alias for System.Object. In your code, you can use object or you
can write System.Object; they mean exactly the same thing.
TIP
Use the object keyword in preference to System.Object. It's more direct and it's also
consistent with using other keywords that have longer synonyms, as you'll discover in
Chapter 9, “Creating Value Types with Enumerations and Structs.” If your program
contains a using System; directive, you could also write Object with a capital O (without
the System. prefix), but it's best to consistently use the simpler keyword object.
In the following example, the variables c and o both refer to the same Circle object. The
fact that the type of c is Circle and the type of o is object (the alias for System.Object) in
effect provides two different views of the same object:
Circle c;
c = new Circle(42);

object o; o = c;