0.3 Xna0104-what is oop and why should you care?  (Page 7/7)

As long as it won't create name conflicts, you can tell the compiler that you are "using" the namespace as shown by the first line following the initial commentin Listing 2 . Then you don't need to refer to the namespace when you reference a class belonging to that namespace in your code.

Not much help in this case

In this case, since the Console class was referenced only once, it would have been simpler to join the class name with the namespace nameusing the dot operator and to omit the "using" declaration. However, in those cases where the class name is referenced more than once in the code, it issimpler to declare the namespace at the beginning to avoid having to type it more than once. This is particularly true in the case of the SpriteBatch class shown above where thenamespace name contains several levels separated by periods.

Defining your own namespace

When you define a new class, you should always define the namespace in which it resides. (I believe this is a requirement when developing projects using Visual C#.)

The project file structure

Figure 1 shows the project file structure for the Hello01 project. ( Figure 1 was captured from the Solution Explorer window in the Visual C# IDE.)

Figure 1 . Project file structure.

The class definition shown in Listing 2 is contained in the file named Program.cs at the bottom of the tree in Figure 1 . Note that this file is contained in the folder named Hello01 . Also note that the folder named Hello01 is a child of another folder named Hello01 at the top of the project tree. (There are two folders named Hello01 in the project tree.)

The Hello01 namespace

The second line following the initial comment in Listing 2 defines the namespace in which the new class resides. Note that it is the name of the folder in whichthe file resides. Note also that it is specified relative to the top of the project tree.

If the folder containing the class happened to be more than one level down in the project tree, as is the case of the Graphics folder that contains the SpriteBatch class, it would be necessary to use periods to trace down the tree.

The call to the ReadKey method

Listing 2 also contains a call to a method named ReadKey , which also belongs to the Console class. The purpose of this call is to cause the execution of the program to block and wait until the userpresses any key. Otherwise, the console window would appear on the computer screen momentarily and then disappear almost as soon as it appears.

Run the program

I encourage you to copy the code from Listing 2 . Use that code to create a Visual C# Console Application project. Build and run the project. Experiment with the code, making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as theydo.

Run my program

Click here to download a zip file containing my version of the program. Extract the folder named Hello01 from the zip file and save it somewhere on your disk. Start Visual C# 2010 Express and select Open Project... from the File menu. Navigate to the project folder and select the file with the extension of .sln . This should cause the project to open and be ready to run or debug as describedin the earlier module titled Getting Started .

Summary

You learned something about object-oriented programming in general in this module. You also learned quite a bit about the structure and syntax of anobject-oriented C# program by taking a simple program apart and examining the elements of the program.

Miscellaneous

This section contains a variety of miscellaneous information.

-end-