2. C Language Review

8/2/2019 2. C Language Review

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C# language


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Introduction C# is the programming language for

.Net developer

C# is much safer and simpler It has a visual interface and powerful

editor that provide tons of help

C# is a powerful, professionallanguage, but learning it doesnt haveto be boring


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Basic C# concepts


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Identifiers

used to denote variables, constants,types, methods, objects...

The same to java, c/c++

Note: @+keyword

string @if = "@if";


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Table 2.1: C# Keywords (Reserved Identifiers)

abstract do in protected true

as double int public try

base else interface readonly typeof

bool enum internal ref uint

break event is return ulong

byte explicit lock sbyte unchecke

dcase extern long sealed unsafecatch false namespace short ushort

char finally new sizeof using

checked fixed null stackalloc virtual

class float object static void

const for operator string volatile

continue foreach out struct while

decimal goto override switch

default if params this

delegate implicit private throw


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VariablesAvariablecombines a type with a way to

store a value of the specified type

Example

int theInt;

string deeFlat = "This is a string!";

int i = new int();//int inherit from objectNote: variables be assigned a value before they are used


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Constants

Constantsare declared in C# using theconst keyword followed by the

constant's typeconst float PI = 3.141592;

const string className = QL;


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Enumeration Constants

enum toys {train, dinosaur, truck};

Enumerator Value

toys.train 0

toys.dinosaur 1toys.truck 2

enum toys {train = 12, dinosaur = 35, truck = 42};

Enumerator Valuetoys.train 12

toys.dinosaur 35

toys.truck 42

int x = (int) toys.truck;


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Keyword .NET Type Bytes Description

byte System.Byte 1 (0 to 255).

char System.Char 1 Unicode character.

bool System.Boolean 1 either true or false.

sbyte System.Sbyte 1 (

128 to 127).

short System.Int16 2 (32,768 to 32,767).

ushort System.Uint16 2 (0 to 65,535).

Types(1)


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Types(2)

int System.Int32 4 2147483647 to 2147483647

uint System.Uint32 4 (0 to 4,294,967,295).

float System.Single 4 Single-precision floating point

double System.Double 8 Double-precision floating.

decimal System.Decimal 8 Fixed-precision number up to

28 digits

long System.Int64 8 Signed 64-bit integer.ulong System.Uint64 8 Unsigned 64-bit integer.

object System.Object N/A System.Object class

string System.String N/A Unicode characters.


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Types(3) C# Is a Strongly Typed Language

("type safety").1. Dim theFloat As Double = 3.5

Dim X As Integer = 2

X = X + theFloat =>OK in VB

2. double theFloat = 3.5;

int X = 2;

X = X + theFloat; =>ERROR in C#

3. double theFloat = 3.5;

int X = 2;

X = X + (int) theFloat; => OK


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Commenting Code

// I am a comment!

double theNumber = 3.1415; // other

comment...

/* I am a comment! */

/* I

am another

comment! */


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Operator(1)Operator Arithmetic Meaning

+ Addition.- Subtraction.

* Multiplication.

/ Division.

% Modulus.Logical (Boolean and Bitwise)

& AND.

| OR.

^ Exclusive OR.

! NOT.

~ Bitwise complement.

&& Conditional AND

|| Conditional OR


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Operator(2)String Concatenation

+ Concatenates two strings.

Increment, Decrement

++ Increments operand by 1-- Decrements operand by 1

Comparison

== Equality.

!= Inequality.< Less than.

> Greater than.

= Greater than or equal.


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Operator(3)String Concatenation

+ Concatenates two strings.

Increment, Decrement

++ Increments operand by 1-- Decrements operand by 1

Comparison

== Equality.

!= Inequality.< Less than.

> Greater than.

= Greater than or equal.


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Operator(4)

Assignment

= Assigns the value of the right to the left

+= Addition assignment.-= Subtraction assignment.

Assignment

*= Multiplication assignment.

/= Division assignment.%= Modulus assignment.

&= AND assignment.

|= OR assignment.

^= Exclusive OR assignment.


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Operator(5)

Member Access

. used to access members of a type.

Indexing

[ ] Array indexing (square brackets are also

used to specify attributes).

Casting

( ) Conversion

as The as Operator

Conditional

?: Conditional operator


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Flow Control Statements

The same to java, c/c++

string className = "";

int year;

switch (className) {// string type

case QL04": year =1;break;

case QL03": year = 2;break;

}


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Structs

a simple user-defined type

contain properties, methods, and fields

do not support inheritance

structs derive from System.Object, like alltypes in C#

cannot inherit from any other class (orstruct), and no class or struct can derivefrom a struct.


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Structs

public struct Employee {

public string fullName, rank;

public Employee (string fullName, string rank){this.fullName = fullName;

this.rank = rank;

}}


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Structs

// Declare an instance

Employee A;

// InitializeA.fullName = Nguyen Van A";

OR

A.rank = Manager";

Employee B = new Employee(Nguyen Van B",Staff");


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Exception

The C# Exception object is used tostore information about errors and

abnormal events. trycatchfinallyStatements

finally blocks to close open files and

database connections, and generally tomake sure that all resources used by aprogram are released


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String

Study and present String andStringBuilderProperties and Methods

Dynamic Strings

System.Text.StringBuilder class allows youto create dynamic strings.

may be modified directly

Note: the difference between two class
http://string_property.doc/http://string_property.doc/


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OOP

Declaring a Class

[access-modifier] class class-name{class-body}

public class Car { // declare the fieldspublic string make; public string model;

public string color; public int yearBuilt;

// define the methods

public void Start() {System.Console.WriteLine(model + " started");

}

}


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Creating Objects

The following statements create a Car object:

Car myCar;myCar = new Car();

myCar.make = "Porsche";

myCar .model = "Boxster";

myCar .color = "red";

myCar .yearBuilt = 2000;


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Defining Methods

[access-modifier] return-type method-name

( [parameter-typeparameter-name[, ...]] )

{method-body}


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Defining Properties

public class Car {// declare a private fieldprivate string make;

// declare a propertypublic string Make {get { return make; }

set { make = value; }}}


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Access Modifiers Access

Access Modifier Accessibility

public without restriction.

protected internal only accessible within the class,

a derived class, or class in the

same program

internal only accessible within the class

or class in the same program

protected only accessible within the class

or derived classes.

private only accessible within the class.

This is the default.


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Using Constructors

public class Car {

public() { System.Console.WriteLine("In

Car() constructor");

}

}


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Using Destructors

public class Car {

// define the destructor

~Car() {

// do any cleaning up here

}}


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Introducing Inheritance

public class MotorVehicle {public string model;public MotorVehicle(string model) {

this.model = model;}public void Start() {Console.WriteLine(model + " started");

}}


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Inheritance(cont)

public class Car : MotorVehicle {

bool convertible;

public Car(string model, bool convertible) : base(model)// calls the base class constructor

{

this.convertible = convertible;

}}


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Polymorphism

Polymorphismin a class(Overload) meansthat a class can do the same thing in different

ways. Methods with different parametersignatures offer one form of polymorphism.

Polymorphism in classes(Override) meansthat several classes can have the same

method, but that method happens differentlyin each class


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Overload

In a class

public double getSquare(double theNumber){

return(theNumber * theNumber);} // end getSquare

public double getSquare(int theNumber){

return (int)(theNumber * theNumber);

} // end getSquare


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Override

public class MotorVehicle {

// define the Accelerate() method (may

be overridden in a derived class)public virtual void Accelerate() {Console.WriteLine(model + "

accelerating");}

}


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public class Car : MotorVehicle {

// override Accelerate() method

public override void Accelerate() {Console.WriteLine("Pushing gas pedal of " +model);

// calls the base class Accelerate() method

base.Accelerate();}

}

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2. C Language Review