Computer Application in Industrial Engineering: Programming C# for Engineers

1. DR ATIF SHAHZAD
Computer Applications
in Industrial Engg.-I
IE-322
LECTURE #07

2. Computer Applications in
Industrial Engg.-I
IE322

3. …Recap
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4. Recap
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A Random Review
A quick Question
Classes
• Class vs Object:
Examples
• Class vs Object:
Adding a Class to a C#
project
Declaring a Class
Adding a Method to the
Class
Instantiating an object
of a class
Calling a Method of an
object
Complete Example—
class Car
Solution Explorer
Files of the project in
Windows explorer
Example2:
Some built-in classes
A BonusTopic
• Look this example
• Conditional Operator
What is aVisual Studio
Project?
What is aVisual Studio
Solution?
Project & Solution

5. What we will see…
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Class Example Fields Encapsulation
Access
modifiers
Properties Value keyword
Auto-
implemented
properties
Constructors

6. A quick Question
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The process of creating objects is called:

7. A quick Question
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The process of creating objects is called:
Instantiation

8. More on Classes
IE322

9. Class Example
class Person
{
int age;
string name;
public void SayHi()
{
Console.WriteLine("Hi");
}
}
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10. Class Example
class Person //declares a class named Person
{
int age;
string name; // age and name fields
public void SayHi() // a SayHi method
{
Console.WriteLine("Hi");
}
}
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11. Fields
class Person //declares a class named Person
{
int age;
string name; // age and name fields
public void SayHi() // a SayHi method
{
Console.WriteLine("Hi");
}
}
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Filed is also called InstanceVariable

12. Fields
class Person //declares a class named Person
{
int age;
string name; // age and name fields
public void SayHi() // a SayHi method
{
Console.WriteLine("Hi");
}
}
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13. Instantiate an object
static void Main(string[] args)
{
Person p1 = new Person();
p1.SayHi();
}
//Outputs "Hi"
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The new operator
• instantiates an object &
• returns a reference to its location

14. Use Classes
static void Main(string[] args)
{
Person p1 = new Person();
p1.age=19;
p1.SayHi();
}
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you can use the dot operator to
make an assignment when valid.

15. Encapsulation
IE322

16. Encapsulation
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"surrounding" an entity, not just to
keep what's inside together, but also
to protect it.
Encapsulation is also
called information hiding.

17. Why Encapsulation?
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17
Not only to combine but also to restrict
access to the inner workings of that class.
Encapsulation is also
called information hiding.

18. Implementing Encapsulation
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Implemented by using access modifiers.
An access modifier defines
the scope and visibility of a
class member.

19. Encapsulation: Example
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class BankAccount
{
private double balance=0;
public void Deposit(double n)
{
balance += n;
}
public voidWithdraw(double n)
{
balance -= n;
}
public double GetBalance()
{
return balance;
}
}

20. Encapsulation: Example
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class BankAccount
{
private double balance=0;
public void Deposit(double n)
{
balance += n;
}
public voidWithdraw(double n)
{
balance -= n;
}
public double GetBalance()
{
return balance;
}
}

21. Why Encapsulation?
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Control the way data is accessed or
modified.
Code is more flexible and easy to change
with new requirements.
Change one part of code without affecting
other parts of code.

22. Encapsulation--Question
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_____Person
{
private int age;
_____int GetAge()
{
______age;
}
public void SetAge(int n)
{
age = n;
}
}
Fill in the blanks to declare a
Person class, hide the age
member, and make it
accessible through the
GetAge method.

23. Encapsulation—Question--Solved
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class Person
{
private int age;
public int GetAge()
{
return age;
}
public void SetAge(int n)
{
age = n;
}
}
Fill in the blanks to declare a
Person class, hide the age
member, and make it
accessible through the
GetAge method.

24. Properties
IE322

25. Properties
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We just saw that: It is a good
practice to encapsulate
members of a class and
provide access to them ONLY
through public methods.

26. Properties
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Field
• A protected member
of a class
Accessors
• Special method to
access the fields

27. Why Properties?
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So, why use properties?
Why not just declare the
member
variable public and access it
directly?.

28. Because…
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With properties you have
the option to control the
logic of accessing the
variable

29. Properties
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A property is a member that
provides a flexible mechanism
to read, write, or compute the
value of a private field.
Properties can be used as if
they are public data members,
but they actually include special
methods called accessors.
The accessor of
a property contains the
executable statements that help
in getting (reading or
computing) or setting (writing)
a corresponding field.
Accessor declarations can
include a get accessor,
a set accessor, or both.

30. set & get
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The set accessor is
used to assign a
value to the name
variable;
get is used to return
its value.

31. Because…
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It is a good practice to
encapsulate members of a
class and provide access to
them only
through public methods.

32. Example
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class Person
{
private int age=0;
public int Age
{
get
{
return age;
}// end get
set
{
if (value > 0)
age = value;
} // end set
} // endAge
} // end class Person
You can have any custom
logic
with get and set accessors.
The name of the property can be anyt
hing you want, but coding convention
s dictate properties have the same na
me as the private field with a
capital letter.

33. value keyword
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value is a special keyword,
which represents the value
we assign to a property using
the set accessor.
class Person
{
private int age=0;
public int Age
{
get
{
return age;
}// end get
set
{
if (value > 0)
age = value;
} // end set
} // endAge
} // end class Person

34. Question
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class A
{
private int x=8;
public int X
{
_______{
return x__x;
}
}
}
Fill in the blanks to
create a read-only
property X.
The return value of
the accessor should
be the square of x.

35. Question: Solved
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class A
{
private int x=8;
public int X
{
get {
return x*x;
}
}
}
Fill in the blanks to
create a read-only
property X.
The return value of
the accessor should
be the square of x.

36. Auto-Implemented Properties
When you do not need any custom logic,
C# provides a fast and effective
mechanism for declaring private members
through their properties.
public string Name { get; set; }
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37. Auto-Implemented Properties
As you can see, you do not need to declare
the private field name separately - it is created
by property automatically.
Name is called an auto-implemented property.
Also called auto-properties, they allow for easy and
short declaration of private members.
public string Name { get; set; }
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38. Auto-Properties: Example
class Person
{
public string Name { get; set; }
}
static void Main(string[] args)
{
Person p = new Person();
p.Name = “Ali";
Console.WriteLine(p.Name);
}
// Outputs “Ali"
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39. Auto-Properties: Question
class Person
{
public ____Age {____ set; }
}
Fill in the blanks to create an auto-
property named Age of type int.
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40. Auto-Properties: Question Solved
class Person
{
public int Age {get; set; }
}
Fill in the blanks to create an auto-
property named Age of type int.
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41. Constructors
IE322

42. Constructors
A class constructor is a
special member method of
a class that is executed
whenever a new object of
that class is created.
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43. Constructors
A constructor
has exactly
the same
name as its
class,
is public
does not
have any
return
type.
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44. Constructors: Example
//Person.cs
class Person
{
private int age;
public Person()
{
Console.WriteLine("Hi th
ere");
}
}
//Program.cs
static void Main(string[] args)
{
Person p = new Person();
}
// Outputs "Hi there"
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upon the creation of an object of typ Person,
the constructor is automatically called.

45. Constructors
Constructors can be very useful for setting initial
values for certain member variables.
A default constructor has no parameters.
However, when needed, parameters can be added
to a constructor.
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46. Constructors: Example
//Person.cs
class Person
{
private int age;
private string name;
public Person(string nm)
{
name = nm;
}
public string getName()
{
return name;
}
}
//Program.cs
static void Main(string[] args)
{
Person p = new Person(“Reda");
Console.WriteLine(p.getName());
}
//Outputs “Reda"
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Constructors can be overloaded like any method
by using different numbers of parameters.

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NEVER hesitate to
contact should you
have any question
Dr.Atif Shahzad