1. Module 5: Common Type System

2. Overview An Introduction to the Common Type System
Elements of the Common Type System
Object-Oriented Characteristics

3. An Introduction to the Common Type System
Common Type System Architecture
Value Types vs. Reference Types

4. Common Type System Architecture
CLR Type System
Value Types
(System.ValueType)
Fields
Methods
Properties
Reference Types
(System.Object)
Built-in Types
Primitive Types
Delegates
Built-in Types
User-defined
Value and Reference Types
Interface Types
Contract specifying
method and property signature

5. Value Types vs. Reference Types
Value Types Are Primitive or User-Defined Structures
Allocated on stack
Assigned as copies
Default behavior is pass by value
Reference Types Are Objects That Are:
Allocated on heap using the new keyword
Assigned as references
Passed by reference

6. Elements of the Common Type System
Primitive Types
Objects
Constructors
Properties
Custom Types
Enumerations
Interfaces

7. Primitive Types Simple Small Types Common in Most Languages
Naming Differences
C# Support
Conversions

8. Objects Every Class Inherits from System.Object
Objects Specify Data and Behavior
Fields Define the Data
Methods Define the Behavior
class Accumulator {
public float Result;
public void Add(float amount)
Result += amount; }

9. Constructors Constructors Are Used to Initialize Classes
Constructors Can Have Zero or More Parameters
class Rectangle {
private int x1,y1,x2,y2;
public Rectangle(int x1, int y1, int x2,int y2)
this.x1 = x1;
this.x2 = x2;
this.y1 = y1;
this.y2 = y2; }

10. Properties Properties Are Similar to Fields
Properties Use get and set Accessor Methods for Managing Data Values
public float Start {
get
return start; }
set
if (start >= 0) start = value;

11. Custom Types Inherit from System.ValueType
Are Defined with the struct Keyword in C#
Can Have Methods, Properties, and Fields
struct Employee {
public string Name;
public ushort Age;
public DateTime HireDate;
public float Tenure()
TimeSpan ts = DateTime.Now – HireDate;
return ts.Days/(float)365; }

12. Enumerations .NET Framework Enumerations Inherit from System.Enum
Use the enum keyword
Bit Flags
enum SeatPreference : ushort {
Window, //Assigned value 0
Center, //Assigned value 1
Aisle //Assigned value 2 }

13. Interfaces
An Interface Is a Contractual Description of Methods and Properties
An Interface Has No Implementation
Use Casting in Client Code to Use an Interface
interface ICDPlayer {
void Play(short playTrackNum);
void Pause();
void Skip(short numTracks);
short CurrentTrack
get;
set; }

14. Object-Oriented Characteristics
Abstraction
Encapsulation
Inheritance
Polymorphism

15. Abstraction Abstraction Works from the Specific to the General
Grouping Elements Makes It Easier to Work with Complex Data Types
Abstraction Is Supported Through Classes

16. Encapsulation
Encapsulation Is the Process of Hiding Internal Details of a Class
Encapsulation Keywords
public
protected
internal
private
Type-Level Accessibility
Nested Classes

17. Inheritance Inheritance Is the Reuse of Class Members in Other Classes
The Common Type System Only Supports Single Inheritance for Classes
Member Hiding
Redefine the same method in the derived class
Use the new keyword
Abstract Members
Sealed Classes

18. Polymorphism
Polymorphism Allows a Reference Variable to Call the Correct Method
Virtual Methods Enable Polymorphism in the Common Type System
Use the virtual keyword in the base class
Use the override keyword in the derived class
Sealed Methods

19. Lab 5: Building Simple Types

20. Review An Introduction to the Common Type System
Elements of the Common Type System
Object-Oriented Characteristics