I HC NNG

TRNG CAO NG CNG NGH THNG TIN

B MN CNG NGH

GIO TRNH

LP TRNH .NET

Dch v tng hp: L Vn Minh

(Lu hnh ni b)

NNG, 07/2008

LI NI U

Gio trnh Lp trnh .Net c bin son nhm mc ch cung cp

nhng kin thc c bn v lp trnh trong mi trng .Net ca Microsoft.

Vi gio trnh ny sinh vin s c c cc kin thc v lp trnh to ra

cc dng ng dng khc nhau, bao gm: ng dng dng lnh (Console

Application), ng dng giao din windows (Windows Application) v ng

dng giao din web (ASP.NET Website Application).

V y l phin bn u tin nn gio trnh ny cn c nhng thiu st,

hn ch. Tc gi mong nhn c s gp qu bu t pha bn c. Mi

chi tit xin lin lc qua a ch email: minhlevan@cit.udn.vn

Xin chn thnh cm n.

i

Mc lc ii

MC LC

VISUAL STUDIO V .NET FRAMEWORK ..............................................1

I. Mc tiu ..................................................................................................................... 1

II. .NET Framework ................................................................................................... 1

II.1. Khi nim ...................................................................................................... 1

II.2. Kin trc ca .NET Framework..................................................................... 1

II.3. Cc ngn ng thuc h .NET ........................................................................ 2

II.4. Cc th vin c sn ca .Net Framework ...................................................... 2

III. Visual Studio ......................................................................................................... 3

III.1. Khi nim .................................................................................................. 3

III.2. Cch t chc chng trnh ca Visual Studio ........................................... 3

III.3. Cc dng Project ca Visual Studio .......................................................... 4

IV. Ngn ng lp trnh C# ........................................................................................... 4

IV.1. Khi nim .................................................................................................. 4

IV.2. c im .................................................................................................... 4

LP TRNH C# CN BN ............................................................................6

I. Mc tiu ..................................................................................................................... 6

II. Bt u vi Console Application ........................................................................... 6

II.1. To Project ..................................................................................................... 6

II.2. Lp trnh ........................................................................................................ 8

II.3. Bin dch ........................................................................................................ 8

II.3.1. Bin dch tng phn ................................................................................... 8

II.3.2. Bin dch ton phn ................................................................................... 9 II.4. Chy chng trnh ......................................................................................... 9

II.4.1. Ch debug ........................................................................................... 10

II.4.2. Ch non-debug .................................................................................... 10

III. Bin v phm vi hot ng ca bin trong C#..................................................... 11

III.1. Bin .......................................................................................................... 11

III.2. Phm vi hot ng ca bin ..................................................................... 11

IV. Hng..................................................................................................................... 12

V. Kiu d liu ......................................................................................................... 12

V.1. Kiu gi tr (Value Types) ........................................................................... 13

V.1.1. Kiu d liu s nguyn ............................................................................ 13 V.1.2. Kiu d liu du chm ng .................................................................... 13

V.1.3. Cc kiu d liu khc .............................................................................. 13

V.2. Kiu tham chiu (Reference Type) .............................................................. 13

VI. Cu trc iu kin ................................................................................................ 14

VI.1. Cu lnh iu kin if..else ....................................................................... 14

VI.1.1. C php ................................................................................................... 14

VI.1.2. Cch s dng ........................................................................................... 15 VI.2. Cu lnh switch..case............................................................................... 15

VI.2.1. C php ................................................................................................... 15

Mc lc iii

VI.2.2. Cch s dng ........................................................................................... 15

VII. Cu trc lp .......................................................................................................... 16

VII.1. Cu trc lp for ........................................................................................ 16

VII.1.1. C php ............................................................................................... 16

VII.1.2. Cch s dng ....................................................................................... 16

VII.2. Cu trc lp while .................................................................................... 17

VII.2.1. C php ............................................................................................... 17

VII.2.2. Cch s dng ....................................................................................... 17 VII.3. Cu trc lp do..while .............................................................................. 17

VII.3.1. C php ............................................................................................... 17

VII.3.2. Cch s dng ....................................................................................... 17 VII.4. Cc lnh h tr cho cu trc lp .............................................................. 18

VII.4.1. Lnh break ........................................................................................... 18

VII.4.2. Lnh continue ...................................................................................... 18

VIII. Mng (Array) ................................................................................................... 19

VIII.1. Mng mt chiu ....................................................................................... 19

VIII.1.1. C php khai bo ................................................................................. 19

VIII.1.2. Cch s dng ....................................................................................... 19

VIII.1.3. Cu trc lp foreach ............................................................................ 19

VIII.2. Mng hai chiu (Ma trn) ........................................................................ 20

VIII.2.1. C php khai bo ................................................................................. 20

VIII.2.2. Cch s dng ....................................................................................... 20

IX. X l nhp xut file ............................................................................................. 21

IX.1. Khi nim file .......................................................................................... 21

IX.2. Phn loi .................................................................................................. 21

IX.2.1. File vn bn (text file) ............................................................................. 21

IX.2.2. File nh phn (binary file) ....................................................................... 22

IX.3. c v ghi file vn bn ............................................................................ 22

IX.3.1. c file vn bn bng StreamReader ...................................................... 22

IX.3.2. Ghi file vn bn bng StreamWriter ........................................................ 24

LP TRNH HNG I TNG VI C# ........................................... 25

I. Mc tiu ................................................................................................................... 25

II. Lp (Class) .......................................................................................................... 25

III. i tng (Object) .............................................................................................. 27

IV. Thuc tnh (Attribute) .......................................................................................... 27

V. Phng thc (Method)......................................................................................... 27

VI. Np chng ton t (Overloading) ........................................................................ 28

VII. K tha (Inheritance) ........................................................................................... 29

VIII. a hnh (Polymorphism) ................................................................................. 31

IX. Interface ............................................................................................................... 33

X L BIT L ........................................................................................... 34

I. Mc tiu ................................................................................................................... 34

II. Bit l (Exception) ............................................................................................... 34

II.1. Chng trnh v li ...................................................................................... 34

Mc lc iv

II.2. Khi nim bit l ......................................................................................... 35

III. X l bit l (Exception Handler) ....................................................................... 35

III.1. C ch try/catch ....................................................................................... 35

III.2. X l bit l lng nhau ............................................................................ 37

III.3. X l bit l song song ............................................................................ 40

TH VIN LIN KT NG ................................................................... 42

I. Mc tiu ................................................................................................................... 42

II. Th vin trong lp trnh ....................................................................................... 42

II.1. Khi nim .................................................................................................... 42

II.2. Phn loi th vin ........................................................................................ 43

II.2.1. Th vin tnh ............................................................................................ 43

II.2.2. Th vin lin kt ng ............................................................................. 43

III. Namespace ........................................................................................................... 44

IV. Th vin lin kt ng ......................................................................................... 44

IV.1. Cch xy dng th vin vi Visual Studio 2005 ..................................... 44

IV.1.1. To mt project cho th vin ................................................................... 44

IV.1.2. Cu hnh cho project ............................................................................... 45

IV.1.3. Xy dng lp v phng thc cn thit .................................................. 46

IV.2. Cch s dng th vin ............................................................................. 47

IV.2.1. To thm tham chiu (add reference). ..................................................... 47

IV.2.2. Khai bo tham chiu ................................................................................ 48

IV.2.3. S dng th vin ...................................................................................... 49

V. Cc namespace c sn ca .Net Framework 2.0 .................................................. 49

V.1. Namespace System.Windows.Forms........................................................... 49

V.2. Namespace System.Data .............................................................................. 50

LP TRNH NG DNG WINDOWS ...................................................... 51

I. Mc tiu ................................................................................................................... 51

II. Cc bng iu khin ............................................................................................ 51

II.1. Toolbox panel .............................................................................................. 52

II.2. Solution Explorer panel ............................................................................... 53

II.3. Properties panel ........................................................................................... 54

III. Form v Label ...................................................................................................... 54

III.1. Form ........................................................................................................ 54

III.1.1. Khi nim Form ....................................................................................... 54

III.1.2. Cc thuc tnh ca Form ......................................................................... 54 III.1.3. Cc s kin ca Form .............................................................................. 55

III.2. Label ........................................................................................................ 56

III.2.1. Khi nim Label ...................................................................................... 56 III.2.2. Cc thuc tnh ca Label ......................................................................... 56 III.3. ng dng Form v Label ......................................................................... 56

III.3.1. To mi project ....................................................................................... 56 III.3.2. i tn Form chnh ................................................................................. 57

III.3.3. t tiu cho Form ............................................................................... 58 III.3.4. Ci t s kin FormClosed .................................................................... 59 III.3.5. Thm Label vo Form ............................................................................. 60

Mc lc v

III.3.6. Bin dch v chy ng dng .................................................................... 62

IV. TextBox v Button .............................................................................................. 62

IV.1. TextBox ................................................................................................... 62

IV.1.1. Khi nim TextBox .................................................................................. 62 IV.1.2. Cc thuc tnh ca TextBox ..................................................................... 62

IV.1.3. Cc s kin ca TextBox ......................................................................... 63 IV.2. Button ...................................................................................................... 63

IV.2.1. Khi nim Button ..................................................................................... 63 IV.2.2. Cc thuc tnh ca Button ....................................................................... 63 IV.2.3. Cc s kin ca Button ............................................................................ 64

IV.3. ng dng TextBox v Button ................................................................. 64

IV.3.1. To project, to Form v cc Label ........................................................ 64

IV.3.2. To cc TextBox ...................................................................................... 64

IV.3.3. Thm cc Button ...................................................................................... 65

IV.3.4. Ci t s kin cho tng Button .............................................................. 66

IV.3.5. Bin dch v chy chng trnh ............................................................... 67

V. ComboBox, CheckBox, RadioButton ................................................................. 67

V.1. ComboBox ................................................................................................... 67

V.1.1. Khi nim ComboBox .............................................................................. 67

V.1.2. Cc thuc tnh ca ComboBox ................................................................ 67

V.1.3. Cc phng thc ca ComboBox ............................................................ 68 V.1.4. Cc s kin ca ComboBox ..................................................................... 68

V.2. CheckBox .................................................................................................... 68

V.2.1. Khi nim CheckBox ............................................................................... 68

V.2.2. Cc thuc tnh ca CheckBox .................................................................. 69

V.2.3. Cc s kin ca CheckBox ...................................................................... 69

V.3. RadioButton ................................................................................................. 69

V.3.1. Khi nim RadioButton ........................................................................... 69

V.3.2. Cc thuc tnh ca RadioButton .............................................................. 69

V.3.3. Cc s kin ca RadioButton .................................................................. 69 V.4. ng dng ComboBox, CheckBox, RadioButton ........................................ 69

V.4.1. To project, to Form, to cc Label v TextBox ................................... 70

V.4.2. To cc RadioButton ............................................................................... 70 V.4.3. To ComboBox ........................................................................................ 71 V.4.4. To cc CheckBox ................................................................................... 72

V.4.5. To Button ............................................................................................... 73

V.4.6. Bin dch v chy chng trnh ............................................................... 73

VI. MDI Form v MenuStrip ..................................................................................... 74

VI.1. MDI Form ................................................................................................ 74

VI.1.1. Khi nim MDI Form .............................................................................. 74

VI.1.2. Cc thuc tnh ca MDI Form ................................................................ 75 VI.2. MenuStrip ................................................................................................ 75

VI.2.1. Khi nim MenuStrip ............................................................................... 75 VI.2.2. Cc thuc tnh ca MenuStrip ................................................................. 75 VI.3. ToolStripMenuItem ................................................................................. 75

VI.3.1. Khi nim ToolStripMenuItem ................................................................ 75

VI.3.2. Cc thuc tnh ca ToolStripMenuItem .................................................. 75

Mc lc vi

VI.3.3. Cc s kin ca ToolStripMenuItem ....................................................... 76

VI.4. ng dng MDI Form, MenuStrip ............................................................ 76

VI.4.1. To project v cu hnh MDI Form......................................................... 76

VI.4.2. To Form LogIn v Form Register ......................................................... 76 VI.4.3. To MenuStrip ......................................................................................... 77

VI.4.4. Vit s kin cho tng ToolStripMenuItem ............................................... 77

TNG TC C S D LIU ................................................................. 78

I. Mc tiu ................................................................................................................... 78

II. ADO.NET ............................................................................................................ 78

II.1. Khi nim .................................................................................................... 78

II.2. Kin trc ...................................................................................................... 78

II.3. Cc namespace phc v cho ADO.NET...................................................... 80

III. SqlConnection, SqlCommand ............................................................................. 80

III.1. SqlConnection ......................................................................................... 80

III.1.1. Khi nim SqlConnection ........................................................................ 80

III.1.2. Cc thuc tnh ca SqlConnection .......................................................... 80

III.1.3. Cc phng thc ca SqlConnection ...................................................... 81

III.2. SqlCommand ........................................................................................... 81

III.2.1. Khi nim SqlCommand .......................................................................... 81

III.2.2. Cc thuc tnh ca SqlCommand ............................................................ 81

III.2.3. Cc phng thc ca SqlCommand ........................................................ 82

III.3. ng dng SqlConnection, SqlCommand, ExcuteNonQuery .................. 82

III.3.1. To c s d liu ..................................................................................... 82

III.3.2. To bng tblUser ..................................................................................... 83

III.3.3. To stored procedure .............................................................................. 84

III.3.4. Lp trnh tng tc c s d liu ............................................................ 85

III.3.5. Bin dch v chy ng dng .................................................................... 86

IV. SqlDataReader v phng thc ExcuteReader.................................................... 87

IV.1. SqlDataReader ......................................................................................... 87

IV.1.1. Khi nim SqlDataReader ....................................................................... 87 IV.1.2. Cc thuc tnh ca SqlDataReader ......................................................... 87

IV.1.3. Cc phng thc ca SqlDataReader ..................................................... 87

IV.2. Phng thc ExcuteReader ..................................................................... 88

IV.3. ng dng SqlDataReader v phng thc ExcuteReader ...................... 88

V. SqlDataAdapter, DataSet v DataGridView........................................................ 89

V.1. SqlDataAdapter ........................................................................................... 89

V.2. DataSet ........................................................................................................ 89

V.3. DataGridView .............................................................................................. 90

V.3.1. Khi nim DataGridView ........................................................................ 90

V.3.2. Cc thuc tnh ca DataGridView .......................................................... 90 V.3.3. Cc s kin ca DataGridView ............................................................... 90

V.4. ng dng SqlDataAdapter, DataSet, DataGridView .................................. 90

V.4.1. To project ............................................................................................... 90

V.4.2. Thm i tng DataGridView ............................................................... 90 V.4.3. Ci t s kin Load ca Form ............................................................... 91 V.4.4. Bin dch v chy chng trnh ............................................................... 92

Mc lc vii

KT LUN .................................................................................................... 93

PH LC ........................................ ERROR! BOOKMARK NOT DEFINED.

Mc lc viii

L Vn Minh Trng Cao ng Cng ngh Thng tin, i hc Nng 1

Chng 1

Visual Studio v .NET Framework

I. Mc tiu

Trong chng ny, ngi hc s c cung cp mt s kin thc v cc vn sau:

1. Microsoft .Net Framework

2. Microsoft Visual Studio

3. Ngn ng lp trnh C#

II. .NET Framework

II.1. Khi nim

Microsoft .NET Framework l mt thnh phn c th c ci thm hoc c sn trong

cc h iu hnh Windows. N cung cp nhng gii php c lp trnh sn cho nhng

yu cu thng thng ca chng trnh qun l vic thc thi cc chng trnh vit trn

framework, ngi dng cui cn phi ci framework c th chy cc chng trnh c

pht trin bng cc ngn ng trong h .NET. .NET Framework do Microsoft a ra v c

s dng trong hu ht cc ng dng vit trn nn Windows. Nhng gii php c lp trnh

sn hnh thnh nn mt th vin cc lp ca framework, c s dng trong nhiu lnh vc

ca lp trnh nh: giao din ngi dng, truy cp d liu, kt ni c s d liu, m ho, pht

trin nhng ng dng website, cc gii thut s hc v giao tip mng. Th vin lp ca

framework c lp trnh vin s dng, kt hp vi chng trnh ca chnh mnh to nn

cc ng dng.

II.2. Kin trc ca .NET Framework

Microsoft t chc .NET Framework thnh nhiu tng, qu trnh bin dch v thc thi mt

chng trnh vit trn nn .NET Framework c thc hin tng bc t phn m ngun n

phn m my.

M ngun ca chng trnh sau khi bin dch s thnh ngn ng trung gian (Common

Intermediate Language - CIL). Ngn ng ny bin dch phn ln cc th vin c vit trn

nn .NET thnh cc th vin lin kt ng (Dynamic Linked Library - DLL). Vi gii php

ny, cc ngn ng c .NET Framework h tr s d dng s dng li ln nhau. Mt

chng trnh c vit bng ngn ng C# c th s dng cc lp, cc thuc tnh c vit

trc bng ngn ng VB.NET hoc J#.

Tng di cng ca cu trc phn tng ca .NET Framework l Common Language

Runtime cn c gi l CLR. y l thnh phn quan trng nht ca .NET Framework.

Tng ny thc hin bin dch m ca CIL thnh m my v thc thi.

Lp trnh .Net

2

Hnh 1 Cu trc ca .NET Framework

II.3. Cc ngn ng thuc h .Net

Hin ti cc lp trnh vin c th s dng nhiu ngn ng khc nhau lp trnh, c ngi

thn thin vi ngn ng ny, c ngi thn thin vi ngn ng khc. C ngi lm vic rt

tt vi ngn ng Basic, trong khi , mt s ngi khc thn thin vi ngn ng Java. Nhng

lp trnh vin vi kh nng thng tho nhng ngn ng khc nhau dng nh khng th cng

xy dng mt ng dng v s khng tng thch gia cc m lnh bin dch. khc phc

tnh trng ny, Microsoft a ra gii php .Net Framework. Vi .Net Framework, cc lp

trnh vin c th lp trnh nhng ngn ng khc nhau, sau khi bin dch, kt qu thu c s

l cc th vin lin kt ng .dll (dynamic linked library). Cc th vin ny s c cc lp

trnh vin khc k tha v s dng li.

Visual Studio v Microsoft .Net Framework h tr cc ngn ng lp trnh: Visual C++,

Visual Basic .NET, Visual C#, Visual J#. Cc ngn ng lp trnh trn c gi chung l h

ngn ng .NET.

II.4. Cc th vin c sn ca .Net Framework

Th vin lp c s ca .NET l mt tp hp ln cc lp c vit bi Microsoft, nhng

lp ny cho php bn thao tc rt nhiu cc tc v sn c trong Windows. Bn c th to cc

lp ca mnh t cc lp c sn trong th vin lp c s ca .NET da trn c ch tha k

n.

Th vin lp c s ca .NET rt trc quan v rt d s dng. V d, to mt tin trnh

mi, bn n gin gi phng thc Start() ca lp Thread. v hiu ha mt TextBox, bn

t thuc tnh Enabled ca i tng TextBox l false. Th vin ny c thit k d s

dng tng t vi cc ngn ng nh l Visual Basic v Java.

Lp trnh .Net

3

Cc th vin c sn .NET Framework bao gm:

Th vin h tr Windows GUI v Controls

Th vin Web Forms (ASP.NET)

Th vin Data Access (ADO.NET)

Th vin Directory Access

Th vin File system v Registry access

Th vin Networking v Web browsing

Th vin .NET attributes v reflection

Th vin h tr truy xut vo h iu hnh Windows

Th vin COM interoperability

III. Visual Studio

III.1. Khi nim

Visual Studio .Net l mi trng tch hp pht trin phn mm (Integrated Development

Environment (IDE)) ca Microsoft, l cng c cho php bn vit m, g ri v bin dch

chng trnh trong nhiu ngn ng lp trnh .NET khc nhau.

III.2. Cch t chc chng trnh ca Visual Studio

Chng trnh hoc ng dng hoc thm ch l mt h thng u c Visual Studio t

chc di dng Solution. Solution l tp hp ca nhiu Project. Project l tp hp cc tp tin

lin quan n mt ng dng v c ngi dng t chc theo cc cp th mc.

Mt Project ca Visual Studio thng thng bao gm 3 phn: phn thuc tnh (Properties),

phn tham chiu (References), phn ngi dng t nh ngha.

Hnh 2 Cu trc ca mt project ca Visual Studio

Lp trnh .Net

4

Phn thuc tnh (Properties) cha class AssemblyInfo trong m t cc thng tin c bn

v ng dng nh: tn ng dng, tn cng ty, a ch cng ty, bn quyn v cc thng tin khc.

Phn tham chiu (References) cha cc gi hoc cc class m ng dng ny cn dng.

Ngi dng c th s dng cc gi v cc class c sn ca .NET Framework hoc s dng

cc gi v class do ngi dng nh ngha. Cc gi v class ny c th c xy dng bng

nhiu ngn ng khc nhau min l cc ngn ng ny cng thuc h .NET.

Phn ngi dng nh ngha l phn cn li, ngi dng c th t nh ngha cc gi, cc

lp hoc thm vo mt s file d liu nu cn.

III.3. Cc dng Project ca Visual Studio

Hin nay, mt h thng thng tin thng c nhng dng ng dng sau: ng dng Console

phc v x l cc vn lin quan n h thng v giao tip vo ra; ng dng Desktop phc

v xy dng cc phn mm ng dng vi giao din thn thin; ng dng Internet phc v

vic xy dng cc website; i vi mi dng ng dng khc nhau, Visual Studio cung cp

cc dng Project khc nhau. Cc dng Project c Visual Studio cung cp gm c:

Console Application: Cung cp template cho ng dng Console

Windows Application: Cung cp template cho ng dng Desktop

Class Library: Cung cp template cho vic xy dng th vin lin kt ng

ASP.NET Website: Cung cp template cho vic xy dng Website

ASP.NET Web Service: Cung cp template cho vic xy dng Web Service

IV. Ngn ng lp trnh C#

IV.1. Khi nim

C# l mt ngn ng lp trnh hng i tng c pht trin bi Microsoft. Microsoft

pht trin C# da trn C++ v Java. C# c miu t l ngn ng c c s cn bng gia

C++, Visual Basic, Delphi v Java. C# c thit k ch yu bi Anders Hejlsberg kin trc

s phn mm ni ting vi cc sn phm Turbo Pascal, Delphi, J++, WFC.

IV.2. c im

C# l ngn ng lp trnh phn nh trc tip nht n .NET Framework m tt c cc

chng trnh .NET chy. C# ph thuc mnh m vo .Net Framework, mi d liu c s u

l i tng, c cp pht v hy b bi trnh dn rc Garbage-Collector (GC). C# cung cp

nhiu kiu tru tng khc chng hn nh class, delegate, interface, exception, v.v, phn nh

r rng nhng c trng ca .NET runtime.

So snh vi C v C++, ngn ng ny b gii hn v c nng cao mt vi c im no

, nhng khng bao gm cc gii hn sau y:

Lp trnh .Net

5

Cc con tr ch c th c s dng trong ch khng an ton. Hu ht cc i

tng c tham chiu an ton, v cc php tnh u c kim tra trn b m. Cc

con tr ch c s dng gi cc loi kiu gi tr; cn nhng i tng thuc b

thu rc (garbage-collector) th ch c gi bng cch tham chiu.

Cc i tng khng th c gii phng tng minh.

Ch c n k tha, nhng c th ci t nhiu interface tru tng (abstract

interfaces). Chc nng ny lm n gin ha s thc thi ca thi gian thc thi.

C# th an-ton-kiu (typesafe) hn C++.

C php khai bo mng khc nhau("int[] a = new int[5]" thay v "int a[5]").

L Vn Minh Trng Cao ng Cng ngh Thng tin, i hc Nng 6

Chng 2

LP TRNH C# CN BN

I. Mc tiu

Trong chng ny gio trnh s cung cp cho bn nhng kin thc c bn nht ca ngn

ng lp trnh C#. Nhng ch chnh nh sau:

Khai bo bin

Khi to v phm vi hot ng ca bin

Cch s dng cc vng lp v cu lnh

Cch s dng mng

Namespaces v th vin lin kt ng

C bn trnh bin dch dng lnh trong C#

S dng gi System.Console thc hin vic nhp xut

S dng ch thch trong C# v Visual Studio .NET

Cui chng ny ngi hc s c kh nng vit mt chng trnh gii quyt mt bi

ton n gin bng C#.

II. Bt u vi Console Application

Console Application l dng Project phc v vic lp trnh vi cc ng dng n gin. Vi

dng Project ny chng ta d dng thc hin vic lp trnh m phng thut ton v m

phng hng i tng. Cc bc khi to Console Application nh sau:

II.1. To Project

Ngay sau khi khi ng Visual Studio, chn Menu File New Project.

Lp trnh .Net

7

Hnh 3 Khi to Project

Sau khi chn vo Project, Visual Studio hin th giao din ngi dng chn dng

Project mc Project types v Templates, t tn cho Project mc Name v t ng dn

cho Project mc Location. v d hnh 4, ti liu trnh by cch to Project Console

Application vi tn l HelloWorld v Project ny c t trong th mc

E:\CDCNTT\GiaoTrinh\LapTrinh.Net - .NetProgramming.

Hnh 4 Cu hnh Console Application Project

Lp trnh .Net

8

II.2. Lp trnh

Ngay sau khi khi to, Visual Studio s to sn mt Project vi cu trc chun (Xem

chng 1, phn III.2). Trong Project, Visual Studio to sn mt class c tn l Program

nm trong file Program.cs, trong class ny c sn phng thc Main(), ngi s dng ch cn

lp trnh ngay ti phng thc ny.

Hnh 5 Lp trnh trong Console Application ca C#

Trong v d hnh 5, ti liu ny trnh by cch lp trnh hin th dng ch Hello

world. ra mn hnh. C# cung cp class Console thc hin vic xut hoc nhp d liu.

Dng lnh Console.Writeline(); dng hin th mt chui ra mn hnh. Dng lnh

Console.Readline(); dng nhp mt chui t bn phm.

Trong .NET Framework, Microsoft a ra thm khi nim namespace qun l cc class

trong cng mt th vin. Vi .NET, namespace l mt thut ng dng tham chiu v c

hiu l mt tp hp cc class. Nh th, mt th vin (*.dll) s l tp hp cha cc namespace

v trong mi namespace cha cc class. Visual Studio t to ra namespace mc nh trng

vi tn Project m bn t. Trong trng hp ny, namespace mc nh l HelloWorld.

II.3. Bin dch

Thng thng, mt ng dng hoc mt d n c t chc thnh mt Solution. Ty vo

mc ln nh, ta c 2 cch bin dch i vi ng dng m ta xy dng: bin dch tng phn

v bin dch ton b.

II.3.1. Bin dch tng phn

Bin dch tng phn l hnh thc bin dch tng Project trong mt Solution. Hnh thc

bin dch ny p dng i vi d n c chia thnh nhng thnh phn ring bit. Vi

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hnh thc bin dch, tc bin dch s nhanh v cc li d dng c phn vng sa

cha.

thc hin vic bin dch tng phn, ta c th click chut phi (right-click) vo Project

cn bin dch v chn Build.

Hnh 6 Bin dch tng phn

II.3.2. Bin dch ton phn

Bin dch ton b l hnh thc bin dch tt c cc Project trong mt Solution. Hnh thc

bin dch ny c p dng i vi cc ng dng va phi hoc cc ng dng m tt c cc

Project u c lin quan mt thit vi nhau. Vi hnh thc bin dch ny, tc bin dch s

chm, ty nhin tnh ng b c bo m.

thc hin bin dch ton phn, ta c th click phi chut (right-click) vo Solution ri

chn Build Solution.

Hnh 7 Bin dch ton phn

II.4. Chy chng trnh

Visual Studio cung cp 2 ch chy chng trnh: ch debug v ch non-debug.

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II.4.1. Ch debug

Ch debug l ch chy tng dng lnh ngi lp trnh bt li. Trong ch ny

ngi lp trnh quy nh mt s im dng gi l breakpoint, chng trnh s t ng dng

ti breakpoint ngi dng d dng theo di kt qu ca cc lnh chy tip theo. to ra

breakpoint, ngi lp trnh ch cn click phi chut (right-click) vo dng lnh cn dng ri

chn breakpoint ri chn Insert Breakpoint.

thc hin debug, ngi lp trnh c th bm F5 hoc chn vo Menu Debug Start Debug.

II.4.2. Ch non-debug

Ch non-debug l ch chy ht c chng trnh m khng dng li bt li cho d

ngi lp trnh thit lp breakpoint. chy ch ny, ngi lp trnh c th bm

Ctrl+F5 hoc chn vo Menu Debug Start Without Debugging.

Vi chng trnh HelloWorld trn kt qu chy chng trnh nh sau.

Hnh 8 Kt qu chy chng trnh

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III. Bin v phm vi hot ng ca bin trong C#

III.1. Bin

Bin l n v c cc ngn ng lp trnh t chc lu tr v x l d liu. Bin c

khai bo theo c php sau.

[modifier] datatype identifier;

[modifier] l mt trong nhng t kha public, private, protected, ; datatype l kiu d

liu; identifier l bin c ngi dng nh ngha;

V d di y mt bin mang tn i kiu s nguyn int v c th c truy cp bi bt c

hm no.

public int i;

Ta cng c th khai bo bin v khi to cho bin mt gi tr nh sau:

int i = 10;

Nu ta khai bo nhiu bin c cng kiu d liu s c dng nh sau:

int x = 10; y = 20;

III.2. Phm vi hot ng ca bin

Trong C#, phm vi hot ng ca bin l vng on m m t y bin c th c truy

xut. Thng thng mt on m c nh ngha bng mt cp du {}. Trong mt phm vi

hot ng (scope), khng th c hai bin cng mang mt tn trng nhau.

V d sau thc hin vic in ra cc s t 0 n 9 ra mn hnh ri tip tc in cc s t 9 n 0

ra mn hnh;

public static int Main()

{

for (int i = 0; i < 10; i++)

{

Console.WriteLine(i);

} // bin i ra khi phm vi

// Chng ta c th khai bo thm bin i y

for (int i = 9; i >= 0; i--)

{

Console.WriteLine(i);

} // bin i ra khi phm vi y

return 0;

}

Hnh 9 Minh ha phm vi ca bin

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Vi v d trn, trong 2 vng lp for khc nhau, ta c th khai bo cng mt bin i cho d 2

vng lp ny cng nm trong mt khi lnh. iu ny hp l bi v i c khai bo trong hai

vng lp khc nhau v l bin cc b ca 2 vng lp . Khi vng lp hon c thc hin

xong th bin t ng c gii phng v v th cc bin cc vng lp khc nhau th c th

c t tn ging nhau.

IV. Hng

Mt hng (constant) l mt bin nhng tr khng th thay i c sut thi gian thi hnh

chng trnh. i lc ta cng cn c nhng gi tr bao gi cng bt bin.

Hng c khai bo nh sau:

const datatype identifier = value;

V d: const int numberOfModules = 12;

Hng c nhng c im sau:

Hng bt buc phi c gn gi tr lc khai bo. Mt khi c khi gn th khng

th vit ln

Tr ca hng phi c th c tnh ton vo lc bin dch, do khng th gn mt

hng t mt tr ca mt bin.

Hng bao gi cng static, tuy nhin ta khng th a t kho static vo khi khai bo

hng

C ba thun li khi s dng hng trong chng trnh ca bn:

Hng lm cho chng trnh c d dng hn, bng cch thay th nhng con s v cm

bi nhng tn mang y ngha hn

Hng lm cho d sa chng trnh hn, vic thay i gi tr ch cn thc hin mt ln

ngay ti v tr khai bo hm

Hng lm cho vic trnh li d dng hn, nu bn gn mt tr khc cho mt hng vn

c khai bo u trong chng trnh trnh bin dch s t ng thng bo li v

hng ny c khai bo

V. Kiu d liu

C# l mt ngn ng c kim sot cht ch v mt kiu d liu, ngoi ra C# cn chia cc

kiu d liu thnh hai loi khc nhau: kiu tr (value type) v kiu qui chiu (reference type).

Ngha l trn mt chng trnh C# d liu c lu tr mt hoc hai ni tu theo c th ca

kiu d liu.

C# cng h tr kiu con tr (pointer type) ging nh C++ nhng t khi dng n v ch

dng khi lm vic vi on m unmanaged. on m unmanaged l on m uc to ra

ngoi .NET Framework, chng hn nhng i tng COM.

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V.1. Kiu gi tr (Value Types)

V.1.1. Kiu d liu s nguyn

Tn kiu Din gii Min gi tr

sbyte S nguyn c du 8bit -128:127

short S nguyn c du 16bit -215

:215

-1

int S nguyn c du 32bit -231

:231

-1

long S nguyn c du 64bit -263

:263

-1

byte S nguyn khng du 8bit 0:255

ushort S nguyn khng du 16bit 0:216

-1

uint S nguyn khng du 32bit 0:232

-1

ulong S nguyn khng du 64bit 0:264

-1

Hnh 10 Danh sch cc kiu s nguyn ca C#

Vi cc kiu d liu trn, ta c th khai bo bin nh sau:

long x = 0x12ab; // ghi theo hexa

int i = 1234;

Khi s dng cc kiu s nguyn ca C# cn ch rng kiu int ca C# c cp pht 32bit

khng ging nh kiu int ca Ansi C vn ch c cp pht 16bit. Ni mt cch khc kiu int

trong C# tng ng vi kiu long trong Ansi C.

V.1.2. Kiu d liu du chm ng

Tn kiu Din gii S ch s c ngha

float Kiu s thc 32bit 7

double Kiu s thc 64bit 16

Hnh 11 Danh sch cc kiu d liu du chm ng

V.1.3. Cc kiu d liu khc

Tn kiu Din gii Ghi ch

decimal S thp phn 128bit 28 ch s c ngha

bool Kiu logic [true, false]

char Kiu k t 16bit kiu k t unicode

Hnh 12 Cc kiu d liu khc

V.2. Kiu tham chiu (Reference Type)

C# h tr 2 kiu tham chiu c bn: object, string. Kiu object l kiu d liu d liu gc,

tt c cc kiu d liu khc u c dn xut t kiu d liu ny. Kiu string l kiu d liu

trnh by chui k t. Chui string trong C# h tr hon ton unicode.

Cng ging nh Ansi C v Java, C# nh ngha gi tr ca mt chui trong cp du ngoc

kp , cn c gi l Double Quote. tin cho vic x l tt c cc k t, C# nh ngha

mt s k t c bit gi l Escape Sequence.

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Danh sch cc Escape Sequence thng dng.

Escape Sequence Din gii

\' Single quote

\" Double quote

\0 Null

\n Return

\\ Backslash

Hnh 13 Danh sch Escape Sequence

C# h tr ton t + ghp ni cc chui v ton t = gn gi tr cho chui. V d sau

trnh by cc ton t dng cho kiu string.

public static int Main()

{

string s1 = "Windows folder is: ";

string s2 = "C:\\windows";

Console.WriteLine("s1 is: " + s1);

Console.WriteLine("s2 is: " + s2);

s1 = s1 + s2;

Console.WriteLine("s1 is now: " + s1);

Console.WriteLine("s2 is now: " + s2);

return 0;

}

Hnh 14 Minh ha cc ton t trn kiu string

Chng trnh chy ra kt qu nh sau:

s1 is: Windows folder is

s2 is: C:\windows

s1 is now: Windows folder is C:\windows

s2 is now: C:\windows

Hnh 15 Kt qu chy chng trnh v d trong hnh 14

Vi v d trn, cho thy sau khi thc hin ton t gn th gi tr ca biu thc bn phi s

c gn vo bin bn tri cho d biu thc pha bn phi c s xut hin ca bin c tr

v. Cng trong v d ny, m t k t \ (k t ng dn hay k t Backslash), chng ta

phi s dng quy nh ca Escape Sequence, trong trng hp ny, v d s dng k t \\.

VI. Cu trc iu kin

VI.1. Cu lnh iu kin if..else

VI.1.1. C php

if (condition) statement(s);

[else statement(s);]

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VI.1.2. Cch s dng

Lnh iu kin if thc hin mt hoc nhiu lnh trong khi lnh nu kt qu tr v ca

biu thc condition l true, ngc li, cc lnh hoc khi lnh ngay sau t kha else s c

thc hin. Xt v d sau:

if (i != 0)

{

Console.WriteLine(i is not Zero);

}

else

{

Console.WriteLine(i is Zero);

}

Hnh 16 Minh ha cu trc if..else

V d trn thc hin vic kim tra bin i c bng 0 hay khng. Nu i bng 0, chng trnh

s xut ra i is Zero, ngc li, chng trnh s xut ra i is not Zero.

VI.2. Cu lnh switch..case

Trong trng hp phi dng nhiu lnh if..else lng nhau, chng trnh s tr nn phc tp

v kh g ri. khc phc vn ny, C# cung cp cu trc lnh switch..case phc v

cho vic lp trnh khi x l mt lot cc trng hp khc nhau ca cng mt iu kin.

VI.2.1. C php

switch (expression)

{

case (condition): statement(s);

[break;]

case (condition): statement(s);

[break;]

[default: statement(s);]

}

VI.2.2. Cch s dng

Vi tng trng hp ca biu thc iu kin expression, cc lnh tng ng s c thc

hin. Trong cu trc lnh ny, lnh break c s dng nhy ra khi khi lnh. Ch dn

default c s dng gii quyt trng hp ca iu kin m trng hp ny khng nm

trong tt c cc trng hp lit k trong cc ch dn case. V d sau trnh by cch s dng

lnh switch..case vo vic tnh s ngy trong mt thng c nhp t bn phm.

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Hnh 17 Minh ha cu trc switch..case

VII. Cu trc lp

VII.1. Cu trc lp for

VII.1.1. C php

for (initializer; condition; iterator)

statement(s)

VII.1.2. Cch s dng

Cu trc ca lnh for bao gm biu thc khi to initializer, iu kin kt thc condition,

biu thc bin i iterator. Lnh for thc hin vic lp mt hoc nhiu lnh trong khi iu

kin kt thc condition vn cn ng. V d sau minh ha cho chng trnh xut ra mn hnh

tt c cc s dng chia ht cho 3 m nh hn 100.

Hnh 18 Minh ha cu trc lp for

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VII.2. Cu trc lp while

VII.2.1. C php

while(condition)

statement(s);

VII.2.2. Cch s dng

Cu trc while thc hin vic lp mt hay nhiu lnh khi iu kin condition vn cn

ng. Khi s dng cu trc ny, ngi lp trnh cn phi ch ng thc hin cc cu lnh to

s bin i trnh nhng vng lp v tn. V d sau minh ha cho chng trnh tnh c

chung ln nht ca 2 s nguyn a, b.

Hnh 19 Minh ha cu trc lp while

VII.3. Cu trc lp do..while

VII.3.1. C php

do

{

statement(s);

} while (condition);

VII.3.2. Cch s dng

Cu trc lp do..while thc hin vic lp mt hoc nhiu lnh cho ti khi iu kin

condition c gi tr false. Cu trc lp ny c c im l cc lnh c thc hin t nht mt

ln cho d ngay t u iu kin l false. V d sau y minh ha cho chng trnh tnh

tng cc s dng b hn 100.

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Hnh 20 Minh ha cu trc lp do..while

VII.4. Cc lnh h tr cho cu trc lp

VII.4.1. Lnh break

Lnh break thc hin vic dng vng lp. Khi chng trnh ang chy m gp lnh break

th chng trnh s lp tc chm dt vng lp cho d iu kin ca vng lp vn cho php

chy tip. Trong trng hp c nhiu vng lp lng nhau, chng trnh s chm dt vng lp

gn vi break nht. V d sau s dng vng lp for v cu lnh break tnh tng tt c cc

s nguyn t nh hn 100.

Hnh 21 Minh ha lnh break

VII.4.2. Lnh continue

Trong khi thc hin vng lp, ngi lp trnh i khi cn thc hin vic b qua mt s

dng lnh tip tc thc hin vic lp cho ln tip theo. C# h tr lnh continue thc

hin chc nng ny. Lnh continue thc hin vic chuyn sang ln lp tip theo v b qua cc

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lnh nm trong vng lp nhng nm pha sau n. V d sau minh ha cho vic s dng vng

lp for v lnh continue.

Hnh 22 Minh ha lnh Continue

VIII. Mng (Array)

Mng hay cn gi l Array l mt cu trc d liu cu to bi mt s bin c gi l

nhng phn t mng. Tt c cc phn t ny u thuc mt kiu d liu. Ngi lp trnh c

th truy xut phn t thng qua ch s (index). Ch s bt u bng zero.

Ngi ta thng chia mng thnh 2 loi: Mng mt chiu v mng nhiu chiu. i vi

mng nhiu chiu gio trnh ny ch trnh by mng hai chiu bi v mng hai chiu l c

trng tiu biu cho mng nhiu chiu.

VIII.1. Mng mt chiu

VIII.1.1. C php khai bo

type[ ] array-name;

hoc type[] array-name = new type[length];

Vi c php trn, type l kiu d liu ca cc phn t trong mng, array-name l tn ca

mng, length l di ca mng di ny chnh l s phn t ca mng.

VIII.1.2. Cch s dng

lm vic vi mng, ngi lp trnh thng can thip trc tip vo tng phn t ca

mng thng qua ch s index vi c php array-name[index]. V d:

x = A[0];

st = B[i];

B[1] = x;

duyt mng, ngi lp trnh thng s dng cu trc lp. Bn cnh cc cu trc lp

trnh by, C# cn cung cp mt cu trc lp khc l vng lp foreach.

VIII.1.3. Cu trc lp foreach

Cu trc lp foreach c thc hin theo cu trc sau:

foreach (data-type identifier in array-name) statement(s)

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Vi mi gi tr ca mng array-name, chng trnh s thc hin mt hoc nhiu lnh

statement(s). Trong , gi tr ca mi phn t c tham chiu qua bin identifier m bin

ny thuc kiu data-type. V d sau minh ha vic s dng mng mt chiu v minh ha cho

phng php duyt mng mt chiu bng cu trc lp foreach.

Hnh 23 Minh ha cu trc foreach khi duyt mng Array

VIII.2. Mng hai chiu (Ma trn)

VIII.2.1. C php khai bo

type[,] array-name;

hoc type[,] array-name = new type[height, width];

Vi c php trn, type l kiu d liu ca cc phn t trong mng, array-name l tn ca

mng, height v width ln lt l s dng v s ct ca ma trn. V d nh sau:

int[,] myRectArray = new int[2,3]; //khai bo mng s nguyn c 2 dng v 3 ct

int[,] myRectArray = new int[,]{ {1,2},{3,4},{5,6},{7,8}}; //khai bo mng 4 hng 2 ct

string[,] beatleName = { {"Lennon","John"}, {"McCartney","Paul"},

{"Harrison","George"}, {"Starkey","Richard"} }; //khai bo mng string c 2 dng 4 ct

VIII.2.2. Cch s dng

lm vic vi mng hai chiu, ngi lp trnh c th can thip trc tip vo tng phn t

ca mng thng qua ch s hng v ch s ct. V d nh sau:

A[0, 1] = 2; //Gn gi tr 2 vo phn t hng 0 ct 1

Console.Write(A[2, 3]); // Ghi gi tr ca phn t hng 2 ct 3 ra mn hnh

V cu trc lu tr ca ma trn bao gm cc hng v cc ct nn ngi lp trnh thng s

dng hai vng lp lng nhau thc hin vic duyt c ma trn. V d sau minh ha vic

duyt ma trn bng cch s dng hai vng lp lng nhau, trong qu trnh lp, chng trnh s

hin th cc chui trong ma trn.

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Hnh 24 Minh ha vic s dng hai vng lp lng nhau khi dng ma trn

IX. X l nhp xut file

IX.1. Khi nim file

File cn c gi l tp tin hoc c gi l tp l khi nim dng ch tp hp nhng

thng tin lin quan vi nhau v nhng thng tin ny c lu tr trn a.

Khc vi nhng thng tin c lu tr trn RAM, cc thng tin c lu trong file phi

c truy cp mt cch tun t, ngha l mun c hoc ghi d liu v tr th i th b x l

phi thc hin vic c hoc ghi t v tr 0 n v tr i-1.

IX.2. Phn loi

Ty vo ni dung d liu cha trong file, file c chia thnh 2 loi: file nh phn (binary

file) v file vn bn (text file). Trong phn ny gio trnh ch trnh by phng php c ghi

i vi file vn bn, ngi hc t nghin cu phng php c ghi file nh phn t cc ti

liu tham kho trong phn ti liu tham kho cui gio trnh.

IX.2.1. File vn bn (text file)

File vn bn l file m d liu ghi trong l nhng k t thuc bng m ASCII chun

(bng m khng bao gm cc k t iu khin) trong cc k t c t chc thnh nhiu

hng. Cc hng c phn cch bng k t xung hng.

i vi cc file vn bn c t chc trn h iu hnh Dos hoc Windows ca Microsoft

th cc hng c phn cch bi mt cp k t bao gm: k t xung dng v k t v u

dng. i vi cc file vn bn c t chc trn h iu hnh Unix hoc Linux th cc hng

c phn cch bi mt du xung hng. iu ny gii thch ti sao khi ngi s dng m

mt s file vn c son tho trong h iu hnh Linux bng chng trnh son tho ca

Windows (c th l notepad) th tt c cc dng ca file c ni thnh mt dng duy nht.

Cc file vn bn thng thng l nhng file vn bn n gin hoc nhng file m ngun

ca nhng ngn ng lp trnh hoc nhng file c s d liu XML.

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IX.2.2. File nh phn (binary file)

File nh phn l file m thng tin lu tr mt cch tng qut. D liu lu tr trn file nh

phn c chia thnh tng byte, mi byte c c trng bi mt k t ca bng m ASCII

m rng.

Cc file nh phn thng c mt cu trc hoc nh dng ring, nhng file c bin son

theo nh dng no th ch c nhng phn mm hiu c nh dng mi c th c c.

V d nhng file hnh ng th ch c th c c bng nhng chng trnh hin th hnh nh.

Cc chng trnh son tho cho file vn bn th khng hin th chnh xc file nh phn. C

th l khi ngi s dng dng chng trnh son tho vn bn m mt file thc thi (.exe)

th chng trnh son tho vn bn y ch hin th cc k t c bit.

Cc file nh phn thng thng l nhng file thc thi (.exe), file hnh nh (.jpg, .gif, ..png,

.bmp, ), file m thanh (.mp3, .wma, .mid, .wav, ), file cha cc on phim (.mpg, .wmv,

.rm, ) v nhiu dng nh dng mc nh khc.

IX.3. c v ghi file vn bn

Visual Studio cung cp nhiu i tng thc hin vic c v ghi file vn bn. Gio

trnh ny trnh by vic c bng cp i tng StreamReader v StreamWriter. y l cp

i tng c/ghi tng qut, ngi lp trnh c th s dng cp i tng ny thc hin

vic c hoc ghi trn cc lung nhp xut khc. s dng phng thc ny, ngi lp

trnh phi khai bo s dng namespace System.IO ca Visual Studio bng lnh using

System.IO chi tit v namespace s c trnh by trong chng tip theo. Ngi hc t

nghin cu cc phng php c ghi file khc t cc gio trnh c nu trong phn ti liu

tham kho.

IX.3.1. c file vn bn bng StreamReader

StreamReader l mt lp v lp ny thc to ra cc i tng phc v vic c d liu t

mt lung hoc mt file. Khi khi to i tng, ngi lp trnh phi cung cp tn file cho

phng thc khi to. Vic khi to i tng c th sinh ra cc li nh file khng tn ti,

a b hng, , do , hm khi to phi c t trong khi try/catch x l bit l X

l bit l s c trnh by chng tip theo.

i tng StreamReader cung cp nhiu phng php c d liu, trong phng

thc hu hiu nht l phng thc ReadLine(). Phng thc ReadLine() thc hin vic c

tng dng trong file vn bn v tr v mt chui string. V d sau trnh by vic c d liu

t file vn bn c tn l input.txt, file ny cha cc s nguyn, mi s nguyn nm trn mt

dng.

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Hnh 25 File input.txt

Chng trnh sau s dng i tng StreamReader c file input.txt v tnh tng cc s

nguyn ca trong file .

Hnh 26 Chng trnh s dng StreamReader c file vn bn

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IX.3.2. Ghi file vn bn bng StreamWriter

Cng ging StreamReader, StreamWriter l mt lp v lp ny to ra cc i tng phc

v vic ghi d liu vo mt lung hoc mt file. Khi khi to i tng, ngi lp trnh phi

cung cp tn file cho phng thc khi to. Vic khi to i tng c th sinh ra cc li nh

a b hng hoc li nhp xut, , do , hm khi to phi c t trong khi try/catch

x l bit l X l bit l s c trnh by chng tip theo.

i tng StreamWriter cung cp nhiu phng php ghi d liu, trong phng

thc hu hiu nht l phng thc Write(). Phng thc Write() thc hin vic ghi mt chui

string vo file vn bn. V d sau trnh by vic ghi d liu t file vn bn c tn l output.txt.

Hnh 27 Chng trnh s dng StreamWriter ghi file vn bn

Sau khi chy chng trnh, file vn bn thu c nh sau.

Hnh 28 File kt qu thu c sau khi chy chng trnh

L Vn Minh Trng Cao ng Cng ngh Thng tin, i hc Nng 25

Chng 3

LP TRNH HNG I TNG VI C#

I. Mc tiu

T cc hc phn Lp trnh hng i tng vi C++ v Lp trnh Java, ngi hc c tip cn l thuyt v thc hnh vi Lp trnh hng i tng (Object Oriented Programming). Trong chng ny gio trnh cng cung cp nhng kin thc c bn v lp

trnh hng i tng tuy nhin cc nguyn l ny c vn hnh bng ngn ng C#. Nhng

ch chnh c trnh by trong chng ny nh sau:

Lp (Class) v i tng (Object)

Thuc tnh (Attribute) v Phng thc (Method)

Np chng ton t (Overloading)

K tha (Inheritance)

a hnh (Polymorphism)

Interface

Cui chng ny ngi hc s c kin thc gii quyt cc vn lp trnh bng

quan im hng i tng.

II. Lp (Class)

Lp l mt khi nim trong phng php lp trnh hng i tng (Object Oriented

Programming) c dng ch s gi gn cc d liu v cc phng thc hot ng trn d

liu . Lp cn c hiu l khi nim dng ch tp hp tt c cc thc th c chung mt

s thuc tnh no trong phm vi ng cnh no . V d, khi xt mt s thc th gm bo,

h, s t, nga vn; Nu cc thc th ny c xt trong ng cnh ch ch n 3 yu t gm

mu lng, cn nng, tc di chuyn th cc thc th ny c th c gp chung vo mt lp

gi l lp Th;

Trong C#, tt c cc lp c dn xut t lp c s System.Object. Mi lp thng c

nh ngha trong mt file .cs v file ny c thm vo project. V d sau y minh ho vic

xy dng mt class. Trong class ny ch c mt thuc tnh l name v mt phng thc l

Speak(). Cng ging nh cc ngn ng C++ v Java, C# cung cp con tr this dng tham

chiu n mt th hin (instance) ca class ang xt.

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Hnh 29 Minh ho vic xy dng Class trong C#

Trong lp c mt phng thc mc nh dng khi to i tng c gi l phng

thc khi to (constructor). Phng thc khi to c c t tn trng vi tn lp v c

ch dn truy cp bt buc l public phng thc ny c th c triu gi t bn ngoi

phng thc. Cc ch dn bin dch (accessibility) bao gm: public, internal, protected,

private c m t chi tit theo hnh sau.

Ch dn truy cp M t

public Bin v phng thc c th c truy cp t bt k

ni u (bn ngoi cng nh bn trong lp)

internal Bin v phng thc ch c th c truy cp trong

cng mt gi

protected Bin v phng thc ch c truy cp ngay trong

lp hoc c c truy cp t trong lp k tha

ca n

private Bin v phng thc ch c truy cp ngay trong

phm vi ca lp

Hnh 30 M t cc ch dn truy cp trong C#

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27

III. i tng (Object)

i tng l khi nim dng ch mt trng hp c th (instance) ca mt lp. Trong

lp trnh hng, i tng l thc th c bn ca vic lp trnh, cc ng x v hnh vi ca i

tng c chng trnh triu gi thng qua cc phng thc c m t lp thuc i

tng . Cng ging nh cc lp trong C#, tt c cc i tng cng c k tha t i

tng c s System.Object. V d sau minh ha vic khai bo v s dng i tng ca lp

Dog va c m t trn.

Hnh 31 Minh ha vic khai bo v s dng i tng

Trong v d trn, ton t new c s dng khi khi to i tng. Tham s ban u ca

phng thc khi to c a vo trc tip t tham s ca ton t new. Phng thc c ch

dn truy cp l public c triu gi bng cch gi tn i tng v tn phng thc, trong

du chm (dot) c s dng ngn cch gia i tng v phng thc cn triu gi.

IV. Thuc tnh (Attribute)

Thuc tnh l khi nim dng ch cc tnh cht c trng ca mt lp. Trong mt lp,

cc thuc tnh c m t mt cch nh tnh bao gm tn thuc tnh, kiu d liu v ch dn

truy cp. Trong mt i tng, cc thuc tnh c th hin mt cch nh lng vi vic cc

thuc tnh c cung cp mt gi tr xc nh (gi tr mc nh l null nu nh thuc tnh

cha cung cp gi tr)

C# cung cp th tc get v set thc hin vic truy cp mt thuc tnh, th tc get ly

gi tr v th tc set thc hin vic thay i gi tr. V d hnh 25 m t th tc get v set

i vi thuc tnh private string _name, th tc get v set thc hin vic nh ngha mt nh

danh (alias) khc c tn l Name ngi dng s dng khi truy cp vo thuc tnh _name.

Nu khng c th tc ny, ngi s dng khng th truy cp thuc tnh _name v thuc tnh

ny c nh ngha vi ch dn truy cp l private.

V. Phng thc (Method)

Phng thc l khi nim dng ch mt ng x hoc l mt hnh ng ca i tng.

Trong C#, phng thc c chia thnh 2 loi: non-static method v static method.

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Non-static method l phng thc ch c th c gi t i tng, phng thc ny

mang tnh c th ca i tng v nhng i tng khc nhau trong cng mt lp s

c nhng kt qu tr v khng ging nhau khi cng triu gi mt phng thc thuc

loi ny. Trong v d hnh 27, phng thc Speak() do i tng toto thc hin s

c kt qu khc vi phng thc do i tng milu triu gi.

Static method l phng thc c trng cho tt c cc i tng thuc lp . Phng

thc ny khng th c gi t i tng m phi c gi trc tip t lp. Kt qu

chy phng thc ny khng ph thuc vo i tng m ph thuc vo tham s u

vo ca phng thc. Trong cc v d trn, phng thc Console.Writeln() l phng

thc static ca lp Console.

VI. Np chng ton t (Overloading)

Np chng ton t l khi nim dng ch vic nh ngha li mt s ton t m nhng

ton t ny lm vic vi d liu l i tng thuc lp m ngi lp trnh ang xy dng.

Ton t c tnh ng nht i vi tt c cc i tng thuc lp hoc i vi tt c cc gi tr

thuc kiu d liu do C# yu cu tt c cc ton t phi l static method vi ch dn truy

cp l public. Trong C#, tt c cc lp u dn xut t lp c s System.Object v lp ny

vn nh ngha sn phng thc equal v ton t gn (=) do ngi lp trnh khng cn

thit phi nh ngha li ton t gn. V d sau y trnh by vic np chng ton t cng (+)

i vi i tng thuc lp phn s (Fraction).

Hnh 32 Minh ha vic np chng ton t

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V d trn trnh by vic np chng ton t cng (+) 2 phn s (Fraction). Ton t ny

c khai bo vi tin t static operator v ch dn truy cp l public.

VII. K tha (Inheritance)

K tha l khi nim then cht ca cc ngn ng lp trnh hng i tng dng hiu

hin tng mt lp thc hin vic s dng li mt s thuc tnh (attribute) hoc phng thc

(method) ca mt lp khc. Lp s dng cc thuc tnh v phng thc ca lp khc c

gi l lp dn xut, i khi cn c gi l lp con. Lp cho php lp khc s dng cc

thuc tnh v phng thc c gi l lp c s, i khi cn c gi l lp cha.

K tha trong hng i tng c chia thnh hai loi: n k tha (single inheritance)

v a k tha (multiple inheritance). n k tha c hiu l mt lp dn xut s dng cc

thuc tnh v phng thc ca mt lp c s duy nht. Ngc li, nu mt lp s dng cc

thuc tnh v phng thc t nhiu lp s s th c gi l a k tha.

C++ h tr c n k tha v a k tha, tuy nhin C# ch h tr n k tha. Vic s

dng a k tha mt cch hp l s gip cho chng trnh ti u hn v mt kch thc

nhng vic x l li (nu c) s v cng phc tp. y l l do c bn m C# ch thit k cho

n k tha. V d sau trnh by vic xy dng mt lp c s v hai lp k tha.

Hnh 33 Lp c s

V d trn trnh by vic xy dng lp c s Dog gm hai thuc tnh l Name, Weight v

hai phng thc l Speak(), DrinkWater().

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Hnh 34 Cc lp dn xut

V d trn trnh by hai lp dn xut t lp c s l Dog. Lp th nht l GermanShepard

trong c thm phng thc l OnGuard(), lp cn li l JackRussell c thm phng thc

l Chew(); V d sau s minh ha vic s dng hai lp dn xut dn xut trn.

Hnh 35 Minh ho vic s dng lp dn xut

V d trn khai bo hai i tng: i tng Simon thuc lp GermanShepard v i

tng Daisy thuc lp JackRussell. Khi gi phng thc Speak() v DrinkWater() t lp c

s th cc ng x (hoc kt qu thu c) ca chng trnh l ging nhau. Tuy nhin khi gi

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phng thc c th t lp dn xut phng thc OnGuard() i vi Simon v phng thc

Chew() i vi Daisy th kt qu thu c khc nhau.

Trong mt ng dng, vic tn dng tnh nng k tha ca hng i tng lm cho

chng trnh tr nn ngn gn, d hiu. Trong tnh hung chng trnh c cha rt nhiu lp

tng t nhau trong c rt nhiu phng thc ging nhau th vic xy dng mt lp c s

trong c nhiu phng thc chung lm cho vic cp nht chnh sa c thun li, v

ngi lp trnh ch cn sa mt ln ti lp c s thay v phi chnh sa tng phng thc

trong tng lp.

VIII. a hnh (Polymorphism)

a hnh l thut ng c dng trong hng i tng dng ch vic ng x khc nhau

ca cc i tng trong nhng lp k tha t mt lp c s khi mt phng thc chung c

gi. Tnh a hnh c s dng trong trng hp mt phng thc chung c s dng trong

nhiu lp dn xut nhng ng vi mi lp dn xut c th th phng thc ny c nhng ng

x khc nhau.

thc hin c tnh a hnh, phng thc lp c s phi c m t dng o

(virtual) v phng thc lp dn xut phi c ghi (override). Override l thut ng

c dng ch vic lp dn xut c t li phng thc lp c s. V d sau trnh by

vic thc hin tnh nng a hnh khi xy dng mt lp c s v hai lp dn xut.

Hnh 36 Lp c s v phng thc virtual khi thc hin tnh a hnh

Hnh trn minh ha cho lp c s trong c mt phng thc o (virtual). Phng thc

ny s c ghi (override) lp c s. Cc hnh tip theo trnh by vic xy dng hai lp

dn xut trong mi lp, phng thc Speak() c nh ngha li bng cch ghi (override).

Nu ngi lp trnh khng s dng t kha override th Visual Studio vn khng bo li. Tuy

nhin, phng thc Speak() trong lp dn xut c hiu l phng thc ring ca chnh lp

dn xut v phng thc ny ch c gi trc tip t lp dn xut.

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Hnh 37 Lp dn xut th nht c phng thc override

Hnh 38 Lp dn xut th hai c phng thc override

minh ha cho kh nng ng x ca nhng i tng thuc nhng lp khc nhau khi

chng u triu gi mt phng thc ta xy dng mt mng gm 3 i tng trong i

tng th nht thuc lp c s, hai i tng cn li thuc lp dn xut. Khi gi phng

thc Speak() cho tng i tng, chng trnh s cho ra cc kt qu khc nhau do tnh nng

Polymorphism.

Hnh 39 Minh ha vic s dng Polymorphism

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Trong hnh trn, mi phn t ca mt mng c gn nhng i tng khc nhau. V cc

i tng u thuc mt lp c s hoc thuc lp dn xut t chnh lp c s nn vic

gn nhng i tng nh th vo cng mt mng khng gy ra xung t.. Cng trong v d

trn, khi thc hin mt vng lp duyt qua tt c cc i tng m trong , ng vi mi i

tng, phng thc Speak() c th s c gi v kt qu thu c s khc nhau qua tng

phng thc.

IX. Interface

Interface c mt tc gi khc dch thnh cc thut ng l giao din hoc giao tip.

Thut ng Interface c dng ch mt lp tru tng. Lp tru tng ny c xy dng

nhm thun tin ha vic pht trin chng trnh theo phong cch xy dng thnh phn c s

(component-based). Interface cung cp nhng tha thun chung cho php cc thnh phn c

th lm vic vi nhau. Interface c s dng rt c lc trong vic x l cc s kin (Event

Handler) khi xy dng cc i tng giao din ngi dng (GUI Graphic User Interface).

Ngi hc c th tham kho m hnh x l s kin ActionPerformce khi x l Button trong

hc phn Java hc trc .

Interface khng phi l mt lp hon chnh nn c bt c m ci t no v khng th

c dng khi to i tng. Interface ch c cc thuc tnh, cc phng thc (phng

thc ny ch c tn khai bo m khng c m ci t). Tt c cc thuc tnh, phng thc

phi c khi bo vi ch dn truy cp l public.

Khi mt lp thc hin vic k tha t mt hoc nhiu Interface th trong lp , tt c cc

phng thc thuc cc Interface u phi c nh ngha hon chnh.

L Vn Minh Trng Cao ng Cng ngh Thng tin, i hc Nng 34

CHNG 4

X L BIT L

I. Mc tiu

Trong chng ny gio trnh s trnh by qu trnh nm bt v x l li khi lp trnh C#.

Nhng ch chnh c trnh by trong chng ny nh sau:

Bit l (Exception)

X l bit l (Exception Handler)

X l nhiu bit l lng nhau

X l nhiu bit l song song

Cui chng ny ngi hc s c kin thc xy dng mt chng trnh tng mnh

trong cc tnh hung gy li thng thng u c nm bt gii quyt.

II. Bit l (Exception)

II.1. Chng trnh v li

Chng trnh (theo quan im ca cng ngh thng tin) l mt khi nim dng ch tp

hp cc mnh lnh c trt t m da vo my tnh s thi hnh. Qu trnh con ngi son

tho tp hp cc lnh cho chng trnh c gi l lp trnh. Trong qu trnh lp trnh, c th

v l do ny hoc l do khc m kt qu thu c ca chng trnh khng nh mong mun,

nhng tnh hung khng mong mun nh th gi chung l li (error hoc defect).

Trong lnh vc lp trnh, li thng c chia thnh 2 loi chnh: li tin bin dch (pre-

compiled error) v li khi thc thi (runtimed error).

Li tin bin dch (pre-compiled error) l nhng li xut hin ngay khi xy dng chng

trnh v c trnh bin dch thng bo trong qu trnh bin dch t ngn ng lp trnh sang

ngn ng my hoc ngn ng trung gian. Cc li thuc dng ny thng thng l cc li lin

quan n c php, lin quan n khai bo d liu hoc lin quan cc cu lnh vn c h tr

sn. Cc li tin bin dch thng thng khng nghim trng v thng c pht hin cng

nh chnh sa d dng. Mt s IDE hin ny h tr vic kim tra li t ng ngay trong qu

trnh son tho iu lm cho cc li v cu trc gim i ng k. Cc IDE h tr tnh nng

ny bao gm: Visual Studio (tt c cc phin bn), NetBean, Eclipse, Jbuilder,

Li khi thc thi (runtimed error) l nhng li xy ra khi chy chng trnh. y l mt

dng li tim n v khi chng trnh chy n mt trng thi nht nh mi sinh ra li. Cc li

thuc dng ny rt nghim trng v rt kh khc phc v lc , chng trnh c bin

dch sang m my hoc m trung gian. Cc li thuc dng ny thng c rt nhiu nguyn

nhn: c th do thut ton, c th s khng tng thch ca h thng khi d liu gin n, hoc

cng c th do chnh ngi lp trnh khng lng ht c tt c cc trng thi c th xy ra

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35

i vi chng trnh. C mt vi v d c th cho cc li dng ny m ngi lp trnh thng

gp phi nh: li khi chuyn kiu t kiu chui k t sang kiu s nguyn, li khi truy xut

n phn t nm ngoi mng, li khi kt ni c s d liu,

II.2. Khi nim bit l

Bit l (Exception) l khi nim c s dng trong cc ngn ng lp trnh bc cao dng

ch nhng bin c khng mong i khi chy chng trnh. Bn cht bit l l nhng li

xy ra trong qu trnh thc thi (runtimed error).

Cc ngn ng lp trnh bc cao nh Java v .Net u cung cp mt c ch x l bit l

(gi l c ch try/catch) v c t cc lp c trng cho tng dng bit l m mt chng

trnh thng gp.

III. X l bit l (Exception Handler)

III.1. C ch try/catch

C ch try/catch l c ch c Visual Studio a ra x l cc bit l. C ch ny c

lp trnh theo c php sau:

try

{

harmful-statement(s);

}

catch (Exception-type identifier)

{

behavior-statement(s);

}

[finally

{

final-statement(s);

}]

Cc lnh c nguy c gy li (harmful-statement(s);) c t trong khi try. Cc lnh ny

c th bao gm cc lnh chuyn i kiu d liu (t kiu chui sang kiu s), lnh lin quan

n nhp xut v thm ch c ton t chia Khi gp mt lnh gy ra li trong khi try,

chng trnh thc thi s lp tc triu gi cc lnh trong khi catch tng ng thc thi.

Khi catch l khi lnh thc hin cc ng x khi c li, trong khi ny, thng thng

ngi lp trnh thc hin vic hin th li. Khi xy dng khi catch, u tin phi khai bo

loi bit l (Exception-type). Tt c Exception-type l nhng lp k tha t lp Exception.

Trong mi lp u c phng thc ToString(), phng thc ny c dng hin th thng

tin li cho ngi s dng. Vi mi dng cu lnh s c mt Exception-type tng ng, ngi

lp trnh xem hng dn chi tit ca cc phng thc trong b hng dn MSDN chn

Exception-type tng ng. Trong trng hp ngi lp trnh khng quan tm n cc loi

bit l, ngi lp trnh c th s dng dng c bn l Exception cho tt c cc bit l.

Phng thc ToString() thch hp s t ng triu gi da theo tnh a hnh ca hng i

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36

tng (Polymorphism) v chng trnh lun hin th chnh ni dung li cho d tt c cc dng

bit l u khai bo chung l Exception.

Khi lnh finally c dng cha cc lnh x l cui cng (final-statement(s)). Cc

lnh trong khi lnh ny c t ng triu gi cho d cc lnh trong khi try c sinh ra li

hay khng. Ngi lp trnh khng nht thit phi khai bo khi lnh finally, tuy vy, khi

lnh ny rt hu ch trong vic thu dn rc hoc gii phng vng nh.

V d sau trnh by vic tnh bnh phng ca mt s nguyn c nhp t bn phm. Nu

d liu nhp vo khng phi s nguyn th chng trnh s bo li.

Hnh 40 V d v x l bit l

Trong v d trn, lnh Convert.ToInt32() thc hin vic chuyn t kiu chui k t sang

kiu s nguyn v lnh ny c kh nng sinh ra li khi chui k t nhp vo khng ng nh

dng s nguyn. Khi xy ra li th chng trnh s khng chy nhng dng tio theo trong

khi try m chuyn sang khi catch. Trong khi catch, cc lnh hin th li c thc hin.

Trong trng hp d liu c nhp vo ng nh dng ca kiu s nguyn, chng trnh

s chy ng kt qu nh sau.

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Hnh 41 Kt qu chy chng trnh vi gi tr u vo hp l

Trong trng hp d liu nhp vo khng ng vi nh dng s nguyn, chng trnh s

bo li v hin th c th li ra mn hnh.

Hnh 42 Kt qu chy chng trnh khi xy ra bit l

Trong khi catch, lnh e.ToString() thng c gi hin th li, li ny c hin th

chnh xc vi ni dung li v dng m sinh ra li. Vi c ch x l li ny, ngi lp trnh d

dng tm ra li v chnh sa ph hp.

III.2. X l bit l lng nhau

Trong qu trnh lp trnh, c mt s tnh hung m chng trnh phi thc hin nhiu lnh

c kh nng gy li lin tip. nm bt li mt cch chnh xc, lp trnh vin thng thc

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38

hin vic bt li theo tng bc, ngha l x l bit l ca lnh ny xong th s x l bit l

lnh tip theo.

V d sau y trnh by vic lp trnh tnh s d khi chia s nguyn x cho s nguyn y,

hai s nguyn ny c nhp t bn phm. Trong v d ny, chng trnh c hai lnh c kh

nng sinh li. Lnh th nht l lnh chuyn kiu khi thc hin vic chuyn t kiu chui k t

sang kiu s thc, lnh ny gy ra bit l khi chui k t c nhp vo khng ng nh

dng s thc. Lnh th hai l lnh thc hin php chia ly s d (%), lnh ny gy ra bit l

khi s chia bng 0.

Hnh 43 Minh ha vic s l cc bit l lng nhau

Trong v d trn, khi lnh try/catch bn trong thc hin vic x l bit l khi chia s x

cho s y ly s d. Nu y = 0 th bit l c to ra, bit l ny thuc lp

DivideByZeroException. Khi lnh try/catch bn ngoi thc hin vic x l bit l khi chuyn

kiu t kiu s chui k t sang kiu s nguyn (Xem chi tit phn III.1 trc ).

Trong trng hp c hai s nhp vo x, y u c nh dng ph hp v y khc 0 th

chng trnh chy v cho ra kt qu ng (Nh hnh).

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Hnh 44 Kt qu chy chng trnh vi gi tr u vo hp l

Trong trng hp mt trong hai s nhp vo c nh dng khng phi l s nguyn th bit

l u tin c x l. Khi chng trnh s thng bo li v chng trnh khng tip tc

chy thc hin php ton chia (Nh hnh).

Hnh 45 Bit l xy ra khi gi tr nhp vo khng ng nh dng s nguyn

Trong trng hp c hai s nhp vo ng nh dng s nguyn nhng y c gi tr 0 th

bit l tip theo c x l. Trong trng hp ny php chia ly s d s khng thc hin

c v chng trnh s thng bo li (Nh hnh).

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Hnh 46 Bit l xy ra khi s chia bng 0

Vi v d trn, ta c th d dng nhn thy vic x l bit l lng nhau mt cch phn cp

s lm cho chng trnh cht ch v li c nm bt d dng. Vi mi bit l c thng

bo ra mn hnh, ngi lp trnh s d dng nhn thy v chnh sa on m ph hp. Tuy

nhin, vic x l nhiu bit l lng nhau mt cch phn cp lm cho m ngun tr ca

chng trnh thm nng n, cc khi try/catch xut hin nhiu ln v lng nhau lm cho cu

trc ca chng trnh tr nn phc tp.

III.3. X l bit l song song

Nh trnh by phn III.2, khi c nhiu lnh c kh nng gy ra bit l th ta cn phi

thc hin x l tt c cc bit l. x l cc bit l, ta thc hin vic s dng cu trc

try/catch mt cch tun t: lnh no thc hin trc th x l trc, sau , ngay bn trong

khi try, ngi lp trnh s dng mt cu trc try/catch khc x l bit l cho lnh tip

theo. Cch lm ny tuy x l tt c cc bit l nhng cng lm cho chng trnh tr nn phc

tp v phi s dng nhiu cu trc try/catch lng nhau. ti u ha m lnh v lm cho

chng trnh thm tng minh, thng thng ngi lp trnh thc hin vic x l bit l song

song.

X l bit l song song l qu trnh x l bit l trong ch c mt khi try nhng li c

nhiu khi catch. Tt c cc lnh cn thit u t trong khi try v mi khi catch s thc

hin vic bt mt bit l tng ng. Khi chy chng trnh, ng vi mt bit l c to ra,

chng trnh thc thi ca .Net Framework s t ng tham chiu n khi catch c bit l

tng ng gi lnh x l.

V d sau trnh by vic ci tin v d mc III.2, trong v d ny, bit l c x l bng

cch s dng hai khi catch khc nhau bt ly 2 bit l khc nhau. Kt qu chy chng

trnh ci tin ny hon ton ging vi kt qu khi chy v d trong mc III.2

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Hnh 47 X l nhiu bit l song song

L Vn Minh Trng Cao ng Cng ngh Thng tin, i hc Nng 42

Chng 5

TH VIN LIN KT NG

I. Mc tiu

Sau khi hiu c nguyn l Lp trnh hng i tng vi C#, ngi lp trnh c th t

xy dng c cc lp theo s c t ca bi ton thc t. Tuy nhin, ng dng tr nn

trong sng v khoa hc, cc lp cn c phn loi v tp hp thnh cc th vin. Cc th

vin ny khng nhng gip cho ngi lp trnh d dng tm kim, cp nht, nng cp chnh

m ngun ca mnh m cn gip cho vic pht trin cc ng dng sau ny mt cch d dng

bng cch s dng li cc th vin c. Trong chng ny gio trnh s trnh by mt s

khi nim lin quan n vic xy dng th vin trong cc ngn ng thuc h .Net m tiu

biu l ngn ng lp trnh C#.. Nhng ch chnh c trnh by trong chng ny bao

gm:

Namespace

Th vin lin kt ng

Cch xy dng mt th vin

Cch s dng mt th vin

Mt s th vin v namespace c sn

Cui chng ny ngi hc s c kin thc c th phn chia ng dng ca mnh

thnh nhng phn ring bit mt cch khoa hc tin cho vic pht trin sau ny.

II. Th vin trong lp trnh

II.1. Khi nim

Khi lp trnh, ngi lp trnh khng nht thit phi nh ngha mi th m c th s dng

nhng on chng trnh t nhng ngi khc hoc nhng on chng trnh t mt ng

dng trc ca chnh mnh. Do , khi lp trnh, ngi lp trnh cn phi nhng vo

chng trnh ca mnh mt hoc nhiu on m ca chng trnh khc.

Trong lp trnh, th vin l mt khi nim dng ch tp hp cc on m hoc on

chng trnh m cc on m ny c nhng vo mt chng trnh khc nhm phc v mt

s chc nng xc nh. V d cc th vin phc v lp trnh ha, cc th vin iu khin

phn cng (cn c bit n vi thut ng driver),

Vic s dng th vin c mt ngha v cng thit thc khi ngi lp trnh cn phi thc

hin vic iu khin mt s thit b c th hoc lp trnh giao din hoc kt ni vi h thng

phn cng, v ngi lp trnh khng th hiu ht ton b thng tin v cc thit b cng nh h

thng ha v phn cng do cc thng tin ny c nh sn xut cung cp. Thng

thng, cc thng tin v phn cng v thit b c nh sn xut cung cp cho ngi lp trnh

di dng th vin.

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II.2. Phn loi th vin

i vi vic lp trnh ng dng, th vin thng c phn loi da vo vic nhng th

vin vo chng trnh. Vi tiu ch ny, th vin c phn thnh hai loi: th vin tnh

v th vin lin kt ng

II.2.1. Th vin tnh

Th vin tnh l khi nim ch on m hoc on chng trnh c nhng trc tip vo

mt chng trnh khc. Nhng on m ca th vin tnh c th l m chng trnh hoc m

tin bin dch (pre-compiler code mt dng m rt gn c hiu bi mt ngn ng lp

trnh c th). Khi bin dch, c m ngun ca chng trnh ln m ca th vin tnh c

bin dch cng mt lc thnh m thc thi hoc nh phn (m my) v cha trong mt file ca

chng trnh.

i vi ngn ng C th vic s dng th vin tnh c thc hin thng qua lnh #include,

lnh ny thc hin vic nhng ton b on m ca th vin c gi vo chng trnh m

ngi lp trnh ang s dng.

Vic s dng th vin tnh tuy gip cho ngi lp trnh s dng li nhng on m xy

dng nhng cch lm ny vn c hai nhc im c bn:

Lm tng ln ca chng trnh: Khi nhng nhiu nhiu th vin vo mt chng

trnh th dung lng ca chng trnh s phi tng thm v cha thm m ngun ca

cc th vin cho d ngi lp trnh ch s dng mt t chc nng ca th vin .

Ngoi ra, khi mt th vin tnh c nhng vo nhiu chng trnh th tt c cc

chng trnh u tng dung lng.

To ra s khng ng b khi cp nht: Khi ngi lp trnh chnh sa th vin th kt

qu vn khng c cp nht vo cc chng trnh vn nhng th vin .

chng trnh c s cp nht ng b, ngi lp trnh bt buc phi bin dch li

chng trnh ton b m ngun ca chng trnh c bin dch li vi phin bn

mi nht ca th vin.

gii quyt hai nhc im trn, Microsoft ra gii php Th vin lin kt ng

Dymamic Linked Library gi tc l dll.

II.2.2. Th vin lin kt ng

Th vin lin kt ng (Dynamic Linked Library) l khi nim c Microsoft a ra khi

xy dng h iu hnh Windows. Th vin lin kt ng c dng ch nhng on

chng trnh hoc nhng on m nh phn nm trong mt file (thng thng c phn m

rng l .dll) m nhng on m ny c th c cc chng trnh khc gi bng cc tham

chiu thay v phi nhng ton b on m vo chng trnh.

Vi th vin lin kt ng, cc chng trnh s gim bt dung lng v rt nhiu chng

trnh c th s dng chung mt th vin, c bit l cc th vin ca h thng nh th vin

ha, cc driver iu khin thit b. Vic s dng th vin lin kt ng s to ra s ng b

khi lp trnh v chnh sa v ch cn chnh sa ngay ti th vin, tt c cc chng trnh c s

dng th vin s t ng thay i m khng cn phi bin dch li.

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Khc vi th vin tnh, cc on m cha trong th vin lin kt ng l nhng on m

thc thi c (executable code). Cc on m ny nu c gi ng cch th vn c th th

thi c. iu ny cng ny sinh nhc im l cc th vin lin kt ng vn c th b

nhim virus. Nhng virus ny tuy khng lm gin on chng trnh nhng c th lm cho

chng trnh b li hoc chy sai kt qu. Cc li ny s lm cho ngi lp trnh kh c th

chnh sa ng n v ngi lp trnh khng c kh nng can thip vo cc th vin ca cc

nh cung cp.

Trong cc ngn ng thuc h .Net, cc lp trong cc th vin c phn nhm. Nhng

nhm ny c gi l namespace.

III. Namespace

Namespace cn c bit di mt thut ng khc l khng gian tn. Namespace l mt

khi nim c a vo h ngn ng .Net t phin bn Visual Studio 2003. Namespace c

dng ch mt nhm cc lp trong mt th vin.

Khi nim namespace gip cho vic t chc cc th vin c trong sng, d dng. Ngoi

ra, namespace cn gip ngi lp trnh trnh n s xung t v tn lp, tn hm, tn cc kiu

d liu khi cc tn ny b trng.

Nhiu namespace c th c t lng nhau v ngi lp trnh c ty t tn cc

namespace nh cch t tn bin. Tuy nhin, thng thng namespace c t tn theo mt

quy c chung ca mt chun phn mm. Quy c v vic t tn namespace thng thng

bao gm tn doanh nghip, tn d n, tn module v c phn cch vi nhau bi du chm

(dot) nh: ..

V d: namespace Wrox.ProCSharp.Basics;

IV. Th vin lin kt ng

IV.1. Cch xy dng th vin vi Visual Studio 2005

Trong phn ny, gio trnh s hng dn xy dng mt th vin c tn l MyLibrary. Th

vin ny cha namespace m namespace ny tp hp cc lp c cc hm hin quan n cc

cng thc ton hc. xy dng th vin ny, ngi lp trnh c th thc hin theo cc bc

sau.

IV.1.1. To mt project cho th vin

Khi to project cho th vin, project ny c template l Class Library. Vic khai bo tn

v th mc c th hin tng t nh vic to Console Application project trnh by

phn trn. V d sau minh ha vic to mt th vin c tn l MyLibrary.

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Hnh 48 To mi mt project Library

IV.1.2. Cu hnh cho project

Trong bc ny chng ta s thit lp namespace mc nh cho th vin v thit lp ng

dn cho th vin. Khi to cc lp cho th vin th cc namespace mc nh ny s t ng

c gn cho cc lp. ng dn ca th vin chnh l v tr ca file .dll sau khi Visual

Studio bin dch thnh cng.

Hnh 49 Minh ha vic cu hnh namespace mc nh

Vi minh ha hnh trn, namespace mc nh c t tn theo chun gm tn doanh

nghip, tn d n, tn module l MyCompany.CSharp.MathLibrary. Namespace ny c

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dng ch tp hp cc lp c cc hm lin quan n cc cng thc ton hc. Sau khi thit

lp namespace mc nh, ngi lp trnh s thit lp thm ng dn ca th vin.

Hnh 50 Minh ha vic thit lp ng dn cho th vin

Vi minh ha hnh trn th ng dn ca th vin l th mc bin, th mc ny nm

ngay trong th mc cha project. Sau khi bin dch thnh cng, file MyLibrary.dll s c

to ra ngay trong th mc bin ny.

Trong phn cu hnh cho project cn c nhiu tham s khc. Ty vo yu cu c th,

ngi lp trnh c th cu hnh theo ca chnh mnh. Cc tham s khc v cu hnh, ngi

hc t nghin cu v tm hiu thm.

IV.1.3. Xy dng lp v phng thc cn thit

Trong bc ny, ngi lp trnh c th xy dng cc lp. Trong cc lp, cc thuc tnh v

phng thc c xy dng theo nguyn l lp trnh hng i tng. Khi xy dng cc lp

trong th vin, v cc lp ny cn c truy xut t mt ng dng khc (truy xut t bn

ngoi), do ch dn truy cp ca cc lp thng thng l public. V d sau trnh by vic

xy dng mt lp trong th vin, lp ny c tn l MyMath. Trong lp MyMath, v d trnh

by vic xy dng mt phng thc IsPrime(int x), phng thc ny l mt hm thc hin

vic kim tra mt s c phi l s nguyn t hay khng. Phng thc IsPrime tr v true nu

gi tr u vo l s nguyn t v tr v false nu ngc li.

Visual Studio t phin bn 2003 tr i cung cp mt gii php vit ch thch (write

commnent) cho c mt phng thc. Vi gii php ny cc ghi ch ca mt phng thc

c ghi thnh tng dng v bt u bng ba du chia (triple slashes). Ngi lp trnh s vit

ghi ch v ghi ch ny c s dng nh mt hng dn cho nhng ngi lp trnh sau ny

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khi s dng. Ch , ngi lp trnh c th son tho ghi ch bng Ting Vit c du theo

chun Unicode.

Hnh 51 Minh ha vic xy dng lp trong th vin

IV.2. Cch s dng th vin

Lp trnh vin Visual Studio .Net c th s dng mt s th vin c sn dng file .dll m

file ny cng c xy dng bng Visual Studio .Net. i vi Visual Studio .Net, cc th

vin bng nhng ngn ng khc nhau (trong h .Net) c th tham chiu ln nhau v cng c

th c s dng bi nhng chng trnh khc trong h .Net. Trong phn ny gio trnh s

trnh by mt v d thc hin vic s dng phng thc IsPrime(x) ca th vin trn. V d

ny thc hin vic hin th tt c cc s nguyn t nh hn 100. s dng th vin va

c xy dng, ta thc hin cc bc sau.

IV.2.1. To thm tham chiu (add reference).

to tham chiu n th vin, ta thc hin vic kch chut phi (right click) vo mc

References trong ca s Solution Explorer ri chn Add Reference. Vic to thm tham chiu

bn cht l s khai bo ng dn n th vin cn tham chiu.Vi khai bo ny, trnh bin

dch s thc hin vic truy xut n cc file .dll v s dng cc lp, phng thc trong cc

file .

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Hnh 52 To thm tham chiu cho ng dng

IV.2.2. Khai bo tham chiu

Trong phn ny, Visual Studio s cung cp cho ngi lp trnh mt giao din ty chn

ngi lp trnh la chn mt th vin tng ng. Trong giao din ny c cc th (tab) tng

ng vi tng loi th vin bao gm: th .NET cha cc th vin c sn ca .NET Framework,

th COM cha cc th vin ca ng dng COM, th Project cha cc Project c dng th

vin trong cng Solution, th Browse cha ty chn n file .dll c lp.

Hnh 53 Khai bo tham chiu

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Trong phn ny, gio trnh trnh by vic tham chiu n mt th vin c lp bng cch

la chn n file .dll trong th Browse. C th trong v d hnh trn l file MyLibrary.dll

trong th mc bin ca project MyLibrary vn c trnh by phn trc.

IV.2.3. S dng th vin

Sau khi khai bo tham chiu, ngi lp trnh s phi khai bo vic s dng namespace

trong th vin. Namespace ny c khai bo bng lnh using. Lnh ny c c php v chc

nng tng t vi lnh import ca ngn ng Java (ca hc phn lp trnh Java trc ).

Khi s dng, ngi lp trnh thc hin vic khai bo i tng hoc vic triu gi phng

thc ging nh vic s dng cc lp c sn. Nu trong qu trnh xy dng th vin, ngi lp

trnh c thc hin vic vit ch thch cho cc phng thc th khi triu gi, cc ghi ch ny s

c hin th nh cc hng dn ca cc phng thc c sn ca .Net Framework.

Hnh 54 Minh ha vic s dng th vin

Hnh trn trnh by vic s dng hm IsPrime(x) ca th vin MyLibrary. Hm ny thuc

lp MyMath v c nhm vo namespace MyCompany.Csharp.MathLibrary.

V. Cc namespace c sn ca .Net Framework 2.0

V.1. Namespace System.Windows.Forms

Namespace System.Windows.Forms cha cc lp dng to ng dng Windows vi giao

din ngi s dng mang cc c im u vit ca h iu hnh Windows.

y l namespace chnh cung cp cc lp dng xy dng ng dng Windows c

trnh by trong chng tip theo. Cc lp trong namespace ny c chia thnh cc nhm

sau:

Control, UserControl v Form: Hu ht cc lp trong namespace

System.Windows.Forms k th