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this article is from a book named<thinking in c#>,if you are interested in the book,you'd better to have a real book made by paper :)

Thinking in C#

Larry O’Brien and Bruce Eckel












Prentice Hall
Upper Saddle River, New Jersey 07458
www.phptr.com

begin:

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This appendix contains suggestions to help guide you in performing low-level program design, and in writing code.

Naturally, these are guidelines and not rules. The idea is to use them as inspirations, and to remember that there are occasional situations where you need to bend or break a rule.

Design
1. Elegance always pays off. In the short term it might seem like it takes much longer to come up with a truly graceful solution to a problem, but when it works the first time and easily adapts to new situations instead of requiring hours, days, or months of struggle, you’ll see the rewards (even if no one can measure them). Not only does it give you a program that’s easier to build and debug, but it’s also easier to understand and maintain, and that’s where the financial value lies. This point can take some experience to understand, because it can appear that you’re not being productive while you’re making a piece of code elegant. Resist the urge to hurry; it will only slow you down.





1. First make it work, then make it fast. This is true even if you are certain that a piece of code is really important and that it will be a principal bottleneck in your system. Don’t do it. Get the system going first with as simple a design as possible. Then if it isn’t going fast enough, profile it. You’ll almost always discover that “your” bottleneck isn’t the problem. Save your time for the really important stuff.

2. Remember the “divide and conquer” principle. If the problem you’re looking at is too confusing, try to imagine what the basic operation of the program would be, given the existence of a magic “piece” that handles the hard parts. That “piece” is an object—write the code that uses the object, then look at the object and encapsulate its hard parts into other objects, etc.

3. Separate the class creator from the class user (client programmer). The class user is the “customer” and doesn’t need or want to know what’s going on behind the scenes of the class. The class creator must be the expert in class design and write the class so that it can be used by the most novice programmer possible, yet still work robustly in the application. Library use will be easy only if it’s transparent.

4. When you create a class, attempt to make your names so clear that comments are unnecessary. Your goal should be to make the client programmer’s interface conceptually simple. To this end, use method overloading when appropriate to create an intuitive, easy-to-use interface.

5. Your analysis and design must produce, at minimum, the classes in your system, their public interfaces, and their relationships to other classes, especially base classes. If your design methodology produces more than that, ask yourself if all the pieces produced by that methodology have value over the lifetime of the program. If they do not, maintaining them will cost you. Members of development teams tend not to maintain anything that does not contribute to their productivity; this is a fact of life that many design methods don’t account for.

6. Automate everything. Write the test code first (before you write the class), and keep it with the class. Automate the running of your tests through a makefile or similar tool. This way, any changes can be automatically verified by running the test code, and you’ll immediately discover errors. Because you know that you have the safety net of your test framework, you will be bolder about making sweep