- •Microsoft C# Programming for the Absolute Beginner
- •Table of Contents
- •Microsoft C# Programming for the Absolute Beginner
- •Introduction
- •Overview
- •Chapter 1: Basic Input and Output: A Mini Adventure
- •Project: The Mini Adventure
- •Reviewing Basic C# Concepts
- •Namespaces
- •Classes
- •Methods
- •Statements
- •The Console Object
- •.NET Documentation
- •Getting into the Visual Studio .Net Environment
- •Examining the Default Code
- •Creating a Custom Namespace
- •Adding Summary Comments
- •Creating the Class
- •Moving from Code to a Program
- •Compiling Your Program
- •Looking for Bugs
- •Getting Input from the User
- •Creating a String Variable
- •Getting a Value with the Console.ReadLine() Method
- •Incorporating a Variable in Output
- •Combining String Values
- •Combining Strings with Concatenation
- •Adding a Tab Character
- •Using the Newline Sequence
- •Displaying a Backslash
- •Displaying Quotation Marks
- •Launching the Mini Adventure
- •Planning the Story
- •Creating the Variables
- •Getting Values from the User
- •Writing the Output
- •Finishing the Program
- •Summary
- •Chapter 2: Branching and Operators: The Math Game
- •The Math Game
- •Using Numeric Variables
- •The Simple Math Game
- •Numeric Variable Types
- •Integer Variables
- •Long Integers
- •Data Type Problems
- •Math Operators
- •Converting Variables
- •Explicit Casting
- •The Convert Object
- •Creating a Branch in Program Logic
- •The Hi Bill Game
- •Condition Testing
- •The If Statement
- •The Else Clause
- •Multiple Conditions
- •Working with The Switch Statement
- •The Switch Demo Program
- •Examining How Switch Statements Work
- •Creating a Random Number
- •Introducing the Die Roller
- •Exploring the Random Object
- •Creating a Random Double with the .NextDouble() Method
- •Getting the Values of Dice
- •Creating the Math Game
- •Designing the Game
- •Creating the Variables
- •Managing Addition
- •Managing Subtraction
- •Managing Multiplication and Division
- •Checking the Answers
- •Waiting for the Carriage Return
- •Summary
- •Chapter 3: Loops and Strings: The Pig Latin Program
- •Project: The Pig Latin Program
- •Investigating The String Object
- •The String Mangler Program
- •A Closer Look at Strings
- •Using the Object Browser
- •Experimenting with String Methods
- •Performing Common String Manipulations
- •Using a For Loop
- •Examining The Bean Counter Program
- •Creating a Sentry Variable
- •Checking for an Upper Limit
- •Incrementing the Variable
- •Examining the Behavior of the For Loop
- •The Fancy Beans Program
- •Skipping Numbers
- •Counting Backwards
- •Using a Foreach Loop to Break Up a Sentence
- •Using a While Loop
- •The Magic Word Program
- •Writing an Effective While Loop
- •Planning Your Program with the STAIR Process
- •S: State the Problem
- •T: Tool Identification
- •A: Algorithm
- •I: Implementation
- •R: Refinement
- •Applying STAIR to the Pig Latin Program
- •Stating the Problem
- •Identifying the Tools
- •Creating the Algorithm
- •Implementing and Refining
- •Writing the Pig Latin Program
- •Setting Up the Variables
- •Creating the Outside Loop
- •Dividing the Phrase into Words
- •Extracting the First Character
- •Checking for a Vowel
- •Adding Debugging Code
- •Closing Up the code
- •Summary
- •Introducing the Critter Program
- •Creating Methods to Reuse Code
- •The Song Program
- •Building the Main() Method
- •Creating a Simple Method
- •Adding a Parameter
- •Returning a Value
- •Creating a Menu
- •Creating a Main Loop
- •Creating the Sentry Variable
- •Calling a Method
- •Working with the Results
- •Writing the showMenu() Method
- •Getting Input from the User
- •Handling Exceptions
- •Returning a Value
- •Creating a New Object with the CritterName Program
- •Creating the Basic Critter
- •Using Scope Modifiers
- •Using a Public Instance Variable
- •Creating an Instance of the Critter
- •Adding a Method
- •Creating the talk() Method for the CritterTalk Program
- •Changing the Menu to Use the talk() Method
- •Creating a Property in the CritterProp Program
- •Examining the Critter Prop Program
- •Creating the Critter with a Name Property
- •Using Properties as Filters
- •Making the Critter More Lifelike
- •Adding More Private Variables
- •Adding the Age() Method
- •Adding the Eat() Method
- •Adding the Play() Method
- •Modifying the Talk() Method
- •Making Changes in the Main Class
- •Summary
- •Introducing the Snowball Fight
- •Inheritance and Encapsulation
- •Creating a Constructor
- •Adding a Constructor to the Critter Class
- •Creating the CritViewer Class
- •Reviewing the Static Keyword
- •Calling a Constructor from the Main() Method
- •Working with Multiple Files
- •Overloading Constructors
- •Viewing the Improved Critter Class
- •Adding Polymorphism to Your Objects
- •Modifying the Critter Viewer in CritOver to Demonstrate Overloaded Constructors
- •Using Inheritance to Make New Classes
- •Creating a Class to View the Clone
- •Creating the Critter Class
- •Improving an Existing Class
- •Introducing the Glitter Critter
- •Adding Methods to a New Class
- •Changing the Critter Viewer Again
- •Creating the Snowball Fight
- •Building the Fighter
- •Building the Robot Fighter
- •Creating the Main Menu Class
- •Summary
- •Overview
- •Introducing the Visual Critter
- •Thinking Like a GUI Programmer
- •Creating a Graphical User Interface (GUI)
- •Examining the Code of a Windows Program
- •Adding New Namespaces
- •Creating the Form Object
- •Creating a Destructor
- •Creating the Components
- •Setting Component Properties
- •Setting Up the Form
- •Writing the Main() Method
- •Creating an Interactive Program
- •Responding to a Simple Event
- •Creating and Adding the Components
- •Adding an Event to the Program
- •Creating an Event Handler
- •Allowing for Multiple Selections
- •Choosing a Font with Selection Controls
- •Creating the User Interface
- •Examining Selection Tools
- •Creating Instance Variables in the Font Chooser
- •Writing the AssignFont() Method
- •Writing the Event Handlers
- •Working with Images and Scroll Bars
- •Setting Up the Picture Box
- •Adding a Scroll Bar
- •Revisiting the Visual Critter
- •Designing the Program
- •Determining the Necessary Tools
- •Designing the Form
- •Writing the Code
- •Summary
- •Chapter 7: Timers and Animation: The Lunar Lander
- •Introducing the Lunar Lander
- •Reading Values from the Keyboard
- •Introducing the Key Reader Program
- •Setting Up the Key Reader Program
- •Coding the KeyPress Event
- •Coding the KeyDown Event
- •Determining Which Key Was Pressed
- •Animating Images
- •Introducing the ImageList Control
- •Setting Up an Image List
- •Looking at the Image Collection
- •Displaying an Image from the Image List
- •Using a Timer to Automate Animation
- •Introducing the Timer Control
- •Configuring the Timer
- •Adding Motion
- •Checking for Keyboard Input
- •Working with the Location Property
- •Detecting Collisions between Objects
- •Coding the Crasher Program
- •Getting Values for newX and newY
- •Bouncing the Ball off the Sides
- •Checking for Collisions
- •Extracting a Rectangle from a Component
- •Getting More from the MessageBox Object
- •Introducing the MsgDemo Program
- •Retrieving Values from the MessageBox
- •Coding the Lunar Lander
- •The Visual Design
- •The Constructor
- •The timer1_Tick() Method
- •The moveShip() Method
- •The checkLanding() Method
- •The theForm_KeyDown() Method
- •The showStats() Method
- •The killShip() Method
- •The initGame() Method
- •Summary
- •Chapter 8: Arrays: The Soccer Game
- •The Soccer Game
- •Introducing Arrays
- •Exploring the Counter Program
- •Creating an Array of Strings
- •Referring to Elements in an Array
- •Working with Arrays
- •Using the Array Demo Program to Explore Arrays
- •Building the Languages Array
- •Sorting the Array
- •Designing the Soccer Game
- •Solving a Subset of the Problem
- •Adding Percentages for the Other Players
- •Setting Up the Shot Demo Program
- •Setting Up the List Boxes
- •Using a Custom Event Handler
- •Writing the changeStatus() Method
- •Kicking the Ball
- •Designing Programs by Hand
- •Examining the Form by Hand Program
- •Adding Components in the Constructor
- •Responding to the Button Event
- •Building the Soccer Program
- •Setting Up the Variables
- •Examining the Constructor
- •Setting Up the Players
- •Setting Up the Opponents
- •Setting Up the Goalies
- •Responding to Player Clicks
- •Handling Good Shots
- •Handling Bad Shots
- •Setting a New Current Player
- •Handling the Passage of Time
- •Updating the Score
- •Summary
- •Chapter 9: File Handling: The Adventure Kit
- •Introducing the Adventure Kit
- •Viewing the Main Screen
- •Loading an Adventure
- •Playing an Adventure
- •Creating an Adventure
- •Reading and Writing Text Files
- •Exploring the File IO Program
- •Importing the IO Namespace
- •Writing to a Stream
- •Reading from a Stream
- •Creating Menus
- •Exploring the Menu Demo Program
- •Adding a MainMenu Object
- •Adding a Submenu
- •Setting Up the Properties of Menu Items
- •Writing Event Code for Menus
- •Using Dialog Boxes to Enhance Your Programs
- •Exploring the Dialog Demo Program
- •Adding Standard Dialogs to Your Form
- •Using the File Dialog Controls
- •Responding to File Dialog Events
- •Using the Font Dialog Control
- •Using the Color Dialog Control
- •Storing Entire Objects with Serialization
- •Exploring the Serialization Demo Program
- •Creating the Contact Class
- •Referencing the Serializable Namespace
- •Storing a Class
- •Retrieving a Class
- •Returning to the Adventure Kit Program
- •Examining the Room Class
- •Creating the Dungeon Class
- •Writing the Game Class
- •Writing the Editor Class
- •Writing the MainForm Class
- •Summary
- •Chapter 10: Chapter Basic XML: The Quiz Maker
- •Introducing the Quiz Maker Game
- •Taking a Quiz
- •Creating and Editing Quizzes
- •Investigating XML
- •Defining XML
- •Creating an XML Document in .NET
- •Creating an XML Schema for Your Language
- •Investigating the .NET View of XML
- •Exploring the XmlNode Class
- •Exploring the XmlDocument Class
- •Reading an Existing XML Document
- •Creating the XML Viewer Program
- •Writing New Values to an XML Document
- •Building the Document Structure
- •Adding an Element to the Document
- •Displaying the XML Code
- •Examining the Quizzer Program
- •Building the Main Form
- •Writing the Quiz Form
- •Writing the Editor Form
- •Summary
- •Overview
- •Introducing the SpyMaster Program
- •Creating a Simple Database
- •Accessing the Data Server
- •Accessing the Data in a Program
- •Using Queries to Modify Data Results
- •Limiting Data with the SELECT Statement
- •Using an Existing Database
- •Adding the Capability to Display Queries
- •Creating a Visual Query Builder
- •Working with Relational Databases
- •Improving Your Data with Normalization
- •Using a Join to Connect Two Tables
- •Creating a View
- •Referring to a View in a Program
- •Incorporating the Agent Specialty Attribute
- •Working with Other Databases
- •Creating a New Connection
- •Converting a Data Set to XML
- •Reading from XML to a Data Source
- •Creating the SpyMaster Database
- •Building the Main Form
- •Editing the Assignments
- •Editing the Specialties
- •Viewing the Agents
- •Editing the Agent Data
- •Summary
- •List of Figures
- •List of Tables
- •List of Sidebars
Figure 4.5: The cost of neglect can be a sad and lifeless critter. Fortunately, with enough food and love, it can be revived.
I used simple rules to drive the critter’s behavior. During each turn, the critter ages and becomes hungrier and a little more unhappy. Whenever you talk to the critter, it gives you a message based on its current happiness level. If the critter is hungry, it becomes unhappy even more quickly. Playing with and feeding the critter make it happier. That’s all there is to the design of the critter, but to create the program, I relied on OOP techniques. The critter is actually an object, and it can talk, eat, play, and age.
Another interesting feature of the Critter program is the use of a simple menu. Many console−based programs use a menu, so now you’ll learn how to build one.
Creating Methods to Reuse Code
As programming has evolved, computer scientists have discovered techniques for making it easier to write and maintain programs. Most of these ideas are borrowed from the outside world and are simple. One of the most important is the notion of encapsulation, another word for grouping together (as already mentioned, computer scientists like to give complicated names to simple ideas).
For example, if somebody asked you what you did this weekend, you might reply, “I played with the kids, went shopping, and worked on the house.” You probably would not describe everything you did over the weekend. Instead, you would group several complex activities into one phrase. You would say, “I played with the kids,” without describing all the components of this behavior (which, in my house, involve loud noises, wrestling, Dad’s dressing up in at least one ridiculous outfit, and somebody in tears). All those details are wrapped up in one phrase.
Encapsulation in programming works much the same way. You take groups of instructions and put them together to make methods. These methods are things the object can do. For example, the critter can eat and play. It has Eat and Play methods to enable these behaviors. After you’ve defined a set of instructions as a method, you can refer to the name of the method, and all the code related to that name will execute.
The Song Program
To clarify the concept of encapsulation, I wrote a program that replicates a serious and weighty application of your computer’s horsepower. The Song program repeats the words to the classic
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children’s song This Old Man. In case it has been a while, the words (for the first couple of verses) go like this:
This old man, he played one
He played knick−knack on my thumb
With a knick−knack paddy−whack
Give a dog a bone
This old man came rolling home
This old man, he played two
He played knick−knack on my shoe
With a knick−knack paddy−whack
Give a dog a bone
This old man came rolling home
The song goes along for 10 verses, but the pattern is evident by the second stanza. You can see that most of the verses are almost the same, except that each features a number and the old man plays knick−knack (whatever that means) on something that rhymes with the number. A computerized version of the song is amazingly compact if you think of it in terms of methods.
Building the Main() Method
So far, all the programs in this book have been written entirely in the Main() method. You might be surprised to learn that the Main() method of most programs in C# is very small. Figure 4.6 demonstrates the Main() method for the Song program.
Figure 4.6: The Main() method features a few commands. You can probably guess what each one does.
Like most songs, This Old Man has a pattern: a simple verse that changes and a chorus that stays the same. You can summarize the pattern of the song like this:
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verse 1
chorus
verse 2
chorus
Of course, this summary is much like the main() method. To pull this off, I had to build methods to handle the verses and the chorus, but all the code is delegated to these methods. With the details encapsulated away in various methods, the main() method clearly demonstrates the main flow of the program.
Trick In Figure 4.6, I utilized a feature of the .NET IDE. For this image, I wasn’t interested in the details of any methods except the main() method, so I used the small plus and minus signs along the left margin to collapse and expand the methods I wanted to look at. This is a wonderful tool because it enables you to focus on the parts of the program you’re currently working on, without losing sight of how each part fits into the larger picture.
Of course, the program won’t work exactly like this yet because it is necessary to write the methods. You do that in the next few sections.
Creating a Simple Method
You will start with the doChorus() method because it’s the most straightforward:
static void doChorus(){ string message = "";
message += "\n...With a knick−knack paddy whack\n"; message += "Give a dog a bone\n";
message += "This old man came rolling home."; message += "\n\n"; System.Console.WriteLine(message);
} // end doChorus
Custom methods can begin just like the main() method. I declared the method with
static void doChorus(){
The static keyword defines the method as one that can be called before the class has been completely created. It’s okay if you don’t understand that yet. The concept will make more sense after you learn about constructors and instantiation later in this chapter.
The void keyword indicates that this method will not return any value. Again, you have to take my word for it, but I’ll explain exactly what that means later in this chapter in a section cleverly called "Returning a Value." doChorus() is the name of the method, so all the code in this section is named doChorus, and the main() method can invoke all these commands by simply calling the doChorus() method.
The code inside the method is straightforward. I created a string variable named message, added some values to it to write the chorus, and wrote that message to the screen.
Notice that you can create variables inside a method, as well as inside a class. This is important because a variable lives only as long as the structure in which it’s created. In other words, the
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message variable is created each time the doChorus() method is invoked, but as soon as that method finishes (which takes a fraction of a second), the message variable is destroyed. This is good because you don’t have to worry about the message variable’s interference with other code you’re writing. This local ownership of variables is called data hiding, and it’s another benefit of encapsulation.
In the Real World
A long time ago I wrote a program for a middle school. The program had to be run on Apple IIe machines, so I was required to use an antiquated language that allows only two−character variable names and cannot encapsulate code. I had the program running almost perfectly, but it was doing very strange things at unpredictable intervals. After tearing out my hair for three days, I finally discovered that I had accidentally used the same variable name for two different things. This is exactly the sort of situation that encapsulation and data hiding can prevent.
Adding a Parameter
The doChorus() method is easy to write because it works exactly the same way each time you call it. However, you frequently run into situations more like the verse—you want the program to behave almost the same each time, but you want to send it a value to act upon. Many of the methods you’ve already used (such as Console.WriteLine) work in this way. They expect you to send a value between the parentheses, and then they act on that value. Notice in the main() method that, when I call the doVerse() method, I always include an integer value. It is quite easy to write a method that accepts a value:
static void doVerse(int verseNum){ string message = "";
message += "This old man, he played "; message += verseNum;
message += ". \nHe played knick−knack "; message += getPlace(verseNum); Console.WriteLine(message);
} // end verse
To modify a method so that it can accept a value, put a variable declaration inside the quotes that follow the method’s name. This special variable is called a parameter, and it automatically accepts whatever value was sent when the method was called. For example, when the main() method says doVerse(1), the value of verseNum inside doVerse() is 1. The next time the main() method invokes doVerse(2), the verseNum parameter will have the value 2. You can have as many parameters as you like, but you must indicate the type of parameter you will send, and you must separate the parameters by commas. Parameters have the same kind of limited life span as variables declared inside a method.
Notice that the doVerse() method also has a message variable, but this one is entirely unrelated to the message variable in doChorus().
In the following line, you can see how I used verseNum to integrate the verse number into the verse:
message += verseNum;
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