- •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
Writing New Values to an XML Document
In addition to reading existing documents, .NET makes creating an XML document from scratch very easy. The XML Creator program illustrates how this can be done. Figures 10.14 and 10.15 show the XML Creator program in action. What makes the XML Creator different from the XML Viewer is that the creator program can create XML without a pre−existing document. The XML Creator emphasizes how to create a new document and new nodes.
Figure 10.14: The XML displayed in the right panel was created by the program.
Figure 10.15: After entering a new element in the text boxes, pressing the Add button, and displaying the XML, a new element is visible in the code.
Designating the Class−Level Variables
No new classes are necessary to create an XML document. The program uses an XmlDocument named doc, an XmlNode named theNode, and a string to hold a file name:
private XmlDocument doc; private XmlNode theNode;
private string fileName = "practice.xml";
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Building the Document Structure
The XML document is created in the load method of the form. Creating the document is not difficult because it is simply a new instance of the XmlDocument class. However, creating the structure of the document takes some thought. For the XML Creator, I decided to build a simple address book. Figure 10.16 shows the basic document structure.
Figure 10.16: The document contains a contact, which is a group of person elements. Each person consists of a name, address, and phone number.
Trick It’s a familiar refrain by now, but one that bears repeating. You need to sketch out a diagram like this before you start to code an XML document, or you’re going to get confused. Seeing the relationships between elements in your code can be difficult, but a diagram like this clarifies your intentions and makes the code much easier to write.
The code works by creating XmlElement variables for contact and person. theNode will be used as a temporary node. The first element in any document is the root (xml) node. A special method of the XmlDocument object is designed to simplify the creation of a root node: CreateXmlDeclaration() makes a root node. The parameters are almost always as listed. The first parameter stands for the XML type, which should always be "1.0". The second parameter stands for the encoding, which should always be "utf−8". The last parameter describes whether the document can stand alone. It should be "yes". After you create the root node, you still have to add it to the document. Use the AppendChild() method of the XmlNode class to add a child to a node (or to the document itself, which is also a node).
To create the other elements, use the CreateElement() method of the XmlDocument class. You will still need to use the AppendChild() method of whichever node you want to add the new child to. For example, the following code creates a node named contacts and appends it to the document object:
//create contacts node
contacts = doc.CreateElement("contacts"); doc.AppendChild(contacts);
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The next code fragment creates a person node and adds it as a child to contacts:
//create first address
person = doc.CreateElement("person"); contacts.AppendChild(person);
When the basic structure is in place, it’s time to add some elements to the person class. Each of these elements is created just like contacts and person, but the other elements hold actual data. The easiest way to add information to a node is to set the InnerText property of the node in question. For example, here’s how I set up the name element:
theNode = doc.CreateElement("name"); theNode.InnerText = "Roger Dodger"; person.AppendChild(theNode);
The entire code for the form’s load event shows how the entire document is designed:
private void XmlCreatorForm_Load(object sender,
System.EventArgs e) { //initialize
doc = new XmlDocument();
XmlElement contacts;
XmlElement person;
//create root node
theNode = doc.CreateXmlDeclaration("1.0", "utf−8", "yes"); doc.AppendChild(theNode);
//create contacts node
contacts = doc.CreateElement("contacts"); doc.AppendChild(contacts);
//create first address
person = doc.CreateElement("person"); contacts.AppendChild(person);
//create address elements
theNode = doc.CreateElement("name"); theNode.InnerText = "Roger Dodger"; person.AppendChild(theNode);
theNode = doc.CreateElement("address"); theNode.InnerText = "123 W 4th St."; person.AppendChild(theNode);
theNode = doc.CreateElement("phone"); theNode.InnerText = "123−4567"; person.AppendChild(theNode);
} // end form load
As you can see from the code, it’s possible to create an XML document entirely from scratch, but you must have a solid idea of the document’s structure.
Adding an Element to the Document
You can create additional elements in the same way you create the first one. However, after the basic structure of an element is defined, it’s much easier to make a copy of an existing element than
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to build one from scratch.
The code in btnAdd’s click event illustrates how this is done:
private void btnAdd_Click(object sender, System.EventArgs e) { //duplicate the person node
XmlNode contacts; XmlNode person; XmlNode root;
root = doc.FirstChild; contacts = root.NextSibling; person = contacts.FirstChild; theNode = person.Clone();
//copy node values from text boxes theNode["name"].InnerText = txtName.Text; theNode["address"].InnerText = txtAddress.Text; theNode["phone"].InnerText = txtPhone.Text;
//add the new node to contacts contacts.AppendChild(theNode);
} // end btnAdd
The first part of the code recreates the document’s structure by extracting the root node, the contacts node, and the person node. Next, I created a copy of the person node, named theNode, by using the Clone() method of the person node.
I then copied the values from the text boxes over to the new node. Notice how you can use the node’s name inside braces to specify which node you want to work with.
Finally, I added the new node to contacts.
Trap Keep your diagram handy as you’re adding nodes. The document structure expects all person nodes to be added to the contacts node. You will get unpredictable results if you add the person node somewhere else.
Displaying the XML Code
To see that something is happening, I decided to display the code in the text box. In principle, this is very easy to do. Every node (including doc) has an OuterXml property that returns the XML code of the node and all its children (the InnerXml property returns the XML code of the node’s children, but not the node itself). However, the formatting that is useful for human readers (with carriage returns and indentation) is usually stripped out in the internal representations of XML code because it can confuse the parser (the part of the program that navigates the XML structure). Figure 10.17 illustrates what happens when you simply copy the internal XML to the text box.
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