![Properties – syntax examples
type PropertyName { get; set; }
Many valid formats
int Score { get; set; }
string Name { get; }
double Time { get; private set; }
Code examples
◦ Person*.cs examples [Compare maintainability]
◦ http://www.dotnetperls.com/property](https://image.slidesharecdn.com/csharp-240128203638-6525e113/85/CSharp-presentation-and-software-developement-20-320.jpg)
CSharp presentation and software developement
- 1. Notes on C# BY: MATT BOGGUS SOME MATERIAL BASED ON ROGER CRAWFIS’ C# SLIDES
- 2. C# and Java similarities All classes are objects ◦ Compare System.Object to java.lang.Object Similar compilation and runtime to Java ◦ Compare Java Virtual Machine to Common Language Runtime Heap-based allocation ◦ Use “new” keyword to instantiate ◦ Automatic garbage collection
- 3. C# language features Namespaces Classes ◦ Fields ◦ Properties ◦ Methods ◦ Events Structs Enums Interfaces ◦ Methods ◦ Properties ◦ Events Control Statements ◦ if, else, while, for, switch, foreach
- 5. Classes vs. structs Both are user-defined types Both can implement multiple interfaces Both can contain ◦ Data ◦ Fields, constants, events, arrays ◦ Functions ◦ Methods, properties, indexers, operators, constructors ◦ Type definitions ◦ Classes, structs, enums, interfaces, delegates
- 6. Classes vs. structs CLASS ; REFERENCE TYPE Reference type Original instance of the object can be modified during execution of method bodies STRUCT ; VALUE TYPE Value type A copy of the object is made and operated on inside method bodies Many types in XNA and MonoGame are defined as structs (ex: Vector2 and Rectangle) Can pass structs as reference type using ‘ref’ keyword
- 7. Interfaces
- 8. Interfaces An interface defines a contract ◦ An interface is a type ◦ Contain definitions for methods, properties, indexers, and/or events ◦ Any class or struct implementing an interface must support all parts of the contract Interfaces provide no implementation ◦ When a class or struct implements an interface it must provide the implementations ◦ SOLID: Depend upon abstractions not concretions
- 9. Interfaces “Rigid” interface ◦ Functionality is explicitly defined ◦ Ex: OSU Component Library where interfaces include Javadoc comments with methods’ requires and ensures clauses (pre and post conditions) “Flexible” interface ◦ Only method signatures are specified ◦ Ex: IBird interface defines void Fly() Duck class implements void Fly { position.y += 5; } Penguin class implements void Fly { // no-op }
- 10. public interface IDelete { void Delete(); } public class TextBox : IDelete { public void Delete() { ... } } public class ImageBox : IDelete { public void Delete() { ... } } TextBox tb = new TextBox(); tb.Delete(); Interface example IDelete deletableObj = new ImageBox(); deletableObj.Delete(); deletableObj = new TextBox(); deletableObj.Delete();
- 11. Abstract Classes
- 12. Abstract class Similar to interfaces ◦ Cannot be instantiated ◦ In some cases, contain no executable code ◦ Can contain method headers/signatures and properties (more on these in a bit), but unlike interfaces they can contain concrete elements like method bodies and fields Some quirks when working with abstract classes and interfaces ◦ A class that is derived from an abstract class may still implement interfaces ◦ A concrete class may implement an unlimited number of interfaces, but may inherit from only one abstract (or concrete) class
- 13. public abstract class Shape { protected int x = 50; protected int y = 50; public abstract int Area(); } public class Square : Shape { public int width; public int height; public override int Area() { return width * height; } public void MoveLeft() { x--; } } Abstract class example Methods marked as abstract have no bodies and must be overridden Methods marked as virtual have bodies and may be overridden See http://msdn.microsoft.com/en- us/library/sf985hc5.aspx for a longer example
- 14. Class internals
- 15. this The this keyword is a predefined variable available in non-static function members ◦ Used to access data and function members unambiguously public class Person { private string name; public Person(string name) { this.name = name; } public void Introduce(Person p) { if (p != this) Console.WriteLine(“Hi, I’m “ + name); } }
- 16. base The base keyword can be used to access class members that are hidden by similarly named members of the current class public class Shape { private int x, y; public override string ToString() { return "x=" + x + ",y=" + y; } } public class Circle : Shape { private int r; public override string ToString() { return base.ToString() + ",r=" + r; } }
- 17. Fields A field or member variable holds data for a class or struct Can hold: ◦ A built-in value type ◦ A class instance (a reference) ◦ A struct instance (actual data) ◦ An array of class or struct instances (an array is actually a reference) ◦ An event
- 18. Field examples static and instance Output is: 20 2 30 2 public class NumStore { public static int i = 10; public int j = 1; public void AddAndPrint() { i=i+10; j=j+1; Console.WriteLine(i); Console.WriteLine(j); } } public class Exercise { static void Main() { NumStore x = new NumStore(); x.AddAndPrint(); NumStore y = new NumStore(); y.AddAndPrint(); Console.ReadKey(); } }
- 19. Properties Client side looks like a field Internally behaves like method calls to get or set the field (i.e. more abstract than a field) Properties encapsulate a getting and setting a field ◦ Useful for changing the internal type for a field ◦ Useful for adding code or breakpoints when getting/setting a field
- 20. Properties – syntax examples type PropertyName { get; set; } Many valid formats int Score { get; set; } string Name { get; } double Time { get; private set; } Code examples ◦ Person*.cs examples [Compare maintainability] ◦ http://www.dotnetperls.com/property
- 21. Modifiers Public ◦ Accessible anywhere Protected ◦ Accessible within its class and by derived class instances Private ◦ Accessible only within the body of the class ◦ (Or anywhere if you use reflection) Internal ◦ Intuitively, accessible only within this program (more specific definition here) ◦ The default, but you should generally pick public or private instead
- 22. Access modifier error example Cannot have an interface that is less accessible than a concrete class that implements it (also applies to base and inheriting classes) interface GameObject // no access modifier, defaults to internal { void Draw(); void Update(); } public class Monster : GameObject { // ... implementations of Draw() and Update() go here ... }
- 23. End of lecture ADDITIONAL ON YOUR OWN SLIDES FOLLOW
- 24. Why C#? Fits with ◦ .NET framework ◦ Large library of features and objects; portable and integrates with software written in other languages ◦ Visual Studio ◦ Single point of access for software development, source code control, project management, and code reviews Additional reasons ◦ Game engines support C# -> XNA, Monogame, Unity ◦ Used in other CSE graphics courses (Game and Animation Techniques; Game Capstone) ◦ More discussion of pros/cons of C# here ◦ More discussion of pros/cons of C# specific to game development here; this subset of comments has some good insights
- 25. On your own Java to C# resources The C# Programming Language for Java Developers – documentation of language differences organized by programming constructs Additional Suggestions from StackOverflow
- 26. public class Car : Vehicle { public enum Make { GM, Honda, BMW } private Make make; private string vid; private Point location; Car(Make make, string vid, Point loc) { this.make = make; this.vid = vid; this.location = loc; } public void Drive() { Console.WriteLine(“vroom”); } } Car c = new Car(Car.Make.BMW, “JF3559QT98”, new Point(3,7)); c.Drive(); Class syntax example
- 27. How many methods should classes/interfaces provide? On your own references Keep it simple! ◦ The Magical Number Seven, Plus or Minus Two ◦ The average person can hold 7 ± 2 objects in memory at a time ◦ Experts recall more by “chunking” – combining multiple objects into one ◦ Think You're Multitasking? Think Again ◦ The average person is bad at multi-tasking, so focus on what you’re doing if you want it done well
- 28. Conversion
- 29. Conversion operators Can also specify user-defined explicit and implicit conversions public class Note { private int value; // Convert to hertz – no loss of precision public static implicit operator double(Note x) { return ...; } // Convert to nearest note public static explicit operator Note(double x) { return ...; } } Note n = (Note)442.578; double d = n;
- 30. The is Operator The is operator is used to dynamically test if the run-time type of an object is compatible with a given type private static void DoSomething(object o) { if (o is Car) ((Car)o).Drive(); }
- 31. The as Operator The as operator tries to convert a variable to a specified type; if no such conversion is possible the result is null More efficient than using is operator ◦ Can test and convert in one operation private static void DoSomething(object o) { Car c = o as Car; if (c != null) c.Drive(); }