indrumator ii

7/25/2019 Indrumator II

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Technical University of Cluj-Napoca

Faculty of Automation and Computer Science

Industrial Informatics

Author:

Asist.dr.eng. Emilia-Daniela

Bordencea

Author:

Prof.dr.eng. Honoriu

Valean

2012


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Contents

Contents iii

List of Figures vii

1 Console Applications 1

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 C#syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.1 Identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.3 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.4 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2.5 Data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.6 Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.2.7 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.2.8 Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.3 My first C#application . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.4 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2 Windows Form Applications 17

2.1 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.1.1 Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.2 Multiple forms applications . . . . . . . . . . . . . . . . . . . . . . . . 26

2.3 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

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3 Threads 29

3.1 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.1.1 Creating threads . . . . . . . . . . . . . . . . . . . . . . . . . . 303.1.2 Naming Threads . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.3 Join and Sleep methods . . . . . . . . . . . . . . . . . . . . . . 31

3.2 Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.2.1 Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.2.2 Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.2.3 Mutex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.2.4 Semaphore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4 Database 39

4.1 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.1.1 Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.1.2 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4.1.3 DataReader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

4.1.4 DataSet and DataAdapter . . . . . . . . . . . . . . . . . . . . . 42

4.1.5 DataTable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

4.1.6 DataRelation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424.2 My first database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.2.1 Connect to the MS SQL Server Express Database . . . . . . . 45

4.3 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5 Web Services 49

5.1 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

5.2 Create a Web Service client . . . . . . . . . . . . . . . . . . . . . . . . 53

5.3 Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

6 Windows Presentation Foundation 57

6.1 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

6.1.1 Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

6.1.2 Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

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6.2 Styling and Data Binding . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.2.1 WPF vs Windows Forms . . . . . . . . . . . . . . . . . . . . . 62

6.2.2 Styles in WPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 636.2.3 Data Binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

6.3 Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

6.4 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Bibliography 69

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List of Figures

1.1 Creating a Console Application . . . . . . . . . . . . . . . . . . . . . . 10

1.2 Solution Explorer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.3 IntelliSense feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.4 Hello C#Application . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.5 How to run an application in command line . . . . . . . . . . . . . . . 13

2.1 Creating a Form Application . . . . . . . . . . . . . . . . . . . . . . . 17

2.2 Form Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.3 My First Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.4 Get text from a TextBox (1) . . . . . . . . . . . . . . . . . . . . . . . 23

2.5 Get Text from a TextBox (2) . . . . . . . . . . . . . . . . . . . . . . . 24

2.6 String concatenation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.1 Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.2 Join method output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.1 ADO architecture. Source: [1]. . . . . . . . . . . . . . . . . . . . . . . 39

4.2 Creating a database in C# . . . . . . . . . . . . . . . . . . . . . . . . 40

4.3 Creating a database in c# . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.4 Choose your Data Connection . . . . . . . . . . . . . . . . . . . . . . . 46

5.1 Web Services Triangle Architecture. Source: [2] . . . . . . . . . . . . . 49

5.2 Creating a Web Service . . . . . . . . . . . . . . . . . . . . . . . . . . 50

5.3 Solution Explorer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

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LIST OF FIGURES

5.4 Web Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.5 Add service reference (1) . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5.6 Add service reference (2) . . . . . . . . . . . . . . . . . . . . . . . . . . 535.7 Add service reference (3) . . . . . . . . . . . . . . . . . . . . . . . . . . 54

6.1 Creating a WPF Application . . . . . . . . . . . . . . . . . . . . . . . 58

6.2 WPF button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

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Chapter 1

Console Applications

This chapter presents the basic programming concepts in C# by introducing some

console applications.

1.1 Introduction

C# was developed by a small team of engineers at Microsoft. Anders Hejlsberg (the

Turbo Pascal language author and member of the team which designed the Borland

Delphi) is one of the creators. C# is an object-oriented imperative programming

language. It is very similar to Java and C++, and this is why the learning curve runs

very smoothly.

C# uses Microsoft .NET Framework, a collection of classes which can be down-

loaded through the Internet and which is constantly maintained and improved by

Microsoft.

The .NET applications are run in a program compilation called CLR (Common

Language Runtime). The initial compilation of the program generates a code written

in an intermediate language (CIL - Common Intermediate Language). In this form,

the code is then sent to the virtual processor (CLR) that performs the translation to

machine code and that runs the application.

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1. Console Applications

1.2 C# syntax

This language inherits the C++ syntax and programming principles. Furthermore,

some new data types and methods were added, modified or dumped.

1.2.1 Identifiers

The identifiers are used to indicate variables, data types, symbolic constants or meth-

ods. The first character of an identifier must be a letter or underline, and its maximum

length cannot exceed 31 characters.

1.2.2 Keywords

The keywords are predefined identifiers with special meaning for the compiler. The

C#keywords are presented below:

abstract as base bool break

byte case catch char checked

class const continue decimal default

delegate do double else enum

event explicit extern false finally

fixed float for foreach goto

if implicit in int interface

internal is lock long namespace

new null object operator out

override params private protected public

readonly ref return sbyte sealed

short sizeof stackalloc static string

struct switch this throw true

try typeof uint ulong unchecked

unsafe ushort using virtual void

volatile while

Generally, the keywords cannot have a different meaning in our programs. However,

in order for them to have another meaning, they must contain the symbol @ as a prefix.

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C# syntax

1.2.3 Variables

A variable can contain either a value of an elementary type or a reference to an

object. In C#, a variable is declared by writing its type and name. They are optionally

initialized through the assignment of a value.

1 / / D e c l a r e2 i n t a ;3 // I n i t i a l i z e4 a =1 ;5 // D ec la re and i n i t i a l i z e6 i n t c =1 ;7 // M u l ti p le v a r i ab l e can be d e cl a r ed in o ne s ta te me nt i f

t h ey h av e t h e same t y pe8 i n t first, second;9 // D ec la re and i n i t i a l i z e

10 i n t bfirst =1 , bsecond =2 ;

Note: C# is "case sensitive", it distinguishes between uppercase and lowercase

letters.

1.2.4 Constants

The constants are values which cannot change. They can be declared by using the

const or the readonlymodifier.When local variables or fields are declared using the

constmodifier, they must be initialized. The constants are implicitly static.

1 co ns t i n t ct = 3 ;

On the other hand, the readonlyfields can be initialized within a constructor.

1 // I n i t i a l i z e a r e ad on ly f i e l d

2 p u bl i c r ea do nl y i n t ct = 3 ;

3 p u bl i c r ea do nl y i n t cn t;

4

5 p u b l i c my C ( )

6 {

7 // I n i t i a l i z e a r ea do nl y i n s ta nc e f i e l d

8 cn t = 4 ;

9 }

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1.2.5 Data types

Two categories of data types exist in C#:

value types;

reference types.

Value types

Examples:

byte, short, int, float, double, long, char, bool, DateTime;

primitive data types except string, object;

struct;

enum.

Date time:

1 D a te T i m e c u r r e n t t im e = DateTime.N ow ; / / i t d i s p l a ys t he c u rr e nt d at etime

2 i n t days = DateTime. DaysInMonth ( 2 0 1 1 , 7 ) ; / / i t d i s p l a y s " 3 1"

Reference types

Examples: class, interface, delegate, string, object and array.

Note: You might observe that C# contains two types of strings,stringand String,

and you also might wonder what is the difference. Technically, excepting a few small

differences, there are the same (string is an alias for System.String). Then, maybe you

are wondering when it is recommended to use one or the other. Generally, you can

use string when you refer to an object (string mystr="hi";) and you can use String

when you refer to the class (string reply = String.Format("0", mystr);). Among the

differences, we have:

String is a class name while string is a restricted keyword,

String belongs to the .NET platform (is accessible in all languages), while string

is language specific (C#).

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C# syntax

The arrays are zero indexed in C# and they work almost the same as in other

languages.

The declaration is:

1 i n t[ ] array; // n ot i n t a r ra y [ ] ;

Note: It is not legal to place the brackets after the identifier in C#.

C#supports:

single-dimensional arrays,

multidimensional arrays (rectangular arrays),

array-of-arrays (jagged arrays).

1. single-dimensional arrays

The declaration is:

1 i n t [ ] myArray;

The array is declared but not created. For creating the arrays, it must be

instantiated.

1 i n t [ ] myArray = new i n t [ 1 0 ] ;

2. multidimensional arrays (rectangular arrays)

1 s t r i n g[ , ] myArray;2 myArray = new s t r i n g [ 7 , 6 ] ;

3. array-of-arrays (jagged arrays)

1 b y te[ ] [ ] scores;2 scores = new b y te[ 5 ] [ ] ;3 f o r (i n t x = 0 ; x < scores. Length; x++)4 {5 scores[ x ] = new b y te[ 4 ] ;6 }

You can have three-dimensional rectangular arrays or mix rectangular and jaggedarrays.

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1 i n t[ , , ] buttons = new i n t [ 4 , 5 , 3 ] ; / / t h r e ed i m en s io n a l r e c t a n g u l a ra r r a y

2 i n t[ ] [ , , ] [ , ] numbers; / / s i n g l e d i m en s i on a l a r ra y o f t h re ed i m en s i on a l a r r a y s o f twod i me ns i on a l a r ra y s o f t yp e i n t

1.2.6 Operators

The operators are used for specifying which operations should be performed in an

expression.

Assignment and Equality Operators

= Assigns a value

== Tests for equality

Increment and Decrement operators

v++ Increment variable v by 1

v += n Increment variable v by nv=v+n;

v *= n Multiply variable v by n

v -= n Subtract n from variable v

Example of pre and post-increment operators:Example:

1 x = n++; // s e t s x=n , a nd t h e n s e t n=n+12 x = ++n ; / / s e t s n=n +1 , a nd t he n s e t x = th e n ew v a lu e o f n

Mathematical and Logical Operators

+ Addition

- Subtraction

* Multiplication

/ Division

% Modulus

& Logical AND

Logical XOR

| Logical OR

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C# syntax

The arithmetic expression evaluation is performed from the left side to the right

side, taking into account the order of regular assessment.

Logical Condition Operators

&& Conditional AND

|| Conditional OR

! Conditional NOT

The && operator has higher priority than the || operator and smaller priority than

the comparison operators. In && and || operations, the terms used represent bool

values.

Note: The rule from C, in which a numerical value different than 0 is true and a

value equal to 0 is false, is not valid in C#.

Relational operators

== Checks for equality

!= Checks for inequality

> Greater than

< Less than

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In order to convert strings to some other types, .Parse can be used. There are, for

example, strings which contain digits. In order to use the numerical value, the string

should be converted to an integer.

1 s t r i n g myText = " 2 0 ";2 i n t myNum = i n t. Parse (my Te xt ) ; // I t c on ve rt s s t r i n g t o

i n t e g e r .

Another C# method for parsing integers is int.TryParse. The difference between

int.TryParse and int.Parse is represented by the fact that, the first one can be used

when the data is corrupt. For example, when the data does contain non-numeric or

invalid characters, int.TryParse should be used. If the data is valid and consists only

of numbers, int.Parse is a good solution.

1.2.7 Comments

In the case of all the programming languages, for explaining the meaning of different

methods or variables, the programs can contain text under the form of comments. The

following types of comments [3]can be used in C#:

Single line comments //one line comment;

Multiple line comments, used especially for debugging / multi line comments/;

XML tag comments /// XML tag comments.

Single line comments are used in the majority of cases.

Shortcuts: Ctrl+K and then Ctrl+C to comment selected lines of text and

Ctrl+K and then Ctrl+U to uncomment.

1.2.8 Files

In order to work with files in C#, System.IO directive is used.

Writing in a file is done by using StreamWriter:

1 S t re a m W r i t e r s w = new StreamWriter (" myFile . txt ", t r u e) ;

2 sw. WriteLine (" I am a f i l e ! ") ;

3 sw. Close( ) ;

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C# syntax

Reading from a file:

1 S tr e a m R e a d e r s r = new StreamReader (" myFile . txt ") ;

2 s t r i n g line = sr .ReadLine( ) ;

3 sr. Close( ) ;

Split the line into words:

1 c h a r[ ] separator = { } ;

2 s t r i n g[ ] words = line. Split ( separator, S t r i n g S p l i t O p t i o n s.

R e m o v e E m p t y E n t r i e s) ;

Note: When you want to clear the buffer and leave the stream open, you can use

StreamWriter.Flush(). This method writes the current contents of the buffer to the

file. In order to close the stream, you can use StreamWriter.Close(). This method

internally calls flush() method and before closing the stream it flushes the Steeam for

the last time. Invoking the flush method makes sure that the memory contents are

persisted to disk; thus, the buffer data is not lost in case the process or machine fails.

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1.3 My first C# application

The way to create a console application is fairly simple: select File New Project

Visual C# Console Application (Figure1.1). The project can be renamed and

the location of the project can be changed.

Figure 1.1: Creating a Console Application

When a console application is created, a .cs file is generated. The .csextension

comes from C Sharp.

All the project files can be found in Solution Explorer(Figure1.2). If the Solution

Explorer cannot be seen, it can be made visible from the View menu or by using the

shortcut Ctrl+W, S.

Figure 1.2: Solution Explorer

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My first C# application

In Listing1.1,the structure of a C#program is presented.

Listing 1.1: The structure of a C#program1 u s i n g System;2 u s i n g System. Collections. Generic;3 u s i n g System. Linq;4 u s i n g System. Text;56 namespace myFirstApp7 {8 c l a s s Program9 {

10 s t a t i c v oi d Main (s t r i n g[ ] args )11 {12

13 }14 }15 }

This is the code that is executed when the application is running. The first line

(using System) is a directive which specifies that some of the Systemnamespace classes

will be used. MyFirstAppis the applications name. There also exists a classProgram

which contains the Mainmethod.

Therefore, a C# application consists of one or more classes, grouped in namespaces.

Lets take a look at the code. Only one of the classes must contain an entry point (the

Main method).

Convention: The following writing convention is also adopted in C#: if names

consisting of several words are used, each word is capitalized: HelloWorld, WriteLine.

The convention is called the Pascal Convention. The Camel Case Convention is similar,

except that the first character of the first word is lowercase.

Lets make a simple console application. Write a simple program as in Figure1.4.

You can observe that you are assisted by the IntelliSense (Figure 1.3), the feature

which helps you to automatically generate the code in the Code Editor.

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Figure 1.3: IntelliSense feature

To compile the program, select Build Build Solution from the main menu or

press F6. If errors exist, they will be displayed in the Error List window.

There are many ways to run the program:

Start Without Debugging (shortcut Ctrl+F5)

Start Debugging (shortcut F5)

Step Into (F11) and Step Over (F10) (running step by step)

Toggle Breakpoint (F9) and then Start Debugging (runs fast until the breakpoint

line marked).

Stop Debugging (Shift+F5) exits from the debugging mode and returns to the

normal one. All these options are available in the Debug menu of the programming

environment.

The application code and its result are shown in Figure 1.4.

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My first C# application

Figure 1.4: Hello C#Application

As it can be seen, the last line of the code contains Console.ReadKey(). This line

is used for keeping the console open until a key is pressed. If this line is not present,

the program will be executed and then the console will close.

You can also run the program only using the .exe file from /bin/debug. The result

can be seen in Figure1.5.

Figure 1.5: How to run an application in command line

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Exercises

1.4 Exercises

1. Determine the first n terms of the Fibonacci sequence.

2. Read two real numbers from the keyboard and then, by using the binary opera-

tors +, -, *, /, make some computations.

3. Compute the ideal weight (kg) according to the height (cm), age (years) and

sex. The parameters are read from the keyboard.

Man_idWeight = [height (cm) -100 - ( (-150 ) /4 )] + ( (age-20) /4)

Woman_idWeight = [height (cm) -100 - ( (height-150 ) /2,5)] + ( (age-20) /6)

4. Create a stack. Add to the classStack the public method ElementsNr() whichreturns the elements number inserted in the stack. Do the same thing for a

queue.

5. Create a class named Car with the attributes: name, engine power and price.

Create a static method for comparing two cars. Lets say that power is more

important than the price so, the power will be the first criterion and the price

will be the second one. Create an application which asks for n car models and

sorts them in ascending order.

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Chapter 2

Windows Form Applications

2.1 Getting started

Microsoft Visual C# contains specialized tools, which offer the possibility to create

applications in an interactive, quick and easy way. In order to create Form Applications

click FileNew Project Visual C#and then select Windows Form Application.

Figure 2.1: Creating a Form Application

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2. Windows Form Applications

A window like the one in Figure 2.2 will appear. The windows default name is

Form1. Controls, such as buttons, text boxes, menus, check boxes, radio buttons and

so on can be added to the forms.

Figure 2.2: Form Application

The Windows Form Applications can be formed of at least one Form. The visual

components of the application can be processed in the Designer mode (Shift + F7):

placing new objects, determining their properties and so on. The code "behind" a

visual component is accessible in Code mode (F7).

The code of Form1.cs file can be seen by right clicking and selecting the View Code

option in Solution Explorer. The properties window (Ctrl+W, P) is used for changing

objects properties.

The Toolbox (Ctrl+W,X) contains all the controls and all the components that

can be used. The controls can be dragged-and-dropped and they are clustered in

categories.When a visual application is created, C# generates a namespace which contains

the starting point of the application (the Program class, listing 2.1).

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Getting started

Listing 2.1: TheProgram class

1 u s i n g System;2 u s i n g System. Collections. Generic;

3 u s i n g System. Linq;4 u s i n g System. Windows. Forms;56 namespace MyFirstForm7 {8 s t a t i c c l a s s Program9 {

10 // / 11 / // The main e n tr y po i n t f o r th e a p p l i c a t i o n .12 // / 13 [STAThread]14 s t a t i c v oi d Main( )15 {16 Application. E n a b l e V i s u a lS t y l e s( ) ;

17 Application. S e t C o m p a t i b l e T e x t R en d e r i n g D e f a u l t (f a l s e) ;18 Application. R un ( new Form1() ) ;19 }20 }21 }

The application is executed in the same way as a Console Applications (see chapter

Console Applications).

All the windows contain in the right side a drawing pin, which, if opened, sets

the window upright. Otherwise, the window closes, retreating to the programming

environments right or left side.

2.1.1 Controls

A control is the main unit of a Windows interface. It can be hosted by a container

(for instance, a form or another control).

A control is an instance of a class derived from System.Windows.Forms, being

responsible for drawing a part of a container.

The Table 2.1 contains a list of the most frequently used controls together with

their descriptions.

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Table 2.1: Controls

Control name Description

Button used for executing a sequence of instructions when their are ac-

tivated by the userMonthCalendar displays a calendar of the current monthCheckBox yes/no optionLabel used for printing text labelListBox displays a list of articles from where the user can choosePictureBox used for adding imagesPointer used for selecting, moving or scaling a controlRadioButton gives the possibility of choosing one element from a cluster of

selectionsTextBox displays the text generated by an application or gives the possi-

bility to introduce a text

Buttons

First, lets create a Form Application, as in Figure 2.3,which contains a button.

Figure 2.3: My First Button

For doing this, go to Toolbox and expand Common Controls. Select the Button

element and move the cursor somewhere on the surface of your form.

All the controls have properties. Select the Text property and modify the text that

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Getting started

will appear on your button inMy Button. The form has also a lot of properties. Click

the form and change the text to My First Form. Then change the form size. After

you solve these three requirements, the Form should look like in Figure 2.3.Further, lets add a function to our button. Thus, when the button is clicked, a mes-

sage box should be displayed. How do we do this? First, double-click on the button.

This will automatically generate in the Form code a method called button1_Click.

Button1 is the default button name (because we did not changed the property name

of the button) and _Click is an event. Some other events examples are MouseDown,

LocationChanged, TextChanged, and so on. Object sender, EventArgs eare known as

arguments. One argument is called sender and the other is called e.

As it was said in the beginning, we want to display a message box containing some

text. This is quite simple to be done in C# as it can be seen in the source code,

presented in Listing2.2.

Listing 2.2: Display a MessageBox which contains some text

1 u s i n g System;2 u s i n g System. Collections. Generic;3 u s i n g System. ComponentModel;4 u s i n g System. Data;5 u s i n g System. Drawing;6 u s i n g System. Linq;7 u s i n g System. Text;

8 u s i n g System. Windows. Forms;9

10 namespace MyFirstForm11 {12 p u b l i c partial c l a s s Form1 : Form13 {14 p u b l i c Form1( )15 {16 I n i t i a l i z e C o m p o n e n t( ) ;17 }18 p r i v at e v oi d button1_Click (o b j e c t sender, E v e n t Ar g s e )19 {20 MessageBox. Show ("Me s s a ge ", "My F ir s t Msg ") ; / / d i s p l a ys

a wi ndo w w i t h t h e name " My F i r s t Msg " a nd am es sa ge " M e ss ag e " . I f "My F i r s t Msg " i s o m it t ed ,t h e window w i l l n ot h av e a ny name .

21 }22 }23 }

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Exercise 1: Create an application that contains a button and displays the number

of clicks.

Show() method is used when you want to have access to the main menu form

controls, even if a second menu is active. If you want to have the permission of using

the main menu only when the second menu is closed, you should use ShowDialog()

method. In this case, we can talk about modal forms. DialogResult is a property used

with these methods for identifying which button is clicked by the user.

Exercise 2: Create a form which contains two buttons OK and CANCEL and

displays which button was clicked.

Text boxes

Herein, the text and numerical variables will be introduced. What is a variable? It is

a storage area for things that you will need later on. They can be seen as boxes, which

are empty until something is put inside. They can be labeled for not being confused.

To understand what is going on, a small program will be written. It takes the text

from a text box, retains it in a variable and then displays it through a message.

Thus, create a new Windows Form Application project and rename it as you wish.

Add a button having the following properties:

Name: myBtn

Location: 80,160

Text: Get Text.

Then add four more controls: two Labels and two TextBoxes. The Form should

look as the Form from Figure2.4. Note the fact that the second TextBox is ReadOnly.

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Getting started

Figure 2.4: Get text from a TextBox (1)

In order to see the way the result looks like, save the project files (File Save

All) and then run it. In this moment, even if you will press the button, nothing will

happen.

So, lets add an event for the button. Therefore, when the button is pressed, the

text from the first text box is taken and displayed in the second one. The code is

listed below.

1 p r i v a t e v oi d b u t t o n 1 _ C l i c k (o b j e c t sender, E v e n tA r g s e )2 {3 s t r i n g myStr; // c r e a t e s a s t r i n g v a r i a b l e named " myStr "4 myStr = textBox1. Text; // r e t a i n s t he t e xt f rom t he t e xt box

i n t he " myStr " v a r i a b l e5 textBox2. Text = myStr; / / p ut t he t e x t f ro m t h e " m yStr "

v a r i a b l e i n o ur s ec on d t e xt box

6 }

Run the project and type a text in your first text box. Press the button and you

will obtain a form as in Figure2.5.

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Figure 2.5: Get Text from a TextBox (2)

Exercise 3: Create a form which contains two labels, one for the price and one

for VAT. When theComputebutton is clicked, the amount of VAT will be calculated

and displayed in another textBox.

Custom controls

.NET framework has the capability of creating custom controls. Therefore, the pro-

gramming model becomes easier.

You can create custom controls in the same way as you create ordinary classes.The control class can be implemented in an already created project and it can be used

later. A custom control can inherit another control which is modified by adding some

other specific features.

String concatenation

Using the same form as before and the code listed below, lets make a simple example

which takes the text "The result is " and the text from the text boxes and it displays

the result in a message box, as in Figure2.6.Although it is possible to concatenate strings using "+", the best way to do that

is by String.Format(), especially when there are more than 2 strings.

1 p r i v a t e v oi d b u t t o n 1 _ C l i c k (o b j e c t sender, E v e n tA r g s e )2 {

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Getting started

3 s t r i n g firstText = " The r e s u l t i s ";4 s t r i n g textTb1, textTb2;5 textTb1 = textBox1. Text;6 textTb2 = textBox2. Text;

7 MessageBox. Show ( String. Format (" { 0} { 1} { 2} " , firstText,textTb1, textTb2 ) ) ; / / t h e same a s \ t e x t s l { f i r s t T e x t +te x tTb 1 +" "+ te x tTb 2 }

8 }

Figure 2.6: String concatenation

Numerical variables

Suppose that a variable contains a numerical value. Display the value in a message

box.

1 p r i v a t e v oi d b u t t o n 1 _ C l i c k (o b j e c t sender, E v e n tA r g s e )2 {3 i n t myNumber = 2 5 ;4 MessageBox. Show ("My n umbe r i s " + myNumber ) ;5 }

When you try to display the number by using the above code, you can observe

that it generates errors. Why is that? The MessageBox displays only text and your

variable is integer. C# does not convert a number in string without this action being

specified. In order to correct the problem, the number should be converted to string

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as follows.

1 p r i v a t e v oi d b u t t o n 1 _ C l i c k (o b j e c t sender, E v e n tA r g s e )2 {3 i n t myNumber = 2 5 ;4 MessageBox. Show ("My n umbe r i s "+my Nu m be r. ToString() ) ;5 }

2.2 Multiple forms applications

Generally, the applications contain more than one form. There exists a main form

from where you can start to navigate through the secondary ones. Thus, create a new

Windows Form Application which contains a form consisting of a button. When the

button is pressed another form should be opened. How can we do this?

In order to add a new form to the project, select Project Add Windows Form.

Now, you have a project containing two forms. But how will you connect them?

Add a button with any properties to your first form. The forms are represented by

classes. Thus, the object of the first form is automatically created when the program

is started. For the second one, it should be manually created, as follows:

1 p r i v a t e v oi d b u t t o n 1 _ C l i c k (o b j e c t sender, E v e n tA r g s e )2 {3 F o r m 2 s e c o n d F or m = new Form2( ) ; / / c r e a t e s t he for m4 secondForm. Show( ) ; / / ma ke s t h e f or m t o show up5 }

By using the above code, the second form will appear each time you will click the

button. To make the form appear only once, move the code which creates the form

outside of the method.

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Exercises

2.3 Exercises

1. Create a login window (the user and password are read from a file) which opens

a new form. The second form will contain the "Hello username!" label and the

Exit button.

2. Populate a list object with the words found on the individual lines of a file and

create a selecting and copying mechanism in another list.

3. Create a form which contains two listBoxes and two buttons. When you press

the first button, the selected item/items from the first listBox will be added to

the second one. When the second button will be clicked, all the item from the

second listBox will be deleted.

4. Create a calculator which contains three textBoxes (two of them are used for

introducing the numbers and the third one is for the result) and in a menu, the

binary operators. (Indication: use MenuStrip).

5. Create a forms which contains a TabControl with two pages. The first page has

a listBox which contains different items (for instance: car names, cities names

and so on). When an item is selected, an image will appear on the form. The

second page has two radioButton groups. Select one radioButton from the first

group and one from the second one and print the result in a MessageBox.

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Chapter 3

Threads

The task execution time depends on the task complexity, thus complex tasks require

longer execution time. Therefore, in order to eliminate the process waiting time, the

concurrent task execution is required. The complex applications can split their jobs in

chunks, which can run independently and simultaneously. The chunks, called threads,

can run by themselves. A thread is defined as a sequential set of instructions designated

to execute tasks in a process. It can be compared to a sequential process. These

threads are often named light processes. However a thread can operate only as part

of a process. Thus, a process can define multiple threads allowing the simultaneous

execution of various operations.

Figure 3.1: Threads

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3. Threads

3.1 Getting started

C# is a programming language where parallel execution is allowed. The threads

are independent processes which can run in parallel. They are managed by a thread

scheduler which allocates almost the same execution time to each thread. The thread

scheduler makes sure that the CPU time is not consumed by the waiting or blocking

threads. A thread can be in one of the following states: Unstarted(created), Started,

Running, Suspended, Blocked, WaitSleepJoinorStopped.

3.1.1 Creating threads

All programs contain a main thread which represents the Main method. There are

many ways of creating threads, but the simplest one is represented by the use of a

Threadobject and of a ThreadStart delegate, where Thread is used for creating and

managing threads while ThreadStart contains the code executed when the thread is

alive. In order to use threads, the System.Threading directive must be imported.

Listing3.1 creates a thread which prints "Hello! I am a thread." in console.

Listing 3.1: Creating a thread

1 u s i n g System;2 u s i n g System. Collections. Generic;3 u s i n g System. Linq;4 u s i n g System. Text;5 u s i n g System. Threading;67 namespace Threads8 {9 c l a s s Program

10 {11 s t a t i c v oi d CreatingThread( )12 {13 Console. WriteLine (" H e l l o ! I am a t h r e ad . ") ;14 }15 s t a t i c v oi d Main (s t r i n g[ ] args )16 {

17 T h r e a d S t ar t t s = new ThreadStart ( CreatingThread ) ;18 T h r e a d m y F i r s t T h re a d = new Thread ( ts ) ;19 myFirstThread. Start( ) ;20 }21 }22 }

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Getting started

3.1.2 Naming Threads

A thread can be identified by using the Thread.Name property. The name of a thread

can be set only once. A later attempt to change the name will throw an exception.

The static Thread.CurrentThread property returns the currently executing thread.

Listing3.2contains a program which creates two threads: main and worker. When

a thread starts, it has its IsAliveproperty true till the end. If a thread is stopped, it

cannot be restarted.

Listing 3.2: Creating two threads

1 u s i n g System;2 u s i n g System. Collections. Generic;3 u s i n g System. Linq;

4 u s i n g System. Text;5 u s i n g System. Threading;67 namespace Threads8 {9 c l a s s Program

10 {11 s t a t i c v oi d Main( )12 {13 Thread. CurrentThread. Name = " main th re a d ";14 T h r e a d w o r k e r = new Thread ( Hi ) ;15 worker. Name = " w o rk e r t h r e a d ";16 worker. Start( ) ;

17 Hi ( ) ;18 Console. ReadKey( ) ;19 }2021 s t a t i c v oi d Hi ( )22 {23 Console. WriteLine (" H i f ro m " + Thread. CurrentThread.

Name ) ;24 }25 }26 }

3.1.3 Join and Sleep methods

There are cases where a thread should wait for another thread to finish its task. This

can be done by using the Join method. The thread which calls Join() will be in

the waiting state until the other threads finish. In order to understand the Join()

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3. Threads

statement, the example from listing3.3 will be considered.

Listing 3.3: Join method

1 u s i n g System;2 u s i n g System. Collections. Generic;3 u s i n g System. Linq;4 u s i n g System. Text;5 u s i n g System. Threading;67 namespace Threads8 {9 c l a s s Program

10 {11 s t a t i c v oi d Main( )12 {13 Thread. CurrentThread.Name = " main th re a d ";

14 T h r e a d w o r k e r = new Thread ( Hi ) ;15 worker.Name = " w o rk e r t h r e a d ";16 worker.Start( ) ;17 worker.Join( ) ;18 Hi ( ) ;19 }2021 s t a t i c v oi d Hi ( )22 {23 f o r (i n t i = 1 ; i


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Synchronization

In some other cases maybe, a thread should wait a period of time. This can

be achieved by calling the Sleep method which will pause the thread for a specified

amount of time.

1 Thread. Sleep (1 0 0 0 ) ; / / p a us es t he t hr ea d f o r 1 00 0 m i l l i s e c o n d s2 Thread. Sleep ( TimeSpan. FromHours (2 ) ) ; // p au se s t he t hr ea d f o r 2

h o u rs

When the Sleep and Join methods are called, the corresponding threads do not

consume CPU resources.

3.2 Synchronization

The synchronization enables the programmer to control the access to shared resources.

The best way is to try to avoid synchronization, but this is not possible all the time.

There are applications where two or more threads should access the same data or

execute the same piece of code. Thus, in these kind of applications, synchronization

is necessary. This is because only one thread can access or change the data at a time.

3.2.1 Locking

In threading programs, the use of locking is necessary. Executing the same code by

different threads at a time can make the program unreliable. Lockingis used to ensure

that a shared resource is not accessed by more than one thread at a time. When a

thread wants to enter a portion of locked code, it is blocked until the resource is

released.

Thus, the use of lock statement ensures that a thread not access a block while

another thread is already in that section, called critical section. When a thread wants

to access a locked block, it will wait till the block will be released. By callingEnter,

the block will be locked and the lock will be released by calling, at the end of the

block,Exit.The lock syntax is the following:

1 l o c k( expression )

2 {

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3. Threads

3 instructions;

4 }

When we are talking about blocking threads, we are thinking of threads whose

execution is paused due to some reasons (for instance, Sleep()call or waiting a thread

to end). ThreadStatechecks the state of the thread (if it is blocked or not).

1 b o o l isblocked = (my Th re ad . ThreadState & ThreadState. W a i t S l e e p J oi n )

!= 0 ;

Thread unblocking can be performed by calling Thread.Interrupt or Thread.Abort.

Another way is represented by the specification of a timeout. If a thread execution

is paused by using the (deprecated) Suspend method, it is not considered as being

blocked anymore.

3.2.2 Monitor

A Monitoris an advanced version ofLock. It performs the same action as Lock, but

the shared data is synchronized at run time. The mutual exclusion is automatically

provided by Monitor, while Lock just focuses on it. Moreover, the Monitor has the

Wait and Pulsecommand which prevent spinning. Thus, Wait is used to block the

thread until it receives a notification from another thread while Pulse provides the

notification.

1 Monitor.Enter (mo n ) ;2 t r y3 {4 // s yn c hr o ni z ed r e g io n f o r o bj5 }6 f i n a l l y7 {8 Monitor.Exit (mo n ) ;9 }

TheMonitorsare used to ensure that when a thread performs a read/write/increment

operation, no one of the other threads does the same. A Monitor is actually a lock

attached to a resource in order to prevent the parallel use of the resource. When a

thread holds a Monitor, no other thread can hold it. All the other threads that want

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Synchronization

to use the lock are blocked and they have to wait till the thread releases the lock.

The Monitorclass contains methods for controlling the threads synchronization.

They may allow the declaration of critical areas, where, at a time, only one thread canoperate. When you want to start synchronization, call theEnter method, specifying

the object which will be blocked. If the Monitoris not available, it means that another

thread is currently in the critical region of the respective object. The critical area can

be closed by using Exit(). The compiler places the Exit() method in the final section

of a try block, so the monitor is released if an exception is thrown.

3.2.3 Mutex

AMutexis different than a C# lock because it can be used for synchronizing betweenmultiple processes. A Mutex, with a name assigned to it, is known by the operating

system and is shared between different processes. Thus, a Mutexcan be defined in

different processes.

It is used to ensure that, at some time, only a certain piece of code is executed. In

order to obtain the lock, the WaitOnemethod is used and in order to release it, the

ReleaseMutexis used.

Create a form application which contains a button. When the button is clicked, a

new mutex instance will be created. If two instances with the same name exist, the

application exits. The code is presented in the following:

1 b o o l _new;2 M u te x m u te x = new Mutex (f a l s e , " s t r i n g name ", out _new ) ;3 i f ( !_new )4 {5 MessageBox. Show (" O nly o ne i n s t a n c e c an be s t a r t e d ! ") ;6 Application. Exit( ) ;7 r e t u r n;8 }

3.2.4 Semaphore

TheSemaphoreclass is very similar to Mutex, only that, the number of threads which

have access to a shared resource can be set. The semaphore has two arguments: the

number of slots that are initially available and the maximum number of slots.

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3. Threads

When the capacity is one, the semaphore is similar to Mutex. However, a semaphore

can be released by any thread, while a Mutex or a Lockcan be released only by the

thread which holds it.The semaphores can be used to limit the competition. This means that, a particular

piece of code cannot be used by too many threads simultaneously.

Note: In .NET 4.0, the Semaphore and SemaphoreSlim classes are available.

The following code creates a semaphore with a maximum of four slots. The initial

count is 0, which means that the main thread holds the semaphore.

1 s t a t i c S e m a p h o re m y S e m = new Semaphore ( 0 , 4 ) ;

The methods for locking and releasing are the same as for Mutex, namely the

Wait() and the Release() methods.

Example:

Listing 3.4: Synchronization using semaphore

1 c l a s s Program2 {3 s t a t i c i n t threadNr = 1 0 ;4 s t a t i c i n t semCount = 5 ;56 s t a t i c v oi d Main (s t r i n g[ ] args )7 {

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Exercises

3.3 Exercises

1. Create another thread besides the main thread. Both of them will display the

numbers from 1 to 10 in the same time.

2. Modify the first exercise so that the main thread waits for the other one to finish

before starting his job.

3. Modify the first exercise so that the main method will display a new number at

every 3 seconds and the other thread at every 1 second.

4. Modify the third exercise so that when the created thread finishes, the main

thread will stop.

5. Create another two threads besides the main thread. Then increment on each

thread a value and on each increment make a sleep.

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3. Threads

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Chapter 4

Database

4.1 Getting started

ADO.NET (Active Data Objects for .NET) is a .NET Framework component which

allows the connection to various data sources, data retrieval and manipulation. Usu-

ally, the data source can be a database, but it can also be a text file, Excel, XML or

Access. In the traditional databases, the connection is maintained during the entire

process. Using ADO, working with databases can be performed while connected or

disconnected. Disconnected means that the applications can connect to the database

only for retrieving or updating data. In this case, the number of simultaneous open

connections can be reduced.

Figure 4.1: ADO architecture. Source: [1]

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4. Database

Figure 4.2: Creating a database in C#

4.1.1 Connection

It represents the creation of a connection to the database. The connection types are:

the SqlConnection object, designed for SQL Server 7.0 or later,

the OleDbConnection object, designed for Microsoft Access and Oracle.

All the information required for establishing a connection with the database are

provided by the Connection object.

Opening database connection:

1 u s i n g System. Data. SqlClient;2 . . .3 S q lC o n n e c t i o n m y C o n=new SqlConnection (" Data Source=serverDb ;

Databas e=dbName; User ID=us er Id ; Password=pass ") ;4 myCon. Open( ) ;5 . . .

Where:

serverDb is the MSSQL server host;

dbName is the name of the database;

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Getting started

userId is the user name;

pass is the user password.

Methods

1. Open(): opens the database connection;

2. Close(), Dispose(): close the database connection;

3. BeginTransaction(): used for executing a transaction. At the end call the Com-

mit or Rollback methods;

4. ChangeDatabase(): changes the database with a new one from the same server;

5. CreateCommand(): creates a valid command.

4.1.2 Commands

The command objects are used for executing commands on the database. They can

execute SQL commands, such as: SELECT, INSERT, UPDATE or DELETE. It is

mandatory that the connection to the database to be open.

1 S q lC o m m a n d c m d = new SqlCommand ("SELECT FROM dbName ", myCon ) ;

Methods

1. Constructors: a command object can be created through a constructor call;

2. Cancel(): stops a command;

3. Dispose(): kills the command object;

4. ExecuteNonQuery(): executes a command which does not return a set from the

database;

5. ExecuteReader(): executes the command from the CommandText property and

returns a DataReader object;

6. ExecuteScalar(): returns a single value from the database query.

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4. Database

4.1.3 DataReader

The data from a database can be read by usingDataReader. It is a read-only command

and in order to modify data in a table DataSet+DataAdapter should be used.

4.1.4 DataSet and DataAdapter

After setting up the connection to the database, the records from the database should

be retrieved. The data retrieved from the database is held in a DataSet, which is filled

with records by using DataAdapter. The DataAdapter command is used because the

DataSet and the Connection cannot see each other.

Two objects should be created:

1 D a ta S et d s = new DataSet( ) ;

2 S ql D a t a A d a p t er d a = new SqlDataAdapter ("SELECT from myTable" ,

my Co n )

* symbol means "all the records".

Further, the DataSet is filled by using da.Fill(ds, "MyTable").

4.1.5 DataTable

DataTable is used for storing tables, which can differ from a database table. Therefore,

if a line is modified, added or deleted, the data table within the database is not

modified. The line will just be marked as being modified, added or deleted. In order

to accept the modifications, the DataTable.AcceptChanges() method can be used.

4.1.6 DataRelation

DataRelation is used for creating parent-child relations between two tables. For in-

stance:

1 myDS. Relations.A dd (my DS . Tables[" T a b l e1 "] . Columns[" id "] , myDS.Tables

[" T a b l e 2 "] . Columns[" id "] ) ;

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My first database

4.2 My first database

Next, you will learn how to create a relational database by using Visual Studio. The

database will contain two tables: Universitiesand Faculties.

Before creating the project, launch SQL Server Configuration Management from

Start Programs Microsoft SQL Server 2008 Configuration Toolsand check if

the SQL Server is running. This action must be performed because of the fact that

the database is hosted by SQL Server.

Figure 4.3: Creating a database in c#

Then, create a Windows Form Application called myDatabase and right click on

Solution Explorer. Next, select Add New Item Service-Based Database, as in

Figure4.3. Now, you have created a database. In order to configure your database

expand the Server Explorer menu (as mentioned in Chapter 1, the menu can be made

visible by clicking on View Solution Explorer). In the database, right click on

Tables and then select Add New Table. Then, create two tables with the structure

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4. Database

Table 4.1: Universities

Column name Data type Allow Nulls

Id int NoNameUniv text NoCity text NoCode int No

Table 4.2: Faculties

Column name Data type Allow Nulls

Code int NoNameFac text No

presented in the tables4.1 and 4.2:

A unique Primary Key, identifying a particular row, can be set by right clicking

on the desired row.

Save the tables and name them as Universitiesand Faculties. Now, lets add some

data in our tables. Right click on your Table, then selectShow Table Dataand fill in

the columns. For filling the cells click inside them. Warning symbols can be observed.

They appear only when the data has changed. Save your tables by clicking Execute

SQL(marked by a red exclamation mark !). Now you have created your first database.

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My first database

4.2.1 Connect to the MS SQL Server Express Database

Listing 4.1: Connect to the SQL Server Express Database

1 u s i n g System. Data. SqlClient;23 namespace myDatabase4 {5 p u b l i c partial c l a s s Form1 : Form6 {7 p u b l i c Form1( )8 {9 I n i t i a l i z e C o m p o n e n t( ) ;

10 }1112 p r i v at e v oi d Form1_Load (o b j e c t sender, E v e n tA r g s e )13 {

14 S q l C o n n e c ti o n m y C o n=new S q l C o n n e c t i o n( ) ; / / s e t up a SQLC on n ec t io n o b j e c t

15 }16 }17 }

After you set up the Connection object, the ConnectionString property can be

accessed. Thus, selectData Show Data Sourceand then Add New Data Source

Database Dataset. You are new able to Choose your Data Connection.

You will see the window illustrated in Figure 4.4.

If you do not find any connection or you want to use a new one, click the NewConnectionbutton and then selectMicrosoft SQL Server Database File,Continueand

then browse to the database location.

You will find the seeking string (example: "Data Source=.

SQLEXPRESS;AttachDbFilename=DataDirectory

Database1.mdf;Integrated Security=True;User Instance=True") by expandingConnec-

tion String.

After your SqlConnection line, add the following code:

1 myCon. ConnectionString=" Data So ur ce =.\SQLEXPRESS; AttachDbF ilen ame =|

Da ta Dire c to ry |\ Da ta ba s e 1 . mdf ; In t e g r a te d S e c u ri ty =T ru e ; Us e r

In s ta n c e =T ru e ";

When you add this code in C# you will notice that errors are signaled. This

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4. Database

Figure 4.4: Choose your Data Connection

happens because the backslash is considered to be a special character in C# and it

should be marked. This can be done as in one of the following cases:

1 myCon. ConnectionString=" Data So ur ce =.\\SQLEXPRESS; AttachDb Filen ame

=|Da ta Dir e c to ry |\ \ Da ta b as e 1 . mdf ; In te g ra t e d S e c u ri ty =T ru e ; Us e r


1 myCon. ConnectionString=@ " Data So ur ce =.\SQLEXPRESS; AttachD bFile name

=|Da ta Dir e c to ry |\ Da ta b as e 1 . mdf ; In te g ra t e d S e c u ri ty =T ru e ; Us e r


Next, you can open a connection to the database by using myCon.Open() and you

can close the connection by using myCon.Close().

Now, lets see a simple example. Considering the relational database already cre-

ated, display in a ListBox all the Universities, in a TextBox the university code and

in another the corresponding faculty.

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My first database

Listing 4.2: Example

1 p r i v at e v oi d Form1_Load (o b j e c t sender, E v e n tA r g s e )2 {

3 myCon. Open( ) ;4 dsUniv = new DataSet( ) ;5 dsFac = new DataSet( ) ;67 dsUniv = new SqlDataAdapter ("SELECT f r om U n i v e r s i t i e s ",

my Co n ) ;8 daUniv. Fill ( dsUniv , " U n i v e r s i t i e s ") ;9

10 daFac = new SqlDataAdapter ("SELECT f r om F a c u l t i e s ", myCon );

11 daFac. Fill ( dsFac, " F a c u l t i e s ") ;1213 f o r e a c h ( D a ta R o w d r i n dsUniv. Tables[" U n i v e r s i t i e s "] . Rows )14 {

15 S t ri n g n a me = dr. ItemArray. GetValue (1 ) .ToString( ) ;16 listBox1. Items.A dd ( name ) ;17 }18 }1920 p r i v at e v oi d l i s t B o x 1 _ S e l e c t e d I n d e x C h a n g e d (o b j e c t sender, EventArgs

e )21 {22 S t r i n g U n i v S e l e c te d = listBox1. SelectedItem.ToString( ) ;2324 f o r e a c h ( D a t aR o w d r i n dsUniv. Tables[" U n i v e r s i t i e s "] .Rows )25 {26 i f ( UnivSelected == dr.ItemArray.GetValue (1 ) .ToString( ) )

27 {28 textBox1. Text = dr .ItemArray.GetValue (2 ) .ToString( ) ;29 code = Convert. ToInt16 ( dr.ItemArray.GetValue (2 ) ) ;30 }31 }3233 f o r e a c h ( D a t aR o w d r i n dsFunctii. Tables[" f u n c t i i "] .Rows )34 {35 i f ( code == Convert. ToInt16 ( dr .ItemArray. GetValue ( 0 ) ) )36 {37 textBox2. Text = dr .ItemArray.GetValue (1 ) .ToString( ) ;38 }39 }40 myCon. Close( ) ;

41 }

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4. Database

4.3 Exercises

1. Using the database already created, insert and delete a new record to/from the

database. Next, modify and search an existing record.

2. Create a relational database named myDatabase with two tables. Then insert by

code at least 6 lines for each table. The values will be read from the keyboard.

Implement a WindowsApplication which allows the user to insert and delete a

record.

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Chapter 5

Web Services

A web service is a collection of protocols and standards used for communicating be-

tween two devices via Internet. It is based on the client-server model thus: the server

exposes some methods and the client connects to the server in order to use the meth-

ods. The idea is to create components such as black boxes that can interact, without

taking into account the operating system or programming language. More precisely,

the web service is a component or a module of executable code with a special interface

that makes the methods to be available for other programs using a HTTP request.

The request is made by using HTTP GET, HTTP POST and Simple Object AccessProtocol (SOAP).

Figure 5.1: Web Services Triangle Architecture. Source: [2]

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5. Web Services

Therefore, the methods or the messages can be published in order to be used

from everywhere. For coding the data, web service uses Extensible Markup Language

(XML) and for transporting it, an XML-based protocol called SOAP [4]. SOAP isused in applications which need to exchange information over HTTP. A web service

can be located by using Web Service Definition Language (WSDL).

5.1 Getting started

Note: All the examples are done by using Visual Studio 2010 Ultimate. Starting

with .Net Framework 4.0, ASP.NET Web Service Application template is not available

anymore. However, you can create a web service targeting the .NET Framework 3.5

as in figure5.2. Then, you can reuse .NET Framework 4.0 by re-targeting to .NET

Framework 4.0 from the project properties.

Figure 5.2: Creating a Web Service

In order to create a new web service, fire up Visual Studio. Then, there are two

possibilities: either select the New Projectbutton or create the project from the menu

bar as follows File New Project Visual C# Web ASP.NET Web Service

Application. After creating the project, all the project files can be found in Solution

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Getting started

Explorer (see Figure5.3).

Figure 5.3: Solution Explorer

Notice that the wizard has created a project which contains the Service1 class with

the following implementation.

Listing 5.1: Hello WorldWeb Service

1 u s i n g System;2 u s i n g System. Collections. Generic;3 u s i n g System. Linq;4 u s i n g System. W eb ;5 u s i n g System. W eb . Services;6

7 namespace WebService18 {9 // /

10 / // Summary d e s c r i p t i o n f o r S e r v i c e 111 // / 12 [WebService ( Namespace = " http :// tempuri . org /") ]13 [W e b S e r v i c e B in d i n g ( ConformsTo = WsiProfiles. B a s i c P r o f i le 1 _ 1 ) ]14 [System. ComponentModel. ToolboxItem (f a l s e) ]15 // To a l lo w t h i s Web S e r vi c e t o b e c a l l e d fr om s c r i p t , u si n g

ASP.NET AJAX, uncomment the fo ll ow in g l i n e .16 / / [ S ys te m . Web . S c r i p t . S e r v i c e s . S c r i p t S e r v i c e ]17 p ub l ic c l a s s Service1 : System.W eb .Services. WebService18 {

19 [WebMethod]20 p u bl i c s t r i n g HelloWorld( )21 {22 r e t u r n " He l lo W orld " ;23 }24 }25 }

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5. Web Services

The class contains one method named HelloWorld(). For the method to be sent

by the web service to the client, it should be declared as web method through the

[WebMethod] directive.

1 [WebMethod]2 p u bl i c s t r i n g HelloWorld( )3 {4 r e t u r n " He l lo W orld " ;5 }

Lets add another method. For instance, we want to compute the sum of two

numbers. For doing so, we implement a method as follows:

1 [WebMethod]2 p u bl i c i n t Ad d (i n t a, i n t b )

3 {4 r e t u r n a+b ;5 }

By building and running the project, we will have our first web service like in the

Figure5.4.

Figure 5.4: Web Service

Note: Each method has to be marked with the [WebMethod] directive. Without

this directive, the method cannot be called.

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Create a Web Service client

5.2 Create a Web Service client

In order to create a client, fire up Visual Studio and create a new Console Application

project. Name the projectmyFirstClient. Then, add a web service reference to the

client, as shown in the Figures5.5 and 5.6.

Figure 5.5: Add service reference (1)


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5. Web Services

Paste the URL into the text box URL (here http://localhost:5005/Service1.asmx).

After you press go, if the service is found you will see a window as in Figure 5.7and

then you should add the reference.


Now, the client is connected to the service and it can use the methods exposed by

the service. Further, the client can be implemented as below:

Listing 5.2: TheClient code

1 s t a t i c v oi d Main (s t r i n g[ ] args )2 {3 myFirstClient. localhost. S e r v i c e1 s e r v i c e = new

my Fi rs t Cl ie nt . localhost. Service1( ) ;4 i n t su m= service. A dd (2 ,3 ) ;5 Console. WriteLine (" The sum i s "+su m.ToString() ) ;6 Console.ReadKey( ) ;7 }

Exercise: Create another client for making use of your service.

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Exercise

5.3 Exercise

1. Create a web service which converts the temperature from Fahrenheit to Celsius,

and vice versa. Then create two clients (one Console Application and one Form

Application) for making use of your service.

2. Create a web service which provides the exact date and time of the service.

3. Create a Web Service that gives access to a database which stores information

about Romania. Then, create a client which uses the service. It will provide

methods for adding new cities and for modifying them, based on a given name.

4. Make a presentation about Windows Communication Foundation.

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5. Web Services

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Chapter 6

Windows Presentation

Foundation

The Windows Presentation Foundation (WPF), designed by Microsoft, is a framework

for creating user-friendly interfaces. Initially, it was part of .NET Framework 3.0, being

known as "Avalon". WPF uses Extensible Application Markup Language (XAML),

an Extensible Markup Language (XML) derivative for initializing structure values

and objects. It provides the possibility of building UIs, 2D graphics, 3D graphics,

documents and multimedia applications. Standalone and also XAML Browser WPF

applications can be developed by using a similar programming model.

WPF makes much more than what Windows Form can do because it is an unified

solution which contains different technologies. For example, if you want to develop a

Windows Form Application which displays video or audio, you should use also Win-

dows Media Player. Or, if you want to display documents on an interface, you can use

Windows Forms, but for fixed-format document you must use Adobes PDF. WPF

has support for all these and even more.

The WPF goal is not to replace Windows Forms. Windows Forms will have also

valuable usability even in WPF world and many applications will continue to use them

while some others will connect Windows Forms with WPFs.

WPF can create modern interfaces in a fairly straightforward manner. Compared

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6. Windows Presentation Foundation

to Windows Form applications, the WPFs are divided in two parts:

the appearance of an user interface, specified in XAML,

the behavior, implemented using C#or Visual Basic.

6.1 Getting started

A WPF application can be implemented using Visual Studio, 2008 version or later.

The Visual Studio 2005 users can also develop WPF applications by installing an

add-on.

A simple WPF application can be created by selecting File New Project

Visual C# WPF Application. A window as in Figure6.1 will appear. The project

can be renamed and also its location can be changed.

Figure 6.1: Creating a WPF Application

The project along with the MainWindow.xaml and App.xaml files are created by

Visual Studio. It has almost the same structure as Windows Form, excepting that the

Window1.designer.cs file is now declared in XAML as MainWindow.xaml.

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Getting started

6.1.1 Controls

The Toolbox (Ctrl+W,X) contains a rich set of built-in controls. They can be drag and

dropped from the toolbox or they can be implemented by using XAML code. Listing

6.1 shows the XAML code automatically generated when the project is created. It

provides the ability to create, configure, show, and manage the lifetime of windows

and dialog boxes.

Listing 6.1: The structure of a WPF program

1 5 6 7 8 9

10 11

Buttons

Figure 6.2: WPF button

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First control presented is the well known button (see Figure 6.2). It has two main

properties: IsDefault and IsCancel.

Exercise 1:

Using the application already created, add a button, named MyBut-ton, to the window. Then, in the properties window, after switching to the event view,

double-click on the "Click" event.

In this way, the method button1_Click, which will be executed when the button

is pressed, is automatically created. This can be done only if the Service Pack 1 for

Visual Studio is installed. The same result will be achieved if the button will be

double-clicked. The method created in the code-behind file is the same as in Windows

Form.

Add inside the method the code: MessageBox.Show("Hi!"). Then, test the appli-

cation which is also presented in Listing 6.2.

Listing 6.2: Button event

1 u s i n g S ys te m;2 u s i n g S ys te m.C o l l e c t i o n s. G e n e r i c;3 u s i n g S ys te m.Linq;4 u s i n g S ys te m.Text;5 u s i n g S ys te m. Windows ;6 u s i n g S ys te m. Windows .C o n t r o l s;7 u s i n g S ys te m. Windows . Data ;8 u s i n g S ys te m. Windows .Documents;9 u s i n g S ys te m. Windows .In p u t;

10 u s i n g S ys te m. Windows .Media;11 u s i n g S ys te m. Windows .Media.Imaging;12 u s i n g S ys te m. Windows .N a v i g a t i o n;13 u s i n g S ys te m. Windows .Shapes;1415 namesp ace MyFirstWPF16 {17 p u b l i c p a r t i a l c l a s s MainWindow : Window18 {19 pu bl ic MainWindow( )20 {21 I n i t i a l i z e C o m p o n e n t( ) ;22 }

2324 p r i v a t e v o i d b u tt o n1 _ Cl i ck (o b j e c t s en de r, RoutedEventArgs e )25 {26 MessageBox. Show (" Hi ! ") ;27 }28 }29 }

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Getting started

The XML button code is listed in the following.

Listing 6.3: XML button code

1 5 6 7 8 9

10 11 12

TextBoxes and RichTextBoxes

A TextBox can be used for displaying unformatted text or for giving the possibility of

entering some text. It brings the opportunity of words auto-correcting by using the

spell checking functionality. The available languages are English, French, German and

Spanish. The code for enabling the spell checking functionality is presented below.

This can be done by setting the SpellCheck.IsEnabled property to true.

1

The table6.1 presents other WPF controls.

Table 6.1: Other controls

Label displays text

ListBox displays a list of items

CheckBox displays item that can be selected or clearedComboBox items control where only one item can be visible at a time

RadioButton displays items that can be selected but not cleared

TabControl displays multiple items that share the same space in a form

Image displays an image

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6.1.2 Layouts

In WPF, the layouts are used for arranging controls in complex environments. The

Table6.2 presents the most popular build-in layout panels.

Table 6.2: Layouts

Stack Panel places the controls beside each other or below

Dock Panel arranges the elements in the right, left, bottom, top or center of

the panel

Wrap Panel as StackPanel, except that, when the line finishes, the child ele-ments can be wrapped to new lines

Grid Panel organizes the child in a tabular structure

Canvas Panel the childs coordinates are explicitly given

6.2 Styling and Data Binding

6.2.1 WPF vs Windows Forms

The main difference between Windows Forms and WPF applications is the way User

Interface (UI) elements are displayed and populated. WPF introduces the idea of

element styling and data binding in order to simplify the production process.

Lets consider the following problem: a main window with about 10 Slider items.

All sliders should be in the range 128 to 200 and be 250px in width and 30px in height.

Also, a numerical display, in the form of a TextBox control, should be added to show

the current selected value and modify the slider value. All the data from the sliders

should be saved as an object properties.

In order to solve the problem in Windows Forms, the designer would have to

manually set the Minimum, Maximum, Width and Height properties on each slider in

order to set the appearance, making further modifications very hard. On a functional

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Styling and Data Binding

level, one must add event handlers to the sliders in which the TextBox.Text property

would be updated and also, assign each sliders value to the respective object property.

WPF brings two new concepts in order to solve these problems: Styling and DataBinding.

6.2.2 Styles

The concept of styles let you remove all properties values from the individual user

interface elements and combine them into a style. A style consists of a list of setters.

If you apply this style to an element, it sets all properties with the specified values.

The idea is quite similar to Cascading Styles Sheets (CSS) that we know from web

development.To make the style accessible to your controls you need to add it to the resources.

Any control in WPF has a list of resources that is inherited to all controls beneath the

visual tree. That is the reason why we need to specify a x:Key="myStyle"property

that defines a unique resource identifier.

In this way, the modifications to all the controls can be made in a single place. For

example, setting the properties to the slider controls can be done as following.

At the beginning of the tag, the style definition must be added.

1 2 3 4 5 6 7 8

This defines the SliderStyle1 style which can then be applied to controls of type

Slider. Assigning a style to a control is done by adding the Style property to the

control definition:

1

Multiple sliders can have the same style assigned. This solves the problem of

modifying a property in several controls.

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Listing 6.4: Example with multiple sliders

1 5 6 7 8 9

10 11 12 13 14 15

16 17 18 1920 21 22 23 24 25 26 27 28

29

30

31 32 33

34

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Styling and Data Binding

Name=" textbox 3 "/>36 37

38 39 40

6.2.3 Data Binding

WPF provides a simple and powerful way to auto-update data between the business

model and the user interface. This mechanism is called DataBinding. Every time

when the data of your business model changes, it automatically reflects the updates

to the user interface and vice versa. This is the preferred method in WPF for bringing

data to the user interface.

DataBinding can be unidirectional (source target or target source) or bidi-

rectional (source target).

Data Binding between UI Elements

The issue of displaying the slider value in a TextBoxand be able to modify data in

both directions is much simpler to be solved in WPF. To bind a TextBoxcontrol to a

Slider, the TextBox.Text property must be binded to the Slider.Valueproperty.

1

In order to implement this, the Text property contains a binding definition.

ElementNamerefers to the control the TextBox binds.

ThePath value represents the target object property to be displayed.

UpdateSourceTriggerrepresents the event which triggers the data exchange be-

tween the controls.

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Modesets the direction in which the data should be exchanged, in this case we

want the slider to modify the TextBoxvalue and vice versa.

The binding mechanism also allows formatting the string displayed in the TextBox

and different data conversion techniques which are out of the scope of this laboratory.

6.3 Animations

Test the application from Listings 6.5 and6.6.

Listing 6.5: XML code

1 5 6 7 9 10 < E l l i p s e. F i l l>11

12 13 14 15 16 < E l l i p s e. RenderTransform>17 19 20 21 22 23

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Animations

Listing 6.6: C#code

1 u s i n g S ys te m;2 u s i n g S ys te m.C o l l e c t i o n s. G e n e r i c;

3 u s i n g S ys te m.Linq;4 u s i n g S ys te m.Text;5 u s i n g S ys te m. Windows ;6 u s i n g S ys te m. Windows .C o n t r o l s;7 u s i n g S ys te m. Windows . Data ;8 u s i n g S ys te m. Windows .Documents;9 u s i n g S ys te m. Windows .In p u t;

10 u s i n g S ys te m. Windows .Media;11 u s i n g S ys te m. Windows .Media.Imaging;12 u s i n g S ys te m. Windows .N a v i g a t i o n;13 u s i n g S ys te m. Windows .Shapes;1415 namespace Animation16 {

17 / // 18 / // I n t e r a c t i o n l o g i c f o r M ainWindow . x am l19 / // 20 p u b l i c p a r t i a l c l a s s MainWindow : Window21 {22 pu bl ic MainWindow()23 {24 I n i t i a l i z e C o m p o n e n t ( ) ;25 Compositi onTarget . Rendering += Move ;2627 }2829 I n t3 2 c o un t er = 0 ;

30 v o i d Move ( o b j e c t s e n d e r , E ve n tA r gs e )31 {32 c o un t er = c o un t er + 2 ;33 C an va s . S e t L e f t ( b a l l , c o u n te r ) ;34 }35 }36 }

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6.4 Exercises

1. Create a login window which opens another form (the user and password are

read from a file). The second form will contain a "Hello username!" label and

the Exit button.

2. Make an application that changes an object color depending on some parameters

RGB.

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Bibliography

[1] MSDN, http://msdn.microsoft.com/en-us/library/67ef8sbd.aspx. vii,39

[2] W. S. T. Architecture, http://www.flickr.com/photos/dullhunk/415645479/.vii,

49

[3] C. in C#, http://www.c-sharpcorner.com/. 8

[4] W. Services, http://www.w3schools.com/webservices/ws_why.asp. 50

[5] http://www.wpftutorial.net/.

[6] Wikipedia, http://en.wikipedia.org/wiki/main_page.