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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    CONTENTS

    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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    CONTENTS

    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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    CONTENTS

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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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    1.2 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. Console Applications

    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

    >= Greater than or equal to

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    1. Console Applications

    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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    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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    2. Windows Form Applications

    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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    2. Windows Form Applications

    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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    2. Windows Form Applications

    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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    2. Windows Form Applications

    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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    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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    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 {

    8 f o r (i n t i = 1 ; i

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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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    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

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

    1 myCon. [email protected] " 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

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

    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)

    Figure 5.6: Add service reference (2)

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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.

    Figure 5.7: Add service reference (3)

    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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    6. Windows Presentation Foundation

    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. Windows Presentation Foundation

    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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    6. Windows Presentation Foundation

    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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    6. Windows Presentation Foundation

    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. Windows Presentation Foundation

    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.